Evaporation Control 

Research, 1955-58

By ROBERT R. CRUSE and G. EARL HARBECK, JR.

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1480

Prepared in collaboration with the 

Southwest Water Evaporation Research 

Council, the Southwest Research Institute, and the Texas Board of Water 

Engineers

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1960
UNITED STATES DEPARTMENT OF THE INTERIOR 

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington 25, D.C. - Price 50 cents (paper cover)
CONTENTS

Pag«

Abstract.__ _ ______-__-_--_-_-___-______-____-_____-__________-_- 1

Introduction---___----_--____-________-___-_--__-_-___-_---__-_--_ 1

Discussion of theory____--___-_--_______-___--___-_____--_-_--__--_ 4

Laboratory investigations_________________________________________ 7

Laboratory screening of organic chemicals_.-________--_-_-_-__-__ 7

Field screening, using 10-foot tanks._____________________________ 13

Miscellaneous laboratory studies___.___________________________ 15

Bactericidal and bacteriostatic additives.____-__-_-_-_--___-__ 15

Wind studies__.____.-_________-____-__--___-_--_--_-_-__ 17

Liquid-phase application methods.__________________________ 18

Cloud-point determinations.___________________-__-.-.___-_. 19

Wick-dispenser tests.__________-____-__-__-----__--____---. 21

Pelleting of solid evaporation retardants.._____-___--______ 27

Raft design____________.._._.____.______--___---__-____-__ 28

Considerations of toxicity___.___________--_-.--_._-__._-.. 28

Large-scale field tests.__---__--_-_______--______-__--_--__---_-_--- 30

Other methods of application. ______________________________________ 37

Application in a solvent.___________-_-________-__--_--__-___-__ 3V

Application as a liquid____________________-_____-_--__-_-_---_- 39

Application as a solid._________________________________________ 39

Application as an emulsion.____________________________________ 39

Suggestions for future work_______.__________-_____-_---_____-_-_-_. 39

The effect of impurities_______________________________________ 39

Bactericides and bacteriostats.__________________________________ 40

Bacteria-resistant materials.____________________________________ 40

The effects of wind.__.---__-__-_..-______-__---___-----------_ 40

Field studies.___-__--________-___-_______-__---__--__-__----__ 41

Screening apparatus...___--_______________..___-_-__-----__.-_-_-__ 41

Technical details and specifications.___-__--___-----_-___----_--- 41

Desiccant regeneration.___-___-______________-______-----__---_ 41

Toxicity statement-_.._-_-__---_____._._.-__--__-_----------------- 42

References cited..___._____________________________--___-___----_--- 44

Index._ ___________________________________________________________ 45

in
IV EVAPORATION CONTROL RESEARCH, 1955-58

ILLUSTRATIONS

Page

PLATE 1. Screening apparatus at Southwest Research Institute..--.. 4 

FIGURE 1. Effects of molecular structure on compressibility of films of

alkanols. ________________-__-----_-____-__----------_ 5

2. Details of screening apparatus.-------------------------- 8

3. Apparatus used for determining effects of wind on a monofilm. 17

4. Cloud-point temperatures for various ethanol-dodecanol

(Lorol 7) mixtures.___________________________________ 20

5. Cloud-point temperatures for various hexadecanol (Siponol

CX)-dodecanol (Lorol 7) mixtures.___________________ 21

6. Cloud-point temperatures for various hexadecanol (Siponol

CX)-dodecanol (Lorol 11) mixtures._____________--_--_ 22

7. How to make an evaporation retarder._-________-----__--_ 23

8. Sectional view showing method of installing dripper..--__-__ 23

9. Sketch showing arrangement of instruments...------------- 24

10. Variation of flow rate of dodecanol with time, using orlon

wick (test no. 8)_____________-_-_-___-_-_-___ ----- 24

11. Variation of flow rate of dodecanol with time, using orlon

wick in copper tubing (test no. 25)__________-__--_--__- 26

12. Variation of flow rate of dodecanol with time, using nylon

wick in copper tubing (test no. 27)__.___________.-..__- 26

13. Miscellaneous raft designs-..---------------------------- 29

14. Dispensers used in Australia for large reservoirs_-___--_--__ 38

TABLES

TABLE 1. Compounds screened as evaporation retardants. _____________ 9

2. Compounds rejected as evaporation retardants.______________ 12

3. Results of tests in 10-foot tanks_---------__------_--------- 14
EVAPORATION CONTROL RESEARCH, 1955-58

By EGBERT K. CRUSE * and G. EARL HARBECK, JR.2

ABSTRACT

One hundred fifty-two compounds and compositions of matter were screened 

as potential evaporation retardants. The homologous straight-chain fatty alkanols are considered the best materials for retardants.

Several methods of application of the alkanols to the reservoir surface were 

investigated. Although wick-type drippers for the application of liquids and 

cage rafts for the application of solids appear to be the most promising methods 

from an economic standpoint, both methods have serious disadvantages.

Considerable study was given to reducing biochemical oxidation of the evaporation retardants. Copper in several forms was found adequate as a bacteriostatic agent but posed a potential hazard because of its toxicity. Many other 

bactericides that were tested were also toxic.

Two sets of large-scale field tests have been completed and several others 

are still in progress. On the larger reservoirs, the reduction of evaporation 

was not more than 20 percent under the prevailing conditions and the application procedure used.

Three major practical problems remain; namely, the effects and action of 

wind on the monofilm, the effects of biochemical oxidation, and the most effective method of application. Fundamental problems remaining include the effects 

of various impurities, and the composition of the best evaporation retardant; 

the long-range effects of monofilms on the limnology of a reservoir, including 

the transfer of oxygen and carbon dioxide; toxicological aspects of all components of any evaporation-retardant composition, plus toxicology of any composition chosen for large-scale use; and further studies of the calorimetry and 

thermodynamics involved in the mechanism of evaporation and its reduction 

by a monofilm.

INTRODUCTION

The purpose of the present investigation was to develop a practical, safe, and effective method of treating the surface of a water 

reservoir with a monomolecular chemical film to reduce losses of 

water by evaporation.

This report describes investigations made in Texas during the 

period 1955-58 on the use of a monomolecular film for the suppression of evaporation. The laboratory investigations were made by 

Southwest Kesearch Institute of San Antonio, Tex., under a con1 Southwest Research Institute.

2 U. S. Geological Survey.
2 EVAPORATION CONTROL RESEARCH, 1955-58

tract between the Institute and the Texas Board of Water Engineers, who acted as the contracting agency and fiscal agent for 

the Southwest Water Evaporation Research Council, Inc.

Funds for that part of the investigation made by Southwest 

Research Institute were contributed to the Southwest Water Evaporation Council by 86 different sponsors, among whom were municipalities, private industries especially the private electric utilities 

consulting engineers, technical societies, individuals, and other organizations.

The evaluation of the reduction in evaporation was made by 

the U. S. Geological Survey.

Technical articles from Australia in 1953 and 1955 (Mansfield, 

1953, 1955) indicated the feasibility of control of evaporation from 

reservoir surfaces by thin chemical films 1 molecule, or one tenmillionth of an inch, thick. Reductions in the rate of evaporation 

of 45 percent were expected. The method was an application of 

the principles that were originally developed by Langmuir (1917). 

A duplex film was used initially, but later, a single-component film 

was applied with better results.

The work in Australia indicated that there were few, if any, 

problems under field conditions there. Differing climatic conditions, as well as vested public and private interests in many of the 

various reservoirs, dictated that the work in Australia, promising 

as it was, should be checked under conditions prevailing in Texas 

and southwestern United States before the procedures could be generally recommended in this country. These circumstances resulted 

in negotiations leading to a project at Southwest Research Institute 

to develop and modify the Australian process for use on both public 

and private reservoirs in the United States. Results obtained from 

tests made in stock tanks indicated that biochemical degradation of 

the materials recommended by the Australians was quite severe 

under conditions in the United States. These results were confirmed 

by independent investigations conducted by the Robert A. Taft 

Sanitary Engineering Center, U. S. Public Health Service, Cincinnati, Ohio, (Ludzack and Ettinger, 1957). Further, the wind 

provided a severe problem, contrary to Australian indications. 

This problem was not so pronounced on stock tanks as it was on 

larger reservoirs, where on windy days the films were found only 

on the downwind side of the reservoirs where they were compressed, 

and extended for distances varying from 3 to 30 feet from the 

shore. This phenomenon was noted when both liquid and solid 

retardants were used.
INTRODUCTION 6

Restrictions on the use of any film-forming evaporation retardant 

are severe. The material used must not only reduce the rate of 

evaporation effectively, but it must be nontoxic to every beneficial 

kind of animal or plant using the reservoir water; it should, for 

economic reasons, be resistant to oxidation or degradation by microorganisms; it should not be detrimental to the biological balance 

of the reservoir, including effects on transfer of oxygen and carbon 

dioxide; and, as indicated by work done during this investigation, 

it should be effective in both hot and cold weather. Further, the 

cost of the process, including the initial cost of the material used, 

must be economical.

The economics of the process were promising at first. Mansfield 

(1956) estimated the cost at 2.5 cents per thousand gallons of water 

saved, based on a film life of 6 weeks and an application dosage of 

about 2.2. pounds per acre. This amount was found somewhat 

inadequate under prevailing conditions, but, using a solid retardant 

in cage rafts similar to those described by Mansfield, a dosage of 

5 pounds per acre was found more satisfactory. Based on a cost 

of materials at 40 cents per pound in 1957, a film life of 60 days 

and a saving of 2 feet of evaporation in arid regions, the calculated 

cost of water saved by the monofilm technique under conditions 

in south-central Texas is about 5 cents per thousand gallons. Field 

tests indicated that these cost figures would apply primarily in 

areas of high evaporation, but not in areas of high humidity and 

low rate of evaporation.

Two items should be mentioned in connection with these costs. 

First, in a reservoir where evaporation makes the water slightly 

brackish, even a 20 percent saving of the water that would otherwise evaporate may be sufficient to render the entire reservoir usable. 

The water that evaporates is pure water; hence, any that is kept 

from evaporating reduces the concentration of dissolved solids in 

the reservoir. Any additional evaporation reduction over that 

needed to reduce the salinity level is an extra dividend in yield of 

usable water.

Second, in many areas a reduction in evaporation may mean 

that a reservoir will contain water for longer periods. The mere 

availability of even a small amount of water may be of sufficient 

economic importance that the cost of retarding evaporation is only 

a secondary consideration.
4 EVAPORATION CONTROL RESEARCH, 1955-58 

DISCUSSION OF THEORY

This work is an outgrowth of field investigations on evaporation 

control begun by Mansfield (1953, 1955) in Melbourne, Australia, 

in 1952. Mansfield's work, in turn, was an application of theoretical 

considerations developed by Langmuir (1917), and later applied by 

Hedestrand (1924), Adam (1941, chap. 2), Langmuir and Langmuir (1927), Rideal (1925), Langmuir and Schaefer (1943), and 

others to the reduction of evaporation of water.

Certain classes of organic compounds, having a hydrophylic 

(water-attracting) portion and a hydrophobic (water-repelling) 

portion in their molecular structures, possess the property of being 

able to spread out on a water surface. The hydrophobic portion 

of the molecule consists of a hydrocarbon structure for this purpose, preferably, a long straight-chain structure of 10 or more 

carbon atoms. The hydrophylic portion is a functional group such 

as a hydroxyl, carbonyl, carboxyl, amine, amide, or nitrile group. 

Various hydrophylic groups, in combination with hydrophobic 

groups, known to form monomolecular films are given in the following list.

Hydrophylic groups forming monomolecular films

[Adam, 1941, p. 50]

Group Formula Oroup Formula 

Carboxylic acid-______ -COOH Urea (substituted) -NHCONH2

Hydroxyl.___________ OH (below transition

Amine (on alkaline NH2 temp.) 

water). Nitrile_____________ CN

Amide______.________ -CONH2 Ester..-..----------- -COOR

Methyl ketone________ -COCH3 Aldoxime.-..-.------ -CHNOH

Through a decrease in the free energy of the associated molecules 

in the solid or liquid state, caused by the greater attraction of the 

hydrophylic portion of the molecules for the underlying water than 

the interattraction of the molecules for each other, individual molecules of a compound will detach from a central source or reservoir 

of the material where placed on a clean water surface. The molecules will spread out radially until a barrier or shore line is reached. 

If enough material is exposed at the water surface, the molecules 

Avill continue to detach and spread out until they form a closely 

packed, or compressed film, one molecule thick, covering the entire 

reservoir surface. Such a film has been shown (Langmuir and 

Langmuir. 1927, Langmuir and Schaefer, 1943) to have the ability 

to retard the rate of evaporation of water.

The hydrophylic group used for the purpose of this application 

must be nontoxic. This criterion will essentially rule out most of 

the nitrogenous compounds given in the preceding list. The pres-
GEOLOGICAL SURVEY WATEB-STJPPLY PAPER 1480 PLATE 1

SCREENING APPARATUS AT SOUTHWEST RESEARCH INSTITUTE

Insulated trough contains battery jars used for testing various chemicals.
DISCUSSION OF THEORY

ence of calcium or magnesium ions in the water of the reservoir 

will essentially eliminate consideration of acids and esters; the acids 

will form the calcium or magnesium salts, which will no longer 

spread out to form or reform monomolecular films, and the esters 

will hydrolyze to give the same effects. This leaves the hydroxyl 

compounds, particularly the long straight-chain primary alkanols 

as the best materials to use. These straight-chain compounds, by 

nature of their chemical structure, will form the most effective evaporation-retardant film. (See fig. 1.) It will be noted that the

/

OH OH OH OH 

Uncompressed

A. Straight chain primary

00000000

HHHHHHHH

Compressed

OH OH 

Uncompressed

OH OH OH 

Compressed

B. Straight chain secondary

OH OH OH OH OH OH OH 

Uncompressed Compressed

C. Branched chain primary

OH OH OH OH OH 

Uncompressed Compressed

£>. Branched chain secondary

OH OH OH OH OH 

Uncompressed Compressed 

f. Tertiary

FIGURE 1. Effects of molecular structure on compressibility of films of alkanols.

straight-chain primary structure is capable of forming a more 

highly compressed film than the secondary, tertiary, or branchedchain compounds. The effect of branching has been intensively 

studied with the 17 isomeric methylstearic acids and other materials 

(Weitzel, Fretzdorff, and Heller, 1951a, b).

Calculation of the effect of a monomolecular film has been done 

in several ways. Basically, the effect of evaporation retardation 

is described as a resistance to evaporation (Langmuir and Schaefer, 

1943). If the evaporation of a clean, free water surface into a 

vacuum is taken as one resistance unit (Mansfield, 1956), the resistance of the laminar layer of water vapor and air immediately 

above the surface is about 600 units. If a perfect monomolecular 

film is taken as having a resistance to evaporation of 1,600 units,
6 EVAPORATION CONTROL RESEARCH, 1955-58

the total resistance is 2,200 units, and the reduction of evaporation 

would be 1,600/2,200 or 72.7 percent. Both wind velocity and relative humidity are critical factors, which vary widely, so that the 

rate of reduction of evaporation may vary from zero on a morning 

with 100 percent relative humidity to more than 90 percent on a 

hot, dry day with a steady wind blowing.

Anderson, Harbeck, and others (U. S. Geological Survey, 1954) 

were among those who developed the energy budget method of 

determining the rate of evaporation from a free water surface. 

This method consists of making an accounting of all incoming 

and outgoing energy; the difference is the energy utilized for evaporation. The application of an evaporation suppressant film does 

not affect the energy received as solar or atmospheric radiation. 

If evaporation is suppressed, the temperature of the water surface 

must rise until the energy, no longer being used for evaporation, 

is disposed of by other processes, such as back radiation and conduction, which will be described subsequently in detail. Thus 

after a calibration period needed to determine certain physical constants of a particular reservoir, the effectiveness of a film in suppressing evaporation can be evaluated and the resultant rise of 

water temperature computed. Temperature differentials of as much 

as 8°F have been observed between two adjacent steel stock tanks, 

each 10 feet in diameter, only one of which had a monomolecular 

film.

Important theoretical considerations are brought up by the method 

of application. Mansfield (1955) developed the I/A criterion, which 

is the ratio of length of exposed perimeter of solid particles of filmforming material to the area of exposed water surface to be covered. 

His calculations indicate a critical minimum I/A ratio of 2X10~3 

centimeter"1 (0.002 centimeter of perimeter per square centimeter of 

surface area) for film formation. This indicates that finely divided 

solid material is preferred to large lumps of material, if a solid is 

used as the film generator. The I/A ratio does not appear to hold for 

liquid materials. Likewise, the emulsion application procedure of 

Dressier (written communication, January 1958) either produces 

large exposed perimeter of material through formation of microparticles or is not governed strictly by the I/A ratio of Mansfield. Mansfield's I/A ratio indicates that 1 pound of flaked solid alkanol should 

be used for a maximum water surface area of 35,000 square feet.

The homologous straight chain fatty alkaiiols that are most readily 

available those having even numbers of carbon atoms suffer from 

a major disadvantage, despite their theoretical superiority, of being 

susceptible to biochemical oxidation. This oxidation not only takes 

place on the film after formation, but on the reserve supply if it is
LABORATORY INVESTIGATIONS 7

stored on the water surface. Similar straight-chain primary alkanols 

containing odd numbers of carbon atoms were not available during 

the course of this investigation.

A secondary problem, apparently common to all monomolecular 

evaporation retardant films, results from the film being swept off 

the reservoir and piled up on shore by the action of the wind.

LABORATORY INVESTIGATIONS

The laboratory work in this program was done in two stages. 

The first stage consisted of the laboratory screening of organic 

chemicals deemed to have some value as evaporation-retardant materials. Emphasis was placed on commercially available materials. 

Two preliminary specifications were that the molecular structure 

must have the basic chemical characteristics, and it must comprise 

a minimum of 10 carbon atoms. It was felt that any lesser number 

of carbon atoms in the straight chain would not only be too volatile, but would also provide a film too thin to be effective (Archer 

and La Mer, 1954).

The second phase of the laboratory work consisted of further 

evaluation, in stock tanks 10 feet in diameter, of those compounds 

or mixtures showing promise in the screening program.

LABORATORY SCREENING OF ORGANIC CHEMICALS

The screening apparatus used in the laboratory, for which technical construction details are given on page 41, is shown in figure 

2 and plate 1. As originally constructed, the apparatus held 

eighteen 9-inch battery jar test units. The apparatus was subsequently modified to accommodate only 14 units; the other space was 

occupied by a coil of copper tubing immersed in the insulated 

trough to bring the temperature of the air up to that of the water 

in the trough and test units as nearly as possible. Each test unit 

consisted of a battery jar 9 inches in diameter by 12 inches deep, 

fitted with a specially designed lid, an inlet for dry air, and an 

automatic feed reservoir containing distilled water to replace that 

evaporated by the air stream. The design of the lid was such that 

with a 14-inch clearance between the bottom of the lid cone and 

the water surface, the air velocity was constant across the entire 

surface area. A manometer was placed in the incoming air line 

and calibrated by means of a rotameter, in order to determine the 

rate of air flow.

Air, dried by passing over silica gel, was passed over the water 

surface at the rate of 12.5 liters of free air per minute. In the test 

units, the compounds to be tested were applied in solid or liquid
8 EVAPORATION CONTROL RESEARCH, 1955-58

11 9" diam x 12" battery jar

12-mm Pyrex tube 

-y2 " rubber tubing

5-mm vent

8-mm Pyrex tube

FIGURE 2. Details of screening apparatus.

form at a dosage equivalent to 1 pound per acre of water surface. 

This was a 5-milligram dose on the surface, 9 inches in diameter. 

Two jars containing untreated water were used as control units in 

each test bank. As the water in the jar evaporated, the water 

level was maintained by automatic replenishment with water from 

the reservoir. By starting at a predetermined level and refilling 

the reservoirs to this level, the amount of water evaporated could 

be easily determined. It was found necessary to replace the water
LABORATORY INVESTIGATIONS 9

in the feed reservoir every 24 hours. At a trough temperature 

of 30°C (86°F), the control units generally lost about 2.5 liters of 

water over a test period of approximately 110 hours of continuous 

operation. Such a test period gave results reproducible to within 

5 percent.

Materials screened and the results obtained are summarized in 

table 1. Materials rejected as evaporation retardants due to high 

water solubility are summarized in table 2.

Several samples of hexadecanol and other alkanols, several silicones, and other miscellaneous materials were not screened.

TABLE 1. Compounds screened as evaporation retardants

Sample 

No.

Test 

No. Composition Trade name

Saving in 

evaporation 

(percent)

Code No. of 

test

Primary alkanols (saturated)

1 

2 

3

13 

14

16

17

18 

84

91

15

19

110 

116

120 

81

82

83

4

5 

6 

7 

9 

11

87 

88

89

90 

8 

128

130 

134

135 

136

6

7 

8

9 

10

11

12

13 

15

16 

19

20

46 

81 

3 

4,42

5

17 

18,40 

19 

20 

21 

23

29 

31

32

33 

43 

66

68 

8

9 

11

.. do........... ........... ......

N.F.... ...........

cosmetic grade ..... 

fl-hexadecanol, 28 percent... __ ~

fl-hexadecanol, 52.5 percent .......

1 1-hexadecanol, 52.7 percent... ....

fl-hexadecanol, 34 percent ___

fCuCM Alkanols, 4 percent ____

fl-hexadecanol, 6 percent CH.__ ... 

\ 70 percent CM. . 

fl-dodecancl, 61 percent.. .......

fl-dodecanol, 55percent.. .......

fl-dodecanol, 71 percent.. ___

saturated coconut 

90 percent Ci2__ ... 

55 percent Ci2.. ... 

68 percent Cu.....

tl-dodecanol, 60 percent ____

\l-tetradecanol, 25 percent ..- _ ..- 

i 1-dodecanol, 71 percent.. .........

1 1-tetradecanol, 27 percent __ ..... 

fl-dodecanol, 80 percent.. ........

\l-tetradecanol, 19 percent ____

fl-dodccanol, 70 percent Cw- ------

f 1-dodecanol, 62 percent Cw... __

fl-hexadecanollRn ./, \l-octadecanol)80-50- ~

1-hexadecanol, N.F ....

1-hexadecanol, technical. 

Adol 52........ .....

Adol 54.. ......... .

}Adol63.. . ..........

}Adol65.. ........

JAdol 66.. ............ .

Lorol 24. -.- __ .

}Dytol E-46..... ....

Adol 62... ............

Adol 68.. . 

Cachalot, C-52..... ...

Jsiponol TX ___ . _ .

}siponol CX.......... .

}l>orol5. .... ... .....

}Lorol7 

JLorol 9 ________ _

Adol 10.. ...... ... ....

Adol 11.-.... ....

Adol 12..... ... ..

Adol 13... 

Adol 15..... .... ...

Adol 42.. ....... ... ...

}Dytol B-35. . . . ... ....

JDytol A 24..... ...

}DytolJ 68- 

Adol 14.. .............

90 percent cetyl alcohol.

jSiponol L2X. ......

\Siponol L5X. ... ...

Cetyl-stearyl mixture27.0 

23.0 

34

36.2 

22.0

54

19.2

37.8 

37.8

30 

68

37

44.6 

31

42 

21

56

18

54 

65 

15 

60 

None 

50

16 

19 

21

25 

28 

21.5

43 

None

60.5 

49

682-WE. 

Do. 

712-WE, No. 

15. 

682-WE. 

699-WE, No. 

43.

699-WE, No. 

55.

682-WE.

Do.

682-WE, No. 

52. 

699-WE, No. 

45. 

712-WE, No. 

38. 

699-WE, No. 

47. 

682-WE.

699-WE. 

Do. 

712-WE. 

Do.

Do.

Do. 

Do. 

Do. 

Do. 

Do. 

DC.

Do. 

Do.

Do.

Do. 

Do. 

Do.

Do.

721-WE.

Do. 

Do.
10 EVAPORATION CONTROL RESEARCH, 1955-58

TABLE 1. Compounds screened as evaporation retardants Continued

Sample

No.

Test

No. Composition Trade name

Saving in

evaporation

(percent)

Code No. of

test

Primary alkanols (saturated) Continued

142 

143

93 

142 

143

144 

85 

79

80 

84 

21

129 

145 

155 

157

12 

14

17 

24 

25 

26 

42 

48

49 

1,14 

26

67 

28

Hydroabietyl alkanol ______

1-octadecanol, industrial grade _

fl-docosanol .......................

fDimethyl octanol ________

\Trimethyl heptanol... ...........

Cetyl alcohol, N.F.,

Abitol...... ..... 

Cetyl alkanol, N.F....

Lorol 28....... . .

Adol60_.._ .._ ._

}Adol67_.._. .....-

Lorol24.._. ._._.._.

Fatty alkanol mixture.

Cetalol O. .............

3101-R-485-104R. .....

None 

1.3

10.8 

14.4 

56.2 

57.8 

55 

45

53 

144 

None

None 

52.2 (») 

2.3

721-WE. 

Do.

Do. 

Do. 

Do. 

Do. 

699-WE. 

Do.

Do. 

712-WE. 

Do.

Do. 

721-WE.

Primary alkanols (unsaturated)

11

115 

10 

20

86

17

6 

22 

24

61 19-octadecenoL. _ . ___ . .....

19, 12, 15-octadecatrienol . .... .

| Adol 42.. __.. .. .

Adol 80.. ...... .... ...

Adol 22.. .............

Unadol 90. ... ......

25

None 

7.5 

6

8

682-WE.

712-WE. 

Do. 

Do.

Do.

Secondary alkanols (saturated)

112

113

114

22

23

24

25

51

76

79

34

35

36

37

Methyl heptadecyl carbinol. ..... Methyl heptadecyl

Diheptadecyl carbinol.

34

None

1

15

1

699-WE.

Do.

Do.

712-WE.

Do.

Do.

Do.

Nitrites

62 59 699-WE.

Dihydroxy and polyhydroxy compounds

12

27 

28

18

68 

27

2, 5-dimethyl hexane-2, 5-dIol ..... 

3, 6-dimethyl-3, 6-octanediol. .. .

Adol 45.. __.-- . .

Dimethyl hexanediol.. 

Dimethyl octanedioL .

None

11 

16

682-WE.

699-WE. 

712-WE.

Ethylene oxide condensation products

121 

102

104

101 

103

28,41 

52

53

25 

26

Polyoxyethylated tallow alkanols. 

N, N-polyoxyethylene fatty acid 

amide, 5 mols ethylene oxide. 

Mono fatty acid ester of polyoxyethylene glycol.

Mono fatty acid ester of polyoxyethylene glycol, 2-mols ethylene 

oxide.

X-69._.._ ... ... ....

Ethomid HT/15.......

Ethofat 60/12..- ... -

Ethomeen 2 c/18.9 __

51 

18

15

None 

None

712-WE. 

Do.

Do.

715-WE. 

Do.

See footnotes at end of table.
LABORATORY INVESTIGATIONS 11

TABLE 1. Compounds screened as evaporation retardants Continued

Sample

No.

Test

No. Composition Trade name

Saving in

evaporation

(percent)

Code No. of

test

Ketonea

56

57

58

54

94

55

124

131

57

58

66

12

46

22

64

70

Methyl pentadecyl ketone ____

Anthraquinone ________ _

ketone.

ketone.

tone.

12

22

6

30

None

None

699- WE.

Do.

Do.

712-WE.

Do.

715-WE.

712-WE.

Do.

Siliconea

108

109

132

133

137

146

156

1

2

3

5

6

7

Methyl silicone __________

.....do... ___ . --_ 

.....do.. 

Silicone ______________

D-C 200 fluid, 100 cks a.

D-C 200 fluid, 1000 cks.

D-C 510 fluid...... 

D-C 550 fluid. ........

Silicone SF-96, 40 cks.

D-C 702 fluid...... 

Z-4141..... 

17.8

17.0

20.4

26.2

10.0

721-WE.

Do.

Do.

Do.

Do.

Do.

Phenols

111

105

106

107

13

55

56

19

3-2V-pentadecyl phenol ______

nol.

cinol. 

Cardolite 6463. 

14

20

None

20.1

712-WE.

Do.

Do.

Do.

Amines

59 

60 

65

66

61 

63 

64 

127 

125 

122 

126

67 

60 

9

11

6 

7 

8 

14 

28 

62 

65

Tertiary Ci8 Cj4 amines (mixture). 

Tertiary Cu Cu amines (mixture).

Stearyl-N-alkyl imidazoline. .....

Armeen DM-18.. 

N-coco morpholine. 

N-tallow morpholine 

Stearoguanamine _ .- 

Amine 8. _____ 

None 

None 

None

3

34 

None 

None 

None 

None 

6 

None

699-WE. 

Do. 

712-WE.

Do.

715-WE. 

Do. 

Do. 

Do. 

Do. 

712-WE. 

Do.

Acids

44 

39 

40 

41

45 

48 

32 

119 

96

98

29 

30 

36 

38 

92 

31

53 

70 

71 

72

73

74 

77 

80 

48

50

1 

2 

3 

4 

12 

151

Stearic acid single pressed.. ......

Hydrogenated marine fatty acid, 

No. 52. 

Hydrogenated tallow fatty acid, 

No. 57. 

Hydrogenated tallow fatty acid, 

No. 58.

Terephthalic acid... .... . .

Mixed Cio dicarboxylic acids. .... 

N, N-dioctadecyl carboxyamino 

acid. 

9 (10) monohydroxystearic acid. . .

Oleic acid... ___ . .............

Fatty acid No. 35 

Tallow fatty acid. . 

Oleic acid....... .................

Stearic acid single 

pressed. 

Hydrogenated marine 

fatty acid, No. 52. 

Hydrogenated tallow 

fatty acid, No. 57. 

Hydrogenated tallow 

fatty acid, No. 58. 

Neofat 18-55 

T.P.A., technical 

DiHTzwitterion. 

Monohydroxystearic 

acid. 

Emersol 210 elaine.. 

Emerscl 233 elaine _ .. 

Fatty acid No. 35. . 

Fatty acid No. 42... 

Sap. Or. red oil. .- 

None 

12 

12 

22

8 

None 

8 

11 

14

6.5

None 

None 

5 

3 

None 

None

699-WE. 

Do. 

Do. 

Do.

Do. 

Do. 

Do. 

Do.

712-WE.

Do.

715-WE. 

Do. 

Do. 

Do. 

Do. 

Do.

See footnotes at end of table.
12 EVAPORATION CONTROL RESEARCH, 1955-58

TABLE 1. Compounds screened as evaporation retardants Continued

Sample

No.

Test

No. Composition Trade name

Saving in

evaporation

(percent)

Code No. of

test

Acids Continued

33 

34 

35 

37 

42 

46

47

16 

17 

19 

20 

21 

57

58

Fatty acid No. 86.... .............

Pulverized limestone, coated

Pulverized limestone, coated

Fatty acid SD........

Fatty acid No. 20... ~ 

FattyacidNo. 25... -

Fatty acid No. 36..... 

Fatty acid No. 86 .... 

Pulverized limestone, 

RP-1.. .............

Pulverized limestone, 

R-2._ ...............

None 

6 

None 

14 

None

6 

None

715-WE. 

Do. 

Do. 

Do. 

Do.

712- WE. 

Do.

Amides

50 

51

52 

53 

97 

123

61 

63

62 

65 

49 

63

fPalmitamide, 22 percent.. ........ } Armid HT.. -..- .-

Armid 16... . ..........

Armid 18 ...........

N-tertoctyl acrylamide

None 

None

None 

None 

None 

None

699- WE. 

Do.

Do. 

Do. 

712-WE. 

Do.

Esters

ftQ

49

117

118

75

77

76

56

75

7

8

10

23

59

Cetyl palmltate (technical). ......

Sperm oil... ......................

DMT..-_ .............

Methly tallowate.....

Moby Dick Sperm 90.

Moby Dick N.W. 45°.

9

None

None

None

39

16

699-WE.

Do.

712-WE.

Do.

715-WE.

Do.

712-WE.

Miscellaneous

78

95 

99

70

71

100 

72

73

74

138

139

140

141

44

47 

51

9

11

24 

10

15

16

20

21

22

23

N-octadecyl maleic anhydride, 

product condensation.

Trimethyl - N - alkyltrimethylene 

dlamine distearate.

HT-maleamic acid .... 

2 HT methyl stearate..

Ethoduomeen T/13 

distearate.

Resoflex 296 __ .......

Tnanl 14

Tagol 40

Tagol65 ............

10

23

18

None

11 

None

14.1

4.8

24.1

32.5

5.6

712-WE.

Do. 

Do.

715-WE.

Do.

Do. 

721-WE.

Do.

Do.

Do.

Do.

Do.

Do.

1 This value is pro rata. The film broke up and lost its effectiveness at different times in a duplicate 

set of reruns. At the time this value was determined, both tests were nearly identical. Elapsed time 

about 70 hours. Average value at end of test (114 hours) 27 percent.

8 Test conducted on 10-foot tanks only.

a Cks, centistoke.

TABLE 2. Compounds rejected as evaporation retardants

Sample

No.

26

- 7

68

Composition

Polyvinyl alcohol

resin.

Dodecyl diethylene 

triamine.

Polyethoxylated vegetable oil.

Trade name

Vinol FH 600..

Amine ODT_.

Emulphor 

El-719.

Lot or

serial No.

2834.. ..

55-11-178-

None _ ..

Appearance

White powder.. ...

Viscous tan liquid 

amine odor.

Oily, yellow 

liquid.

Reasons for rejection

Did not form a film;

sank to bottom of

beaker and dissolved

slowly.

Dispersed, formed turbid, translucent mixture.

Dissolved completely 

miscible with water.
LABORATORY INVESTIGATIONS 13 

FIELD SCREENING, USING 10-FOOT TANKS

Two corrugated stock-watering tanks, 10 feet in diameter and 

2 feet deep, were buried in the ground to within 2-3 inches of the 

top. Each tank was fitted with a brass stilling well set on a notched 

glass plate. The test area was fenced off with 1-inch mesh chicken 

wire. In operation, the tanks were thoroughly cleaned, using acetone when necessary, and flushed and filled with clean water. The 

material to be tested was applied by one of several methods to the 

surface of one tank; the other tank was used as a control. Evaporation was allowed to proceed under natural conditions until the 

film-forming material gave no further positive evaporation reduction effect as determined by inspection of the data obtained daily.

Generally, solid material was applied by means of a small cage 

raft floating on the surface and held in place by a string or wire 

stretched taut across the top of the tank. Buoyancy was maintained by large corks or cork rings. Liquid materials were either 

applied all at once, in somewhat lesser quantities than the solid 

compounds, or were applied slowly by gravity feed through a 

capillary tube.

Recorded data included the level of the water, as determined by 

an average of three readings of the hook gauge in the stilling 

well in each tank, the surface temperature of the water in each 

tank, the air temperature, the wind velocity and direction, and the 

wet-bulb temperature. These data were obtained in the morning 

and evening during the week, and once a day on Saturday and 

Sunday. From them, the rate of evaporation under the prevailing 

conditions was easily determined as was the percent reduction of 

evaporation.

Test results using the 10-foot tanks are summarized in table 3. 

It will be noted that until some bacteriostatic agent was utilized, 

the film life was very short. This indicated that the problem of 

biochemical oxidation was one to be reckoned with, contrary to 

preliminary experience in Australia. Other conclusions drawn from 

this phase of the work were:

1. Even in cool weather, a dry "norther" will cause considerable 

evaporation. This indicates that the use of the monofilm technique is, under certain circumstances, advisable the year round.

2. A compressed film will assist in keeping a reservoir from freezing over. Examination of the energy budget theory confirms 

this experimentally determined phenomenon; the extra energy 

not consumed in evaporation must be withdrawn from the reservoir before freezing can occur.

550194 O 
14 EVAPORATION CONTROL RESEARCH, 1955-58 

TABLE 3. Results of tests in 10-foot tanks

Test 

No.

1 

2

3

4 

5

6

7 

8

9

10

11 

12

13

14

Evaporation 

retardant

Hexadecanol 

(Fisher).

62).

11). 

X-69 (tallow alkanol-ethylene 

oxide condensation product; 

American 

Alcolac)

62). 

.... do.. __.._.____

Hexadecanol 

(Adol 54).

(mixed brands).

(Cetalol O).

(Lorol24).

Hexadecanol 

(Siponol CX) in 

dodecanol 

(Lorol 7), 15 

percent by 

weight. 

. ---.do... _________

___.do ____________

Methyl 

heptadecyl 

carbinol.

Amount 

used (g)

1.8 

1.8

1 ft

1.8 

1.8

108.6

113.4 

50

50

Kf\

54 

122

7

50

Length 

of test 

(days)

7 

11

7

13+

10

g

47 

64

35

61

19 

27

8

7

Type of application

0.8 g, broadcast; 1.0 

g, in raft (aluminum screen) .

 .do -.-

0.8 g, broadcast; 1.0 

g, in raft (aluminum screen) .

... ..do. .------....

screen).

Raft (copperbronze screen).

.....do.. -------

--...do --------

--..do .. -- 

Liquid phase, 

dripper.

 .do.....- --..

 .do.... - 

Raft, copper screen. .

Reduction of 

evaporation 

(percent)

25.9 

24.9

4.3

None 

15.4

11.8

33.0 

16.7

35.0

25.7

30.8 

25.6

28.0

17.7

Remarks

Amount equivalent to 

1 Ib per acre broadcast, and 1.2 Ib per 

acre in reserve supply.

Material broadcast; 

added as a melt.

Larger raft used; film

generation from raft 

only. 

11.2 g cupric sulfate 

pentahydrate, 

CuSO4 -5HjO (=0.6 

ppm Cu) added to 

water. 

Hexadecanol compounded with 1 

percent cupric 

stearate. 

Hexadecanol compounded with 1 

percent "G-4 Dichlorophene" 

(Sindar).

pounded with 5 percent "Chlorhydrol" 

Alj(OH) 5 Clx, 

Reheis Co., a 50 

percent by weight 

aqueous solution. 

Applied from canister 

dripper, with 0.0135- 

in. drip hole in 

bottom.

Canister dripper,

0.019-in. I.D. stainless steel drip tube 

in bottom. See 

under No. 11 also.

0.020-in. brass plate, 

with 0.0135-in. hole, 

in bottom. See 

under No. 11 also.

1 74 hours.

3. Rain will break up the film; it will re-form promptly, however, 

if adequate material reserves are present.

4. During periods of high humidity, the saving in evaporation was 

small. Thus in humid areas, the use of a film would probably not 

be economical, but in such areas the loss by evaporation is generally of little consequence.
LABORATORY INVESTIGATIONS 15

5. Any compound not giving excellent results in the laboratory 

screening phase was of little value in this phase of the program.

MISCELLANEOUS LABORATORY STUDIES 

BACTERICIDAL AND RACTERIO STATIC ADDITIVES

The results on the first few tests in the 10-foot tanks indicated 

that some destruction of the film was taking place, or some 

other phenomenon was occurring that caused the effective life of 

the film to be shortened. When 0.6 ppm (parts per million) 

copper as cupric sulfate pentahydrate (CuSO* . 5H2O) was added 

to the water in the tanks, the effective life of the film increased 

markedly (test 7). This emphasized the necessity for inclusion of 

some bacteriostatic or bactericidal material either in the water or 

in the film itself. The former alternative was promptly ruled out, 

on both cost and safety considerations. To bring Lake Mead, for 

example, to a concentration of 1 ppm of copper would require 

approximately 160,000 tons of copper sulfate pentahydrate, and 

there is no assurance that distribution would be sufficiently uniform 

to eliminate the possibility that the water might be poisonous in 

some areas. Inclusion of the bacteriostat in the film appeared to 

be much more promising. Copper salts of several organic acids 

were prepared, several other acids were collected for preparation 

of copper salts, and samples of a few cosmetic bacteriocides not 

containing copper was also obtained for testing.

The copper salts were compounded with hexadecanol or octadecanol by melting and cooling with stirring. Generally, 1 percent 

by weight of the copper salt was incorporated into the alkanol. 

The solubility of the copper salts in the hexadecanol depended upon 

the acid structure. The various copper salts and their relative solubility in hexadecanol and other bacteriostatic materials used in this 

pase of the investigation are shown in the following lists.

Solubility of various copper salt bactericides in hexadecanol

Solubility in molten 

Copper salt hexadecanol

Isosebacate._--_________________-____-__--_-_- Fairly good.

12-hydroxystearate____-_-___-______-__--_---__ Very good.

Gluconate___________________________________ Very poor.

Benzoate-____________________________________ Poor.

Salicylate---_____-_-_--_-_____-____-._-_-_--__- Fairly good.

Succinate_ ______-___-_---______-_--__-________ Do.

Tartrate____________________________________ Extremely poor.

Stearate______________________________________ Very good.

Laurate______________________________________ Do.
16 EVAPORATION CONTROL RESEARCH, 1955-58

Formula 

H2 S C COOH

Compounds used as bacteriocides or bacteriocide intermediates

Name 

Aminophenylmercaptoacetic acid.._.__.__________...-_--__-.- H2N

Hydrogenated bisphenol A._..____..._._._____. ___........... HO

Phenylmercaptoacetic acid.

OH

H2 -S C COOH

Sesame oil USP.....-...._._.._______________________ _____.......___......____-........-..___.--

Thiodiglycolicacid........................................... HOOCCHa S CH2COOH

Thiomalic acid.. ................................ ......... HOOC GHz- CH(SH)COOH

Q-4 Dichlorophene.

G-ll Hexachlorophene.

Monothioglyeerol (Thiovanol)..__............................ HOCHjCHOH CH2SH

Chlorhydrol (aluminum chlorohydroxide complex)............ Ah(OH)iClx

The copper salts of the various acids were prepared by dissolving 

a slight excess of copper sulfate pentahydrate (CuSO4 -5H2O) in hot 

distilled water, and adding the acid in the desired amount. The mixture was stirred vigorously, while concentrated ammonium hydroxide 

(28 percent NH3 ) was cautiously added. If the acid was a solid, it 

was generally melted, if possible, in the hot copper sulfate solution 

before adding the ammonia. This promoted a faster and more complete reaction. The addition of ammonia was continued until a slight 

excess was present as indicated by the formation of the deep blue 

cuprammonium complex. The mixture was then allowed to cool. 

The precipitated copper salt was filtered off, washed free of the 

cuprammonium complex, and air dried.

During the large-scale field tests, it was found that copper stearate 

tended to undergo ion exchange to calcium stearate. This latter salt 

formed a hard crust on the surface of the particles of hexadecanol 

and interfered with the formation of the film. Copper laurate appeared to be much better from this standpoint than copper stearate; 

however, the rate of formation of a film from hexadecanol compounded with copper salts of fatty acids was not entirely satisfactory. 

Other bactericides tested in the 10-foot tanks were G-4 Dichlorophene, and Chlorhydrol, an aluminum chlorohydroxide complex, 

A12 (OH) 5C1X .
LABORATORY INVESTIGATIONS 17

WIND STUDIES

The effects of wind on the film constituted a recurring problem. 

Although the effect of wind on the test films in the 10-foot tanks 

was minor, preliminary calculations indicated that on a large 

reservoir (several square miles or more), wind effects could cause 

a prohibitively large consumption of evaporation retardant.

In order to make a preliminary study of the effects of wind, a 

plywood superstructure was constructed for the thermostat trough 

of the screening apparatus. Sliding plastic windows were placed 

at about 2-foot intervals along the side of the cover. Both ends 

were left open. The trough was filled as nearly as possible to the 

brim; the plywood cover and the water surface thus formed a wind 

tunnel. A sketch of the cover is given in figure 3. By inserting

*/2" plywood top

V plywood sides 

I"x2" cleat

5"x 5" plastic sliding windows

nsulated trough

FIGURE 3. Apparatus used for determining effects of wind on a monofilm.

an anemometer through the windows, the air velocity at the particular area in the tunnel could be measured. The windows also 

permitted observation of the spreading behavior of the film. A 

12-inch electric fan, connected to a variable transformer and placed 

at one end of the apparatus, furnished a 10 mph wind easily. 

Wind velocities above this caused wave motion which resulted in 

some of the water in the trough splashing out at the downwind 

end.

Tests were made by placing a supply of hexadecanol at either the 

downwind or upwind end of the tunnel, and timing the rate of
18 EVAPORATION CONTROL RESEARCH, 1955-58

spreading as observed through the windows. Usually, the front 

of the newly-formed film was discernible from the presence of 

small particles of hexadecanol, or by a difference in the reflection of 

light from the surface. Although this procedure is highly subjective, it was possible to draw two general conclusions from the 

tests run:

1. Although some upwind spreading was noticed against a 10-mph 

wind, it was so slow as to be impractical. It is doubtful that 

complete coverage would be obtained from the downwind shore 

alone on any reservoir with a surface area of more than 1 acre.

2. The film is piled up downwind when the hexadecanol is applied 

at the upwind end. Recovery, on a small scale, is rapid, however. On a large scale, some recovery can be expected; shore 

losses will, however, use up some of the material.

No attempt was made to vary the wind velocities, for winds of 

10 mph or more are common in Texas, and it was assumed that a 

wind of less velocity would offer less resistance to the spreading 

of the film.

LIQUID-PHASE APPLICATION METHODS

Work on evaporation control by the East Africa High Commission on an 88-acre reservoir near Nairobi, Kenya, British East 

Africa, utilized the application of hexadecanol in "illuminating 

paraffin," or kerosene (Grundy, 1957). The use of kerosene or 

any other flammable solvent, for that matter on practically any 

reservoir in the United States would be undesirable, if not actually 

forbidden. Since liquid phase application of the evaporation retardants is attended by several advantages over solid phase application, methods of applying liquid materials were studied.

The liquid materials investigated included 15 percent hexadecanol 

in commercial dodecanol, commercial dodecanols, and commercial 

dodecanol in ethanol. The dodecanols used generally contained 15- 

30 percent of the Cie and Ci8 homologs in their composition. 

Lorol 7, Siponol L5X, and Adols 10, 11, and 13 were the principal 

materials used. All of these, in themselves, showed at least 50 

percent reduction of evaporation in the screening program. Ethanol 

was used to lower the cloud point of the commercial dodecanols 

so that they could still be applied in the liquid phase in cool 

weather.

Canisters 3 inches in diameter and 10 inches high were used in 

the initial tests. Holes were drilled in the bottoms of several 

such cans, and the rate of flow measured. Holes three sixty-fourths
LABORATORY INVESTIGATIONS 19

and one thirty-second inch in diameter were found to be so large 

as to permit the liquid material to flow in a steady stream. 

A hole 0.0135-inch in diameter produced a satisfactory flow rate.

Tests were made on these canisters, and on several other dripper 

applicators described below, on the 10-foot tanks. The dripper 

was filled with the liquid and fastened to a rod or stake with a 

ring clamp. The liquid was allowed to drip onto the water surface. 

The same kind of data described on page 13 for 10-foot tank 

tests was obtained. In addition, the dripper was weighed dally to 

determine the weight loss (amount of liquid applied to the water 

surface).

Other drippers with the following modifications were made:

A stainless steel tube, 6 inches long and with an inside diameter 

of 0.019 inch, was soldered into the bottom of a canister. The 

tube was extended !/2 incn into the can above the bottom in order 

to prevent clogging by particles of foreign matter. This dripper 

proved to be quite fragile, and the tube was knocked loose several 

times, despite considerable care in handling.

The bottom of a canister was cut out and replaced by a 0.020- 

inch brass plate having a 0.013-inch hole drilled in the center. 

The hole plugged quickly, because particles of foreign matter were 

inadvertently introduced in handling and refilling.

Performance data on the above applicators are included in table 

3.

CLOUD-POINT DETERMINATIONS

In making the liquid-phase application tests, it was noted that 

the liquid dodecanol often solidified in the canister and drip tube 

or hole. Solidification occurred generally at about 20° C, or 68° F. 

As it was felt desirable to continue application at temperatures 

below 68° F, means of lowering the cloud point or freezing point 

of the material were studied. Several solvents were utilized for 

this purpose. The cloud points of the pure commercial dodecanols 

and mixtures of these with petroleum ether, Freon 11, and ethanol 

were determined by Official Method Cc 6-25, of the American Oil 

Chemists' Society. Results are summarized in the table on page 20. 

The variations of the cloud points of ethanol-dodecanol and hexadecanol-dodecanol mixtures are plotted in figures 4-6.

The government regulations pertaining to the use of ethanol 

would present problems although it is possible that a dodecanolethanol mixture may be considered to be a specially denatured 

formula for use as an evaporation retardant.
20 EVAPORATION CONTROL RESEARCH, 1955-58

Cloud points of dodecanol, hexadecanol, and solvent mixtures

Composition

Lorol 11........

Siponol CX....

Lorol 11 

Siponol CX....

Siponol CX....

Siponol CX....

Percent

100

100

100

30

70

en

50

70

30

90

20

80

30

70

40

60

en

50

60

40

70

30

on

20

10

Cloud 

point, °F

69.8

68.0

} 75.0

} 89.6

} 105. 8

} 73.4

} 87.0

} 93.2

} 96.5

} 102.2

} 109.0

} 113.

} 116.6

Composition

Ethanol ........

Ethanol ........

Adol 11. .......

Ethanol ........

Lorol 11... __ .

Adol 10- .......

Percent

5

95

10

90

15

85

20

80

25

75

30

70

35

65

40

60

45

55

50

50

100

15

85

15

85

15

85

Cloud 

point, °F

1 62.5

1> 53. 6

} 50.0

46. 4

} 43.0

} 42.8

37.4

} 35.6

oo. o

} 32.0

66.0

} 41.1

} 39.2

Composition

Adol 10 ........

Siponol L5X ...

Ethanol ___ .

Siponol L5X...

Freon-11 .......

Freon-11.......

Adol 10.. ......

Freon-11.......

Siponol CX ....

Freon-11.. __ .

Siponol CX _ .

Freon-11.. .....

Adol 11.........

Evaportrol .....

Petroleum

Ether.... ....

Lorol 11 - 

Petroleum

Ether ........

Lorol 11........

Petroleum

Ether -- 

Petroleum

Ether.. __ ..

Percent

100

100

15

85

20

80

15

85

5

95

120

180

15

85

100

5

95

10

90

5

95

10

90

Cloud 

point°F

59.0

66.3

O*7. U

} 50.0

} 42.0

} 118.4

\ 102.2

1

107.6

} 61.0

1 /»n

i Approximately. 

50

40

30 \

\

20

10

8 12 

TEMPERATURE, IN DEGREES CENTIGRADE

16 20

FIGURE 4. Cloud-point temperatures for various ethanol-dodecanol (Lorol 7) mixtures.
LABORATORY INVESTIGATIONS 21

90

80

70

60

50

40

30

20

10

z

20 30 40 50 

TEMPERATURE, IN DEGREES CENTIGRADE

FIGUEE 5. Cloud-point temperatures for various hexadecanol (Siponol CX)- 

dodecanol (Lorol 7) mixtures.

WICK-DISPENSER TESTS

Wicks were considered as an inexpensive and simple method of 

controlling the rate of application of a liquid evaporation retardant. 

Tests were made on various natural and synthetic fibers as potential wick materials. For preliminary tests, a hole was punched 

in the bottom of a 6-ounce can with a 4d nail, and the necessary 

twine drawn through the hole with another strand of twine. (See 

fig. 7) The doubled ends were cut to make single strands extending 

below the bottom of the can. The rates of flow for various intervals 

were then determined.

It was found that the drip rate decreased abruptly after 24r-72 

hours. At first, this slow-down was attributed to swelling of the 

wick fibers by the dodecanol. This is no doubt still part of the 

trouble. It was noted, however, that the cans tended to rust 

around the wick hole. Thus, the rust was also a factor in the
22 EVAPORATION CONTROL RESEARCH, 1955-58

»u

80

i t i t

i 70 

O

z 

x 60

d

| 50

hz

LU A .

o 40

QL 

LJ

£L

30 

20

/

/

/

/

/

/

/

/

20 30 40 50 

TEMPERATURE, IN DEGREES CENTIGRADE

FIGURE 6. Cloud-point temperatures for various hexadeconal (Siponol CX)- 

dodecanol (Lorol 11) mixtures.

decrease of the drip rate. In an effort to combat this corrosion, 

a small piece of ^-inch (outside diameter) copper tubing was 

soldered to the bottom of the can, and the wick pulled through 

the tubing.

In searching for a cause of the rust, it was found that the dodecanols used (Lorol 7 and Siponol L5X) were hygroscopic. Moisture analysis on two samples of these materials that had been 

exposed to the atmosphere for a period of 4-6 weeks indicated a 

moisture content of about 0.2 percent. A sample of Lorol 7 withdrawn from a fresh, factory-sealed drum was found to be anhydrous. Subsequent analysis of this material after approximately 

2 weeks in the open indicated a moisture content of 0.1 percent. 

Such moisture would undoubtedly cause a "tin can" to rust, even 

though slowly.

The combination of the hygroscopic nature of the dodecanol and 

the swelling characteristics of the wick fibers essentially ruled out 

the extended use of the simple "tin-can" wick, dripper for this 

program. The use of this dripper may possibly be practical in
LABORATORY INVESTIGATIONS 23

extreme cases. Figure 7-9 are illustrated directions for the use 

of this type applicator.

~~- Paint bucket, or simitar 

covering, to keep rain, 

dust and bugs out

Cut loops

FIGURE 7. How to make an evaporation retarder.

FT

Mount either way 

\

Place as close to high-water level as 

possible without string touching 

water

FIGURE 8. Sectional view showing method of installing dripper.
24 EVAPORATION CONTROL RESEARCH, 1955-58

"1

~ | Thermometer

o

FIGURE 9. Sketch showing arrangement of instruments.

A summary of the data is presented in the table on page 25. Most 

of the tests were made at temperatures of 70° to 75° F. Flow 

rates versus time for various wick materials are plotted in figures 

10-12.

.24

IX.

1 .20

|.16

tr 

o

? .12

.08

.04

 00

34567 

TIME, IN DAYS

10 11

FIGURE 10. Variation of flow rate of dodecanol with time, using orlon wick (test No. 8).
LABORATORY INVESTIGATIONS 25

L5X) through wick materials dodecanol (Siponol various of Flow rates 

F] 70°5 [In hour attograms per

of flow Rate 

December

November

CO 

CN

os

00

CO

CN

CO

*

IN

.

i

.

CN

S

II

Wick material

ll

S

CO

i

o

1

IO

o oooo 

o 

If

c>

1 I

§

S 

§

CO

o

1o

10

o S2oo?5

1O i1O 1-1

"4< COC^COO-*-*!

1-H O> 1-H I ( CO CM ra

I i ! 

oo'"«^i^S'

O

X)

en QQ CO tfi

HI <PHpM

QO O> O >-H N CO -^ U3 ?O t*

!

£

Fiberglass 

3

flow of Ratei

*

CO

<*"

CO

o

0,

00

-

ro

||

material Wick 

u

GGGGGS'*' *" '"'

iiisiiiiis O <*"r-IC<5

lllllillll

O Tl< i-i *H OJ

**

IHII

rt

o i-i >ri I-H CN

o

J 'coco

-^ocoggg^gFiberglass string 

(loose)... Fiberglass Nylon (string) Asbestosglass tube).-.. Cotton (in plastic bottle) Cotton(in ...

tubing) Oron ^-inch (ncopper tubing). W-inchCotton (in copper .- 

tubing) (iNylon copper 

(in tubing) Nylon capillary 

aasassast*

from heating Braided fiberglass tapeies. the 6 oflaboratory. lowering repeated owingtoemperature Observations 1 a

wool. * Twisted glass fibersrom Two 2ply. 

7 Terminated. »Three ply. 

No. tightly than 20. test packed Test unbraided. No. 16Loose fiberglass, 4 more was
26 EVAPORATION CONTROL RESEARCH, 1955-58

10 11

TIME, IN DAYS

FIGURE 11. Variation of flow rate of dodecanol with time, using orlon wick in copper

tubing (test No. 25).

567 

TIME, IN DAYS

10 11

FIGURE 12. Variation of flow rate of dodecanol with time, using nylon wick in copper

tubing (test No. 27).
LABORATORY INVESTIGATIONS 27

PELLETING OF SOLID EVAPORATION RETARDANTS

In the large-scale field test, described on page 30, it was noted 

that there was considerable loss of solid material by attrition and 

abrasion of the flakes in the generating rafts. A short study of 

methods of getting small, hard pellets of material was therefore 

undertaken. Mansfield (1956) described a procedure used in Australia in which molten hexadecanol was passed upward through a 

perforated plate into hot water. The water in a tall tank was 

cooled at the top, and the beads of organic material thus solidified 

as they passed upward through the water. The water was overflowed slowly and the pellets were caught in a sieve.

Attempts to pelletize the flake material in a tablet machine of 

the type used in the pharmaceutical industry were unsuccessful. 

Extrusion of material heated to about 35°-40° C was somewhat 

more promising, although the strength of the particles produced was 

lower than desired.

Material which had been melted, cast into blocks, ground, and 

screened to pass a 14-inch mesh and be retained on a No. 10 mesh 

was found to be fairly satisfactory, although a particle size passing 

a No. 6 mesh and retained on a No. 14 mesh would have been 

better from the I/A ratio criterion. This method was used for 

the hexadecanols and octadecanols that were utilized in most of

Effect of concentration of polyethylene on the evaporation-retarding efficiency of

\-hexadecanol

[After Michaels, 1957]

Surface treatment

1-Hexadecanol:

polyethylene

polyethylene

cent polyethylene.

1-Hexadecanol:

polyethylene.

polyethylene.

cent polyethylene.

Particle of size 

treating agent

__ do.. _ ___

- do..........

 ..do .....

granules. 

 . .do..... 

 do. ...

 do. 

Initial 

water 

(grams)

985

985

880

837

883

867

822

873

782

822

839

Final 

water 

(grams)

247

247

609

610

610

312

192

691

608

602

625

Time 

of test 

(hours)

69

69

69

69

69

69

41.5

41.5

41.5

41.5

41.5

Average 

evaporation rate 

(g per hr 

per sq ft)

44.0

16.1

13.5

16.3

33.1

62.5

18.1

17.3

21.8

21.2

Reduction evaporation 

(percent)

0.0

63.2

69.4

63.0

24.8

0.0

71.0

72.5

65.0

66.0

Remarks

0.0515±0.0006 g

of additive on

surface; surface 

area 35 in^ (21

Ib per acre).

0.0500±0.0009 g 

of additive on

surface 35 sq in.

Ib per acre).
28 EVAPORATION CONTROL RESEARCH, 1955-58

the large-scale field trials. A pellet about the size of prilled ammonium nitrate a sphere or spheroid about 2 millimeters in diameter is the most desirable form of the solid evaporation retardants. 

Michaels (written communication, June 7, 1957) described the 

incorporation of polyethylene into hexadecanol (Lorol 24). He 

tested his materials in photographic trays, set in the draft of a 

hood. Four tests and one untreated pan for a control test were 

run. His results are summarized in the table on page 27.

RAFT DESIGN

The first several large-scale field tests made in this investigation 

were carried out using hexadecanol or octadecanol in rafts 2 feet 

square, made of 2 x 4 lumber, heavily varnished, put together in the 

form of an H, and covered with window screen. Aluminum and galvanized screening were found to be completely unsuitable, the former 

due to fouling by algae, the latter by both fouling and corrosion. 

Copper bronze and Saran screens were found generally satisfactory. 

It was necessary to hold the screen in place with wooden molding 

strips fastened with brass screws, as staples and nails corroded quickly. 

The rafts were constructed with the 4-inch side of the lumber parallel 

to the water surface, so that the raft rode very low in the water. As a 

result, there was a loss of hexadecanol by attrition against the top 

of the raft during periods of rough water caused by winds. Sketches 

of various types of rafts are presented in figure 13.

CONSIDERATIONS OF TOXICITY

The toxicological aspects of several of the materials under consideration have been mentioned on page 4. As it is desired to utilize these 

materials on any type of reservoir, including those which may serve as 

public water supplies, it is imperative that any material or combination of materials be nontoxic to man, farm animals, fish, and wildlife. 

Further, the aquatic balance of the reservoir should be affected as 

little as possible, if at all.

The Eobert A. Taft Sanitary Engineering Center, of the U. S. 

Public Health Service, Cincinnati, Ohio, has issued a comprehensive 

statement of clearance, from a consideration of the toxicity of 1- 

hexadecanol conforming to USP or NF specifications. The Public 

Health Service, also, has specifically withheld clearance for dodecanol, and by inference, any other composition of matter other 

than USP or NF hexadecanol. Copies of these statements are 

given at the end of this report.
LABORATORY INVESTIGATIONS

Float Float

Screen

Fill plug ///r~Solid top

 f/

//- Float

^^/J

1

Australia No. 1 Fiberglass

Screen

Float

Australia No. 2 Wood; 

adjustable plastic floats

Float

Screen

Circular metal design

H-frame, SwRI experimental

Closed or open top

Tower reservoir, proposed by SwRI for a 35-acre lake, 

near Seadrift, Tex. Legs are anchored in the 

bottom of the lake. Screen extends below waterline

FIGURE 13. Miscellaneous raft designs.

550194 O 60 3
30 EVAPORATION CONTROL RESEARCH, 1955-58 

LARGE-SCALE FIELD TESTS

The evaluation of different chemicals as evaporation suppressants 

is relatively simple in the laboratory. Under carefully controlled 

conditions reliable results can be obtained with one or more containers of untreated water for control purposes. Although laboratory tests are invaluable for comparing the relative effectiveness 

of different chemicals, the results obtained are perhaps the most 

favorable possible; and it is unlikely that water savings under 

natural conditions will be as large.

An out-of-doors test using containers as large as possible would 

be desirable; but, as the cost of metal tanks rises sharply with increased diameter, it is not economically feasible to use tanks large 

enough to simulate conditions found in natural ponds or reservoirs. 

The metal tanks used in the tests previously described had a 

diameter of 10 feet. One was left untreated and used as the control. It was thereby assumed that the natural evaporation from 

the two pans, if both were untreated, would be the same. A pretreatment test indicated this to be true. Although the 10-foot 

diameter tanks were large enough to permit making determination 

of the spreading velocity of a monomolecular film, they were not 

large enough for the wind to generate waves of any significant 

height. Field tests on natural ponds were thus considered necessary.

The use of ponds and reservoirs to test the effectiveness of a 

monomolecular film in suppressing evaporation introduces certain 

problems. Although it would be possible to construct two identically shaped ponds, there is no assurance that other physical 

characteristics would be identical. Seepage losses or gains would 

not necessarily be the same; even if the seepage rates were the 

same at one time, there is no assurance that they would remain 

the same over an extended period of time. Lining the ponds is 

not necessarily a panacea. Concrete-lined tanks are expensive and 

are not necessarily leak-proof. Plastic linings would be cheaper 

but are susceptible to mechanical damage. If a tank began to 

leak during a test, the results would be erroneous; but what is 

more serious is the possibility that the leak might not be detected.

One way to take into account the inherent differences between 

two natural ponds is simply to duplicate the experiment using first 

one ponds and then the other as the control. Two disadvantages 

of this scheme are the length of time required for the experiment 

is doubled, and the difficulty of being certain that all the filmforming material has been removed from the treated reservoir at
LARGE-SCALE FIELD TESTS 31

the conclusion of the first half of the experiment. Although it 

might be impossible to find any evidence of hexadecanol on the 

surface of the previously treated reservoir, some material may have 

been cast on shore and could possibly return to the water surface 

if the stage rose.

Some investigators have relied on data obtained from evaporation pan or evaporimeters to evaluate the reduction in evaporation. 

The usual technique is to plot pan evaporation against change in 

reservoir stage during a pretreatment calibration period. The slope 

of the line is the pan coefficient, and the intercept is the reservoir 

seepage loss or gain. The basic assumption is that the pan coefficient and seepage rate determined during the calibration period 

are applicable after the reservoir is treated. The validity of the 

pan coefficient theory is not unquestioned. Kohler, Nordenson, 

and Fox (1955) stated "It is not clear by what reasoning process 

it was conceived that lake evaporation should be proportional to 

that observed in a nearby pan, and there is little to be gained by 

speculation at this time."

The assumption that the pan coefficient during the treatment 

period is the same as during the calibration period is questionable. 

The Lake Hefner studies (Kohler, 1954; 1952) indicated that the 

monthly pan coefficient ranged from 0.13 to 1.32 for the class-A pan, 

and from 0.22 to 1.56 for the BPI (sunken) pan. For a small, 

shallow pond, the monthly variation in pan coefficient presumably 

would be less than for Lake Hefner, but the assumption that there 

is no month-to-month variation is not acceptable.

The second assumption, that the seepage rate during the calibration period is the same as during the treatment period, is 

acceptable provided the reservoir stage is the same during the two 

periods. Culler (oral communication) found that seepage losses 

from stock-water reservoirs in the upper Cheyenne River basin in 

Wyoming increased with stage, as it might be expected.

Because of the unsuitability of the above techniques for evaluating the effect of a monomolecular film in suppressing evaporation, 

a method was developed (Harbeck and Koberg, 1959) that is based 

upon both the energy-budget and mass-transfer theories of evaporation. A detailed description of the method is beyond the scope 

of this report, but the basic theory will be described.

The water budget, which is probably the simplest way of measuring evaporation, is based on the fundamental equation inflow minus 

outflow equals change in storage. Evaporation, one of the outflow 

items, can be computed if all other terms in the equation can be
32 EVAPORATION CONTROL RESEARCH, 1955-58

measured. Unfortunately this method can be used at only a few 

reservoirs in the United States, for evaporation in this equation is 

a residual, and small percentage errors in measuring inflow and 

outflow items usually result in an evaporation figure of doubtful 

accuracy.

The energy-budget method is also an inflow-outflow change in 

storage equation, but instead of measuring volumes of water, an 

accounting is kept of all incoming and outgoing energy and the 

change in energy stored in the reservoir. The energy utilized for 

evaporation, one of the outflow items, is again the residual. However, the evaporation item is much larger compared to other 

items in the equation in the energy-budget equation than in the 

water-budget equation. Although a residual, it can be determined 

with adequate accuracy.

A film applied to a reservoir to suppress evaporation does not 

affect the amount of incoming energy, both solar and atmospheric. 

The film suppresses evaporation; this decreases the amount of 

energy utilized for evaporation. The energy that is no longer 

utilized for evaporation must be disposed of by other physical 

processes. The most important of these are back radiation and 

conduction, both of which depend on water-surface temperature. 

When a film is applied, the water surface temperature must rise 

until the energy no longer being utilized for evaporation is disposed by back radiation and conduction. With certain approximations, the mathematical equation is

T0 f-T0 ) = 0 ^ (1) 

in which o-=Stefan-Boltzman constant for black-body radiation

(=1.171X10-7 cal cm~2 deg~4 day-1 ) 

TO = observed water-surface temperature in °C 

TQ = water-surf ace temperature in °C that would have been

observed if film had not been applied 

p=density of evaporated water (=1 cal g" 1 deg"1 ) 

E'= observed evaporation in g cm~2 day"1 (=cm day" 1 ) 

Z/=latent heat of vaporization at T0' in cal g"1 

N=an empirical constant

 w=wind speed in knots

e0 = saturation vapor pressure at T0 in mb

e& = vapor pressure of the air in mb

-K"=an empirical constant

The values of empirical constants N and K are determined during a 

pretreatment calibration period using equations derived from basic 

theory of heat and mass transfer. The only unknown in equation 1
LARGE-SCALE FIELD TESTS 33

is TQ, as e0 is explicitly determined by T0 . Because the relation between T0 and e0 is not linear, a direct solution of equation 1 is impracticable, and it is simpler to assume successive values of T0 with equation 1 balances. Then E, the evaporation that would have occurred 

if no film had been present, can be computed from

Equations 1 an,d 2 are in effect two simultaneous equations which provide a means of solving for the two unknowns, E and T0.

The instrumentation used in the field evaluation studies included 

the following: A total hemispherical radiometer, an Eppley pyrheliometer, a copper-constantan thermocouple psychrometer, a Robinson-type 3-cup anemometer, a Whitney underwater thermometer, 

a reservoir staff gage, a Six's maximum-minimum thermometer, 

and a standard 8-inch rain gage. The output of the radiometer, 

pyrheliometer, and psychrometer were all recorded on a multi-channel recording potentiometer.

The first tests were made at Essar Ranch Lake, about 2 miles 

from Southwest Research Institute. The reservoir was constructed in 1946-^7, and was first filled in 1950. At full pool the 

surface area is about 28 acres, but at the start of the field tests in 

the summer of 1956, the prolonged drought and seepage losses had 

reduced the surface area to less than 4 acres.

During a pretreatment calibration period, June 22 to July 15, 

1956, values of the empirical constants N and K (see equation 1) 

were determined. The seepage loss was computed using the method 

developed by Langbein (Langbein and others, 1951).

For the tests, the desired amount of film-forming material (hexadecanol or octadecanol) was weighed out and apportioned equally 

among eight 2-foot square rafts, constructed of Douglas fir 2 by 

4's and covered with standard window screen (14 x 18 mesh). 

Aluminum screen was used initially; copper bronze screen was 

substituted when it was found that the aluminum screen was soon 

fouled by algae.

The eight rafts were concentrated in the upwind part of the 

lake. Daily readings of the anemometer and staff gage and observations of maximum and minimum water-surface temperatures were 

made by SwRI personnel. Thermal surveys were made at 5-day 

intervals, using the Whitney underwater thermometer. At 18 points 

on the lake, temperatures were measured at the surface and at 

depths of 0.5 foot, 1 foot, and at intervals of 1 foot thereafter. 

A summary of the results is given in the following table.
34 EVAPORATION CONTROL RESEARCH, 1955-58

Results of evaporation studies at Essar Ranch Lake, 1956

Period

June 22 to

July 15

August 1-10..

September

10-20.

October 10-

31.

Treatment

None.

Octadecanol (Adol 62)-...

.....do_. -..........---.....

Hexadecanol (Adol 54)

with 1 percent cupric

stearate.

Amount

used

(pounds

per acre)

2.2

20.0

20.0

Actual

evaporation

energy

budget

method

(feet per

day)

0. 0295

.0251

.0149

.0097

Computed natural evaporation

(feet per

day)

0. 0295

.0261

.0163

.0119

Observed water

surface

temperature (°F)

83.4

85.6

85.3

75.6

Computed natural water

surface

temperature

(Of)

83.4

84.4

83.1

72.3

Saving

in evaporation

(percent)

4

9

18

During the course of the experiment the lake was used for both 

fishing and duck hunting. Apparently neither the fish nor ducks 

were affected by the film. As many as 200 ducks were seen at 

the reservoir at one time.

During the winter of 1957, runoff into Essar Kanch Lake began 

to increase, as pumped ground water that was no longer needed for 

irrigation was stored in the lake. The volume of inflow became 

so large as to cast doubt upon the accuracy of the advected energy 

term in the energy budget equation, and it was therefore decided 

to make further tests at another site.

The next tests were made at McFaddin Keservoir, at the Moss 

Bluff plant of the Texas Gulf Sulphur Co., near Liberty, Tex. 

This lake is somewhat larger than the pond used for the previous 

tests, and during most of the spring and summer of 1957 its surface 

area was 12 to 15 acres. Following a calibration period March 12 

to April 19, 1957, hexadecanol was applied for the first test, which 

continued until June 17. One percent of cupric laurate was added 

to the hexadecanol in an attempt to reduce the consumption of 

the film-forming material by bacteria. The amount of hexadecanol 

actually used (0.64 Ib per acre per month) was determined by 

weighing the material placed in each raft at the beginning of the 

test and again at the end of the test. However, the reservoir overflowed into a drainage ditch on one occasion, and some hexadecanol 

may have been lost. The reduction in evaporation was computed 

to be 5 percent, and the temperature rise was 0.5° C.

The next test was made during the period June 17 to August 5, 

1957. Octadecanol was the film-forming material used, but there 

was no apparent reduction in evaporation. The amount of octadecanol used was 0.78 Ib per acre per month. However, because 

natural evaporation rates in this area are low, owing to prevailing 

high humidity, results may not be very accurate.
LARGE-SCALE FIELD TESTS 35

Because natural evaporation rates are low and relative errors in 

evaluating savings might conceivably be large, it was decided that 

satisfactory tests could not be made at McFaddin Lake. However, 

in many respects the lake was excellent for this purpose, it was 

regular in shape, inflow and outflow were very small, and well 

qualified technical personnel of the Texas Gulf Sulphur Co. were 

available to make observations and service the recording equipment. 

Unfortunately, the high humidity and the hydrogen sulfide from 

the sulfur plant caused frequent malfunctioning of the temperature and radiation equipment, which introduced additional complications.

The equipment was moved to Cement Creek Reservoir at Fort 

Worth in August 1957. Cement Creek Reservoir, which was built 

by Tarrant County Water Control and Improvement District No. 1, 

is used for flood control and has a small permanent pool below the 

level of the uncontrolled morning-glory spillway. During the fall 

of 1957, pretreatment calibration data were obtained. Heavy rains 

during the spring of 1958 caused the application of a film to be 

postponed because of the frequent spilling of the reservoir.

Studies were also made using Leonard Lake near Monte Alto, 

Tex. This lake was originally a highway borrow pit but has been 

filled with water as a result of natural runoff and by drainage from 

the surrounding irrigated area in the Hidalgo and Willacy County 

Water Control and Improvement District No. 1. The lake is 

approximately rectangular in shape and, in 1957, had a surface area 

of about 6 acres.

Instruments were not available to permit the measurement of 

evaporation using the energy budget technique. Radiation data are 

not required for the solution of equation 1, but evaporation (measured by either the energy budget or water budget method), air and 

water-surface temperature, humidity of the air, and wind speed are 

needed. At Leonard Lake an anemometer and a water-surface 

temperature recorder were mounted on a raft on the lake. A hygrothermograph was used to obtain records of air temperature and 

humidity. A water stage recorder was used to obtain a continuous 

record of lake stage. Surface inflow to the reservoir was infrequent and usually small, and it was hoped that with the Langbein 

technique, recorded changes in stage could be separated into the 

two components of evaporation and seepage.

After a 5-week calibration period to determine the values of K 

and N in equation 1, eight drippers, filled with dodecanol (see 

fig. 7) and containing 26 strands of cotton twine as wicks, were 

installed in December 1957.
36 EVAPORATION CONTROL RESEARCH, 1955-58

After 2 weeks, it was noted that although the dodecanol in the 

drippers was still liquid, the drip rate had dropped almost to zero. 

The drippers were readjusted to a faster dripping rate by removing 

one strand of each wick. The rapid spread of the film was evident by the quieting of the waves under it. The effect could be 

easily seen.

Prior to readjusting the drip rate, tests for presence of the film 

indicated its absence except for a strip about 4 feet wide on the 

the lee side of the lake. After readjustment, and overnight operation, during which time the dodecanol solidified in the cans, and 

also formed "icicles" about 4-inches long from the wicks, there 

was still no film on the body of the lake. The film along the lee 

side of the reservoir was about 20 feet wide, however, at this 

point.

The presence or absence of the film was tested by covering an 

area of the water surface with carbon black and adding one drop 

of dodecanol to the center of the covered area. If the carbon 

black is spread very rapidly, there is no film present originally. 

If the carbon black does not spread, a compressed film exists. If 

there is a slow movement of the carbon black, some film is present. 

The degree of compression varies with the rate of movement of the 

carbon black. It should be emphasized that if no film is present, 

the movement of the carbon black is almost instantaneous over a 

distance of at least 4-6 feet.

As a result of heavy rains in January 1958 the dam was overflowed 

and breached. The first test was not long enough to yield significant 

results. After the dam was repaired, another calibration check was 

made, and the second test was begun in April 1958. The number 

of drippers was increased to 18, and gallon cans were used instead 

of the small cans shown in figure 7. The gallon can had a 1/4-inch 

copper tube soldered into the bottom, through which a wick composed of 23 strands of twisted Orion yarn was placed. The second 

test was completed in early May, but the results were inconclusive. 

A third test was begun in mid-May and was completed in August. 

Dodecanol was used as in the earlier tests, except that a different 

brand was tried.

The fact that the results of all the tests at Leonard Lake were 

inconclusive was believed due to the complicated ground-water 

conditions in the area. Although it was possible to determine the 

net seepage into the lake by means of the Langbein technique, the 

seepage rate apparently changed markedly as ground-water levels 

in the area changed. The seepage inflow was at times large compared with evaporation, and it was impossible to separate the total 

change in stage into its two components of seepage and evaporation 

with any reasonable degree of accuracy.
OTHER METHODS OF APPLICATION 37

Although the Leonard Lake tests gave no reliable results insofar 

as reduction in evaporation was concerned, the tests yielded valuable information on dripping and spreading rates. Although increasing the number of dispensers from 8 to 18 did increase the 

film coverage, a complete compressed film was not obtained.

Tests on miscellaneous small reservoirs have utilized two ponds 

sufficiently close to each other so that seepage and evaporation characteristics of both can be assumed to be similar; this eliminates the 

necessity for comprehensive instrumentation. Each pond was 

equipped with staff gages; the pond to be treated was equipped 

additionally with wick-drip applicators. A board holding a thermometer, a rain gage, and a pad of data sheets was set up in the 

immediate vinicity of the ponds; one such board was installed near 

each pond if the ponds were more than a few hundred yards apart. 

The equipment used is shown in figure 10.

OTHER METHODS OF APPLICATION

Effective application of evaporation retardants to a large reservoir is a major technological problem in itself. Rafts and drippers 

have constituted the only two methods investigated to any degree 

in this program; however, in addition to the rafts previously described, other methods of application have been considered for 

future reference.

APPLICATION IN A SOLVENT

The application of a retardant in a solvent has been used on an 

88-acre lake near Nairobi, Kenya. Although the use of kerosene 

in the United States is not desirable, its use in a state of dire 

emergency is possible, and withdrawal of the water below the 

surface followed by the usual chlorination and other purification 

procedures should avoid inclusion of the kerosene in the water. 

Recent communications from Australia indicate that a mixture of 

kerosene, or other hydrocarbon solvent, and ethanol has been used 

to distribute the hexadecanol on a 930-acre reservoir at Broken Hill, 

New South Wales. Dispensers of the type shown in figure 14 were 

used; the valve was replaced later by a capillary tube at the end 

of the outlet. These dispensers, used one to every 80 acres of watersurface, applied 1.6 imperial gallons of solution per unit per day 

(I. W. Wark, written communication January 1958). Wark also 

stated that the reservoir refills only every 3-A years; hence, the 

need for conservation of the water by any means possible is urgent 

and takes precedence over any possible or potential recreational use

550194 O 60___4
38 EVAPORATION CONTROL RESEARCH, 1955-58

Vent

Liquid-level gage (optional)' 

Lug welded to drum 

Control valve

Pivot

Float

P.V.C. tube attached to float

Wind vane

Liquid-level gage 

(optional)

FIGURE 14. Dispensers used in Australia for large reservoirs.

of the reservoir. This criterion is generally not true in the United 

States.

Ethanol has been considered as a solvent and cloud-point depressant for dodecanol, as previously mentioned. It is also a possible solvent for hexadecanol. U. S. Treasury regulations concerning tax-free or specially denatured ethanol must be carefully 

studied in this regard, however.

Other solvent methods of application which have been considered 

are the use of an aerosol-type spray applicator utilizing Freon 

12, or a mixture of Freon 11 and 12, or other fluorinated hydro-
SUGGESTIONS FOR FUTURE WORK 39

carbons; and a low-pressure application system utilizing liquefied 

petroleum gases (butane, propane, or mixtures of these). These 

methods appear somewhat expensive, and in the case of the liquefied 

petroleum gases a fire hazard is also involved.

APPLICATION AS A LIQUID

The use of liquid alkanols has been discussed to some extent in 

the preceding sections. In the following section on "Suggestions 

for Future Work," there are described several new and novel chemical materials that are liquids and believed to be bacteria resistant. 

The use of liquid alkanols as solvents for additional quantities of 

solid materials has also been proposed.

APPLICATION AS A SOLID

In addition to the rafts and the cast cake formulations of alkanols, other cast cake formulations utilizing a polyoxyethylene-polyoxypropylene spreader (Pluronic F-68) have been considered. Some 

formulations of this material with hexadecanol have been used by 

Shulman (written communication, J. A. Langford, February 1956) 

in evaporation control experiments in South America. A preliminary 

test in the Southwest Research Institute laboratory utilizing hexadecanol with 10 percent Pluronic F-68 showed little superiority to 

pure hexadecanol in cool weather.

APPPLICATION AS AN EMULSION

Dressier (written communication, January 1958) has proposed the 

use of a stable dispersion of hexadecanol. This could be applied 

in liquid form; the emulsifying agents could possibly assist in 

spreading the material in cold weather. The toxicological properties of any emulsion or dispersion formulation would have to be 

cleared by the U. S. Public Health Service prior to any large-scale 

use.

SUGGESTIONS FOR FUTURE WORK

Several suggestions were advanced in the course of this work on 

monomocular films for future study as time and circumstances permit, as follows.

THE EFFECT OF IMPURITIES

A good many different hexadecanol-octadecanol and dodecanol 

mixtures were tested in the screening phase of the program. As 

can be seen from table 1, the effectiveness as evaporation retardants for some of them was excellent, others fair, and still others
40 EVAPORATION CONTROL RESEARCH, 1955-58

poor. A fundamental study on. this aspect is an indicated possible 

program. Artificial mixtures of pure materials are suggested.

BACTERICIDES AND BACTERIOSTATS

It was not possible to evaluate all the bacteriostatic or bactericidal materials or intermediates on hand during the screening or 

field-screening work. Evaluation of these and other bactericidal 

materials compounded with the alkanols is in order. Irradiation 

of the evaporation retardants prior to use has been suggested.

BACTERIA-RESISTANT MATERIALS

The following general types of compounds have been proposed as 

being evaporation retardants that are, by their structure, potentially 

immune to, or less susceptible to biochemical oxidation.

1. Monosilanols RSiH2OH, where R is a straight-chain aliphatic 

hydrocarbon chain of at least 10, and preferably 16 or more carbon 

atoms.

2. Primary alkanols containing carbon chains with odd numbers 

of carbon atoms. It is understood that at least two petroleum 

companies are obtaining 1-tridecanol from oxo-process oxidation. 

Longer chain alkanols are possible.

3. Omega-unsaturated primary alkanols. One such, 10-undecenl-ol is obtained by dry distillation of castor oil and subsequent 

reduction of esters of the resulting acids. These have the general 

formula: H2C = CH(CH2 ) x CH2OH, and have been covered by invention disclosure.

4. Omega-cyclopropanoalkanols. The cyclopropane nucleus is an 

integral part of the chemical structure of pyrethrins; also, allethrin, 

and lactobacillic acid. Such a structure should be bacteria resistant, 

but not toxic to warm-blooded mammals, including man. Toxicity 

to fish should be checked, however. The general formula is:

H2C C (CH2) x CH2OH

Y

H2

THE EFFECTS OF WIND

A recent communication from Australia (I. W. Wark, written 

communications, January 1958) advises that: ". . . the solvent process does not seem to behave badly when the wind velocity is below 

2 mph or if it is above 10 mph. This has been traced to poor 

spreading of the hexadecanol-solvent mixture."
SCREENING APPARATUS 41

This investigation has shown that effects of wind on the film are 

a major problem, especially on larger reservoirs at any wind 

velocity. Windbreaks, both natural and artificial, around the reservoir and networks of ropes, optionally saturated with hexadecanol 

or having cakes of hexadecanol cast on the rope, placed on the 

water surface are two proposed mechanical aids.

FIELD STUDIES

More data from small reservoirs and ponds, especially in arid 

areas such as the Sonoran Desert are needed, as it is in arid areas 

where the monofilm technique will be of most value. The use of a 

film in areas of high humidity does not appear to be economically 

practical, unless a prolonged drought (such as 1947-1956) occurs 

in the area.

SCREENING APPARATUS

TECHNICAL DETAILS AND SPECIFICATIONS

Trough (thermostat). Sixteen feet long, 12 inches wide, 10 inches 

deep; constructed of 16-gauge galvanized sheet iron; Vk'hid1 drain 

soldered into the bottom at one end.

Insulation. One-inch fiberglass wrapped in 5-mil sheet poly vinyl 

copolymer, and held in place by 2-inch spring binder clamps and 

oak strips %-inch wide by %-inch thick.

Circulating pump. Motor-pump, rated at 10 gpm, and driven by 

a i/4-HP electrical motor; !/2-incn black pipe circulation system.

Thermoswitch. 10 amp., 115 volt rating.

Heater. Low drift flexible immersion heater, 750 watt.

Air system. Driers were constructed of 3-inch black pipe, 4- 

feet long; connected to the system through i/^-inch unions to facilitate removal for regeneration of the silica gel desiccant.

Manifolds were standard chrome-plated brass hose connectors, %- 

inch male pipe threads.

Connecting pipelines were !/2'inch black pipe. Copper or galvanized pipe is recommended for future installations.

The pressure regulator had an overall diameter of 9 inches.

DESICCANT REGENEKATION

The exhausted silica gel (10-12 pounds per drier) was removed 

from the drier and regenerated in an electric oven at 350° F. The 

material was spread out in shallow trays to facilitate the operation.

During the operation of a test bank in the screening apparatus, it 

was customary to alternate the driers; the silica gel from one was 

regenerated while the other drier was in use.
42 EVAPORATION CONTROL RESEARCH, 1955-58 

TOXICITY STATEMENT

The following statement concerning toxicity of hexadecanol and 

dodecanol was received from the Kobert A. Taft Sanitary Engineering Center, Cincinnati, Ohio.3 

A. Opinion on toxicity of hexadecanol proposed for use in evaporation control

It is our opinion that no hazard to public health should result from the use 

of hexadecanol in the amount and manner proposed to produce a monomolecular 

film on water surfaces in evaporation reduction.

Although there is no report of information known to us on the long-term 

ingestion studies of hexadecanol, this material in one form or another has been 

used in a domestic manner for many years without evidence of detrimental 

effects on the health of individuals. Indirect, but important, evidence indicating safety in the use of the long-chain alcohols is presented in the work of 

Treon 4 of the Kettering Laboratory. Treon found that the oral toxicity of 

aliphatic straight-chain alcohols decreased sharply at the C-10 chain-length. 

This implies that alcohols of longer chain-length, because of lessened solubility 

and other characteristics, would have still further reduced toxicity. Supporting evidence is contained in the work of Stetten and Schoenheimer 5 who noted 

that hexadecanol is oxidized to the corresponding fatty acid, palmitic acid. 

This is a component of normal fat which, of course, is a common foodstuff. 

Additional supporting evidence is the information provided by A. J. Lehman,6 

who cited evidence that amounts of hexadecanol up to 0.1 percent in the diet 

were completely metabolized (like a fat) and that the Food and Drug Administration saw no objection to application of hexadecanol to produce monomolecular layers, provided the alcohol is pure and the materials applied with it are 

harmless.

Octadecanol, tetradecanol, and the unsaturated C-18 alcohols, often associated with commercial hexadecanol, are normal metabolites of commonly ingested foodstuffs and, consequently, would not be expected to present a health 

hazard upon ingestion in any reasonable amount.

Accordingly, in view of (a) the lack of direct evidence of the hazard to 

health upon ingestion, (b) certain evidence favoring the view of its probable 

innocuousness, and (c) the improbability of ingestion of any but extremely 

trivial amounts as a result of the method of use, it does not seem reasonable 

to anticipate that any hazard to health would result from its use for the purpose of producing monomolecular films on water surfaces, and under the conditions proposed for this use, even though exposure was to be for the lifetime 

of the individual.

3 Written communication, U. S. Public Health Service, Department of Health, Education, and Welfare.

 * Written communication from J. F. Treon, The Kettering Laboratory, Cincinnati, Ohio.

5 Stetten, DeWitt, Jr., and Schoenheimer,. Rudolf, 1940, The biological relations of the 

higher aliphatic alcohols to fatty acids : Jour. Biol. Chemistry, v. 133, p. 346-57.

6 Oral communication from Arnold J. Lehman, chief, Division of Pharmacology, Food 

and Drug Administration.
TOXICITY STATEMENT 43

It is necessary to add that chemicals used with hexadecanol could conceivably 

produce a mixture with enhanced toxic properties. Therefore, preparations 

proposed for use should be independently reviewed for possible toxicity potential.

B. Opinion on toxicity of dodecanol proposed for use in evaporation control

Available information is inadequate to justify a favorable opinion on the use 

of dodecanol for the purpose of producing a monomolecular film on water surfaces in evaporation reduction.

The evaluation of acceptability of dodecanol (lauryl alcohol) as an aid in 

control of evaporation of water from reservoirs is based on the following information which constitutes all of that available to the above-signed at the 

present time. Data may be obtained from other sources, such as the Food and 

Drug Administration or in certain company files, but it is believed that sufficient information is already available for the development of an opinion.

The unpublished work of Treon 7 on the minimal lethal oral toxicity for 

animals using single doses of the aliphatic alcohols, including dodecanol, indicated a sharp decrease in toxicity at the C-10 chain-lengths (decanol). One 

infers from this that the alcohols of longer chain-lengths, because of lessened 

solubility and consequent absorbability, would have still further reduced toxicities. The irritant properties of the alcohols, including dodecanol, are not reduced, however. 8

Lauryl alcohol is a closely related reduction product of a constituent of coconut oil. I have received information 8 that a product of lauryl alcohol, lauryl 

gallate, has been approved by the Federal Drug Administration for use as an 

antioxidant in foods. This approval was based on information of the type 

described by Allan and DeEds 9 in which long-term feeding experiments of 

albino rats, involving concentrations of lauryl gallate as high as 0.5 percent 

in the diet produced no observable adverse effects; higher levels definitely produced toxic effects. A Japanese report 10 involving a toxicity study in rats of 

a series of fatty alcohols, from C6-C18 including dodecanol, indicate a toxic 

effect was obtained with dodecanol, but not with hexadecanol, under similar 

conditions of test. These results are at variance with the above-quoted American Experience, and could possibly be attributed to dietary inadequacies in the 

Japanese study.

On the other hand, the irritant properties of lauryl alcohol are well known. 

Those of coconut oil are ascribed to its lauryl acid ester component. The irritant property of dodecanol is a plaguing one in the light of current knowledge 

that irritants may enhance the carcinogenic!ty of cancerigenic agents.

It is therefore believed that before the use of dodecanol can be approved for 

the purpose of producing monomolecular films on water surfaces, further toxicological studies data justifying a favorable opinion should be obtained.

? Written communication from Joseph F. Treon, past chief toxicologist, Kettering 

Laboratories, Cincinnati, Ohio.

8 Written communication from John A. Zapp, Jr., Haskell Laboratory, E. I. DuPont 

de Nemours and Company, Wilmington 98, Del.

9 Alien, S. C., and DeEds, F., 1951, The chronic toxicity of lauryl gallate : Jour. Am. 

Oil Chemists' Soc., v. 28, p. 304.

10 Miyazaki, M., 1955, Nutritive value and toxicity of saturated alcohols with 6-18 

carbon atoms: Jour. Agr. Chem. Soc., Japan, v. 29, p. 501.
44 EVAPORATION CONTROL RESEARCH, 1955-58

REFERENCES CITED

Adam, N. K., 1941, The physics and chemistry of surfaces: 3d ed., Oxford

Univ. Press. 

Archer, R. J., and LaMer, V. K., 1954, The effect of monolayers on the rate of

evaporation of water: New York Acad. Sci. Ann., v. 58, p. 807-829. 

Grundy, F., 1957, The use of cetyl alcohol to reduce reservoir evaporation:

Inst. Water Engineers Jour., v. 11, p. 429-437; East African Meteorol. Dept.

Mem., v. 2, no. 11, p. 1-11. 

Harbeck, G. E., Jr., and Koberg, G. E., 1959, A method of evaluating the effect

of a monomolecular film in suppressing reservoir evaporation: Jour. Geophysics Research, v. 64, no. 1, p. 89-93. 

Hedestrand, G., 1924, The influence of thin surface films on the evaporation of

water: Jour. Phys. Chemistry, v. 28, p. 1245-1252. 

Kohler, M. A., 1954, Lake and pan evaporation, in Water-loss investigations:

Lake Hefner studies, technical report: U. S. Geol. Survey Prof. Paper 269,

p. 127-148; reprint of U. S. Geol. Survey Circ. 229, 1952. 

Kohler, M. A., Nordenson, T. J., and Fox, W. E., 1955, Evaporation from pans

and lakes: U. S. Weather Bur. Research Paper 38.

Langbein, W. B., Hains, O. H., and Culler, R. C., 1951, Hydrology of stockwater reservoirs in Arizona: U. S. Geol. Survey Circ. 110. 

Langmuir, Irving, 1917, The shapes of group molecules forming the surfaces of

molecules: [U. S.] Natl. Acad. Sci. Proc., v. 3, p. 251-257. 

Langmuir, Irving, and Langmuir, D. B., 1927, The effect of monomolecular

films on the evaporation of ether solutions: Jour. Phys. Chemistry, v. 31,

p. 1719-1731. 

Langmuir, Irving, and Schaefer, V. J., 1943, Rates of evaporation of water

through compressed monolayers on water: Franklin Inst. Jour., v. 235,

p. 119-162. 

Ludzack, F. J., and Ettinger, M. B., 1957, Biological oxidation of hexadecanol

under laboratory conditions: Am. Water Works Assoc. Jour., v. 49, p. 849-

858. 

Mansfield, W. W., 1953, Effect of surface films on the evaporation of water:

Nature, v. 172, p. 1101.

 1955, Summary of field trials on the use of cetyl alcohol to restrict 

evaporation from open storages during the season 1954-55: Commonwealth 

Scientific and Industrial Research Organization, Div. of Indus. Chemistry, 

serial 74, 8 p., Melbourne, Australia.

 1956, The use of hexadecanol for reservoir evaporation control, in Proceedings of First International Conference on Reservoir Evaporation Control, San Antonio, Tex., April 14: Southwest Research Institute.

Rideal, E. K., 1925, The influence of thin surface films on the evaporation of 

water: Jour. Phys. Chemistry, v. 29, p. 1585-1588.

U. S. Geological Survey, 1954, Water-loss investigations: Lake Hefner studies, 

technical report: U. S. Geol. Survey Prof. Paper 269; reprint of U. S. Geol. 

Survey Circ. 229, 1952.

Weitzel, Gunther, Fretzdorff, A. M., and Heller, Siegfried, 1951a, Monomolecular 

films of several methylated palmitic acids, pt. A: Hoppe-Seyler's Zeitschr. 

physiologische Chemie, v. 288, p. 189-200.

Weitzel, Gunther, Fretzdorff, A. M., and Heller, Siegfried, 1951b, Monomolecular films of several methylated stearic acids, pt. B: Hoppe-Seyler's 

Zeitschr. physiologische Chemie, v. 288, p. 200-215.
INDEX

Page 

Abstract......_____ _________ 1

Acids, laboratory tests of. -_____--.. 11-12 

Alkanols, laboratory tests of____-..-__ 9-10 

Amides, laboratory tests of-.______.-..- 12 

Amines, laboratory tests of- _____-___ 11

Bacteriocides, compounds used for______ 16

copper salts...-.. ___..._._ 15

Bacteriocidic additives, use of..___ 15-16,40

Bacteriostatic additives, use of.-... 15,40

Cement Creek Reservoir, tests at.______ 35

Cloud point, determinations_________ 19-20

Copper salts, preparation of..________ 16

solubility in hexadecanol...-_ . 15

Desiccant regeneration_ ________ 41

Dihydroxy compounds, laboratory tests of._ 10

Dodecanol, cloud point for__________. 20

field tests for..-..--.--.--.-.__...---... 35-37

flow rates_._____ _____ __.. 25, 26

Energy budget method of determining rate of

evaporation......__._ 6,31-32

Essar Ranch Lake, tests at..._________ 33-34 

Esters, laboratory tests of.....________ 12

Ethylene oxide condensation products, laboratory tests of... ______.... 10

Evaporation control, theory._.____- 4-7 

Evaporation pans, use of, in testing_. 31 

Evaporation rate, method of determining .. 6 

Evaporation retardants, application as a

emulsion_ 39 

application in a solvent_ 37-39 

application of liquids.. ...-._.. 18-19,39,40 

application of solids.--. _________ 27,39 

composition.. -.._ 9-12 

determination of cloud point____ ___ 19-20 

rejected compounds.---________ 12 

results of field tests. ________ 14 

results of laboratory tests________... 9-12 

trade names___._____________ 9-12

Field studies, need for______________ 41

Field tests, instrumentation for________ 33

large scale..._________________ 30-37

problems__________________ 30

reactions of bactericides_______ __ 16

use of ponds and reservoirs... ...- 30-31

use of 10-foot tanks.._________. 13-15,30

Future work, suggestions for.... ______ 39-41

Hexadecanol, cloud point for .. 

effect of adding polyethylene to 

results of tests.... 

Hydrophobic portion of the molecule, definition.. .. 

Hydrophylic groups, formulas --- 

Hydrophylic portion of the molecule, definition. .-. 

Page 

20 

28 

34

4

4

Impurities, effect of----- ._------- - 39-40

Instrumentation for field tests.. 33 

Introduction..... -. 1-3

Ketones, laboratory tests of- 11

Laboratory tests of organic chemicals. -- 7-9 

Laboratory work, stages.. 7 

Leonard Lake, tests at...-. 35-37

McFaddta Reservoir, tests at. -.... 34 

Mononuclear film, calculation of effect of. .--- 5-6 

effect of wind on _ ...-.- .- 7 

formed by hydrophylic groups.... 4-5 

method of application.. - 6-7,18-19,27,37-40 

test for presence of.. 36

Nitriles, laboratory tests of. 10

Pellets, preparation of-_ 27

Phenols, laboratory tests of 11

Polyhydroxy compounds, laboratory tests of- 10

Rafts, construction..-..__-_ --- 27-28,29 

use of, in field tests,---. --------------- 33-34

Rate of evaporation, method of determining. 6,31-33 

References cited... 44

Screening apparatus, details and specifications. 

Silicones, laboratory tests of.. 

Test for evaporation retardants. See Laboratory tests and Field tests.

Toxicity, considerations of - 28 

Toxicity statement----------.- ---------- 42-43

Trade names of evaporation retardants- 9-12

Water budget, rate of evaporation determined

by 31-32

Wick dispensers, tests.. 21-26 

Wick materials.-..-----_. 25

Wind, effects of..--- 17-18,40-41

o

45