UNITED STATES DEPARTMENT OF COMMERCE • Charles Sawyer, Secretary

NATIONAL BUREAU OF STANDARDS • E. U. Condon, Director

Nomograms for Obtaining the Compound Composition

of Hydrated Limes From the Oxide Analysis

by Ernest M. Levin

r

National Bureau of Standards Miscellaneous Publication 196

Issued December 30, 1949

For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C. Price 25 cents

U. S. GOVERNMENT PRINTING OFFICE : 1950

UNITED STATES DEPARTMENT OF COMMERCE • Charles Sawyer, Secretary

NATIONAL BUREAU OF STANDARDS • E. U. Condon, Director

mograms for Obtaining the Compound Composition

of Hydrated Limes From the Oxide Analysis

by Ernest M. Levin

National Bureau of Standards Miscellaneous Publication 196

Issued December 30, 1949
Contents

Page

I. Introduction 1 II. Derivation of Equations 2

III. Description of Nomograms 2

IV. Illustrative Examples 3

V. Accuracy of the Nomograms 5

VI. References 5

TITLES OF NOMOGRAMS

1 . General nomogram for obtaining the compound composition of any commercial hydrated lime from the oxide analysis.

2. Special nomogram for obtaining the compound composition of regularly

hydrated and highly hydrated dolomitic limes from the oxide analysis.
Nomograms for Obtaining the Compound Composition

Of Hydrated Limes From the Oxide Analysis

by Ernest M. Levin

Two nomograms are presented for rapidly obtaining the compound composition of

hydrated limes from the oxide analysis. The general nomogram can be applied to any

commercial hydrated lime and gives values accurate to within 0.3 percent. The special

nomogram is applicable only to regularly hydrated and highly hydrated dolomitic limes and

is accurate to within 0.1 percent. The equations for calculating the compound composition

are derived, and the significance of the unhydrated oxide content is stressed.

I. Introduction

Hydrated limes can be classified broadly into

three major groups on the basis of total magnesia

content [1]

1 as follows: (1) high-calcium, containing less than 5-percent total magnesia; (2)

dolomitic, containing more than 25 percent of

magnesia; and (3) magnesian, containing between

5 and 25 percent of magnesia. Dolomitic limes can be further subdivided on the basis of the

degree of hydration of the magnesia, as follows:

regularly hydrated,2 in which the major portion

of the magnesia has been left unhydrated, and

highly hydrated,3 in which the major portion of

the magnesia has been hydrated.

Studies [4J have been in progress for several

years at the National Bureau of Standards of a

particular type of plaster failure, associated only

with regularly hydrated dolomitic limes and characterized by the formation of bulges, or large

blisters, in the white-coat. It has been found

that this type of failure results from a delayed

expansion of the set, white-coat plaster. The

regularly hydrated dolomitic lime that was mixed

originally with the calcined gypsum and water to

compound the wet plaster was not completely hydrated; and, consequently, the plaster contained

unhydrated magnesium oxide (MgO) at the time

of application. The unreacted MgO continues to

hydrate slowly after the plaster has set, eventually

causing the disruptive expansion of the white-coat.

As an outcome of these studies, the Bureau,

assisted by other Government agencies, formu1 Figures in brackets indicate the literature references at the end of this paper.

2 Also designated as normal hydrated lime [2].

3 Also designated as special hydrated lime [3].

lated a specification that would exclude partially

hydrated dolomitic limes containing a high percentage of unhydrated oxides. Accordingly, the

following tentative amendment to Federal Specification SS-L-351 for hydrated lime [5] is in

effect: "The total free (unhydrated) calcium oxide

(CaO) and magnesium oxide (MgO) in the hydrated product shall not exceed 8 percent by

weight (calculated on the 'as received' basis)".

The 8-percent limit of the unhydrated oxide in

hydrated limes has been included in recent specifications of the American Society for Testing

Materials [3] and in those of the American Standards Association [6], for the hydrated lime to be

used in white-coat plaster.

Numerous manufacturers of regularly hydrated

dolomitic lime are producing at the present time

a more completely hydrated lime that meets the

8-percent maximum limit. In most instances the

additional hydration is accomplished by treating

the calcined limestone in an autoclave maintained

at an elevated temperature and pressure. This

type of lime has been referred to earlier in the

paper as highly hydrated.

Determination of the unhydrated oxide content

of a lime is of obvious importance in regard to

the 8-percent limit, both to the manufacturer and

to the prospective purchaser of highly hydrated

dolomitic lime. Investigations [7] carried on at

the Bureau have established a method for calculating the compound composition, including the

unhydrated oxide content, from the chemical

analysis. The chemical analysis includes determinations for "free" Hc.0, combined H20, CO*,

Si02 , E2 3 , CaO, and MgO.

856375—49

1
II. Derivation of Equations

The method of calculating the compound composition is based essentially on the premise that

CaO lrydrates completely before MgO and then

carbonates before MgO [7]. In the calculations,

C02 (usually under 2%) is allotted to an equivalent

amount of CaO, to obtain the amount of CaC03 present. The remaining CaO is allotted to an

equivalent amount of combined H2 0, to obtain the

amount of Ca(OH)2 present. The remaining

combined H2 is allotted to an equivalent amount

of MgO, to obtain the amount of Mg(OH)2 present. Finally, the remaining MgO represents

the unhydrated oxide content.

If the amount of combined H2 is insufficient to

account for all of the available CaO, some of the

CaO is also unhydrated. In this event the

combined H2 is allotted to an equivalent amount

of CaO to obtain the amount of Ca(OH)2 present.

The remaining CaO exclusive of that which is carbonated is unhydrated, and this value is adde

to the MgO to obtain the total unhydrated oxides.

It should be noted that in the calculations the

Si02 and R2 3 are considered uncombined; but,

fortunately, only a small percentage of these

oxides is usually present.

In the following derivation of the percentage of

unhydrated oxide in a lime, the formula for the

oxide represents the percentage of that component

present. Also, the derivation is carried out only

for the most usual case, in which all of the CaO is hydrated.

CaO equivalent to C02 =1.275 C02 CaO remaining =CaO— 1.275 C02 Combined H2 equivalent to CaO =0.3213(CaO-1.275 C02 ) remaining

Combined H2 remaining =Comb. HoO- 0.32 13 (CaO -1.275 C02) Hydrated MgO =2.238 [Comb. H2O-0.3213(CaO-1.275 C02 )J Unhydrated MgO (percent) =Total MgO-2.238 [Comb. H>O-0.3213(CaO-1.275

C02)]

After the above calculations have been performed for determining the percentage of un- hydrated oxide, the compound composition isobtained simply by addition or subtraction of the

appropriate terms, as follows:

CaC03 =C02 Ca(OH)2 = (CaO remaining)

Mg(OH) 2 = (Combined H2 remaining)

Unhydrated MgO= (Total MgO)

+ (CaO equivalent to C02) + (Combined H2 equivalent to CaO remaining)

+ (Hydrated MgO) — (Hydrated MgO) (Value obtained from the last step

in the derivation)

The purpose of this publication is to present two mined from the oxide analysis, thus saving time

nomograms from which the compound composition and labor of calculation,

of a hydrated lime can be easily and rapidly deterIII. Description of Nomograms

The general nomogram (nomogram 1) is designed to give the compound composition of any

commercial hydrated lime, from the oxide analysis.

It can be applied to limes of the high-calcium,

magnesian, and dolomitic groups, with an accuracy

of better than 0.3 percent.

The special nomogram (nomogram 2) is designed

so as to give values of the compound composition

accurate to within 0.1 percent, but the nomogram

can be applied only to the regularly hydrated and

highly hydrated dolomitic limes. Not only are the scale divisions in nomogram 2 larger than for

nomogram 1, but also a better disposition of the

scales, themselves, has been achieved.

2
IV. Illustrative Examples

Figure 1 illustrates the method of using nomogram 1 for obtaining the compound composition

of a hydrated lime, as applied to a high-calcium

hydrate.

The oxide analysis of the lime is as follows:

OXIDE ANALYSIS

Percent C02 0. 70

CaO 72. 60

Combined H2 23. 06

Total MgO 1. 04

Percent "Free" H,0 0. 53

SiO-2 . 74

R2O3 - 60

Subtotal 97. 40

Subtotal 1. 87

Total 99. 27

On the scale for C02 , locate the point a, cor- responding to the value of 0.70 percent. At the

intersection of the horizontal projection from

point a with the scale for CaC03 , read the equivalent percentage of CaC03 (1.6). On the scale

for CaO, locate the point b, corresponding to the

value of 72.6 percent, and lay a straightedge across the nomogram from a to b. At the intercept,

point c, read the percentage of Ca(OH)2 (95.0).

On the scale for combined H2 0, locate the point d,

corresponding to the value of 23.1 percent. Lay

the straightedge through points c and d, and locate

the point e, on the scale for hydrated MgO. On

the adjacent scale, read the equivalent percentage

of Mg(OH)2 (0.0). On the scale for total MgO,

locate the point /, corresponding to the value of

1.04 percent, and lay the straightedge across the

nomogram from e to Finally, at point g, the

intersection of the line ef with the scale for unhydrated MgO, read the percentage of unhydrated

MgO (1.0).

Total MgO

0-

25

CaO

r 75

5-§-70

65

-60

20-1-55

•50

30^5

35 j -40

CotOHjj

Hydra ferf MgOj MgfOHjj

--AZ 28^40

26^38

24-

Figure 1. Illustrative example of the -procedure for using nomogram 1 {general nomogram) to obtain the compound

composition of a hydrated lime, as applied to a high-calcium hydrate.

OXIDE ANALYSIS

Percent CO2- 0.70 CaO_ 72.60 Combined H2O 23.06 Total MgO. 1.04

Subtotal 97.40

Percent "Free"H2 0.53 S1O2 — - 74 R2O3 _ .60

Subtotal 1.87

Total 99.27

PROCEDURE

1. Locate line ab (C02 , % to CaO, %): Percent At right of (a) read CaC03 1.6 At (c) read Ca(OH) 2 95.

2. Locate line cd (Ca(OH)2, % to combined H2O, %) and extend

to e (hydrated MgO, %): At (e) read Mg(OH)2 _ . 3. Locate line ef (Mg(OH) 2 , % to total MgO, %): At (g) read unhydrated MgO 1.

Subtotal 97.

3
Figure 2. Illustrative example of the procedure for using nomogram 2 {special nomogram) to obtain the compound composition

of a hydrated lime, as applied to a regularly hydrated dolomitic lime.

OXIDE ANALYSIS

Percent C02 0.63 CaO 46.72 Combined H2 17.96 Total MgO 33.08

Subtotal 98.39

Percent "Free" H2 0.30 Si02 .94 R2O3 .36

Subtotal... 1.60

Total 99.99

PROCEDURE

1. Locate line ab (CO2, % to CaO, %): Percent At (a) read CaCOs 1.4 At (c) read Ca(OH) 2 60. 7

2. Locate line erf (Ca(OH)2,% to combined H2 0,%) and extend to e (hvdrated MgO,%):

At (e) read Mg(OH)2 10. 4

3. Locate line ef (Mg(OH) 2 ,% to total MgO,%):

At (g) read unhydrated MgO 25.

8

Subtotal 98.3

4
Figure 2 illustrates the method of using nomogram 2 for obtaining the compound composition

of a hydrated lime, as applied to a regularly

hydrated dolomitic lime.

The oxide analysis of the lime is as follows:

Percent C02 0. 63

CaO 46. 72

Combined H2 17. 96

Total MgO 33. 08

. Subtotal 98. 39

Percent "Free" H2 0. 30

Si02 - 94

R0O3 • 36

Subtotal 1. 60

Total 99. 99

On the scale for C02 , locate the point a, corre- sponding to the value of 0.63 percent. On the

adjacent scale read the equivalent percentage of

CaC03 (1.4). On the scale for CaO, locate the

point b, corresponding to the value of 46.72 percent, and lay a straightedge across the nomogram

from a to b. At the intercept, point c, read the

percentage of Ca(OH)2 (60.7). On the scale for

combined H2 0, locate the point d, corresponding

to the value -of 17.96 percent. Lay a straightedge

through the points c and d, and locate the point e, on the scale for hydrated MgO. On the adjacent

scale read the equivalent percentage of Mg(OH)2 (10.4). On the scale for total MgO, locate the

point /, corresponding to the value of 33.08 percent, and lay the straightedge across the nomogram from e to f. Finally, at point g, the intersection of line ef with the scale for unhydrated

MgO, read the percentage of unhydrated MgO

(25.8).

To a certain extent the nomograms also provide

for the unusual case in which the combined H2 is insufficient to account for all of the available

CaO, that is, none of the MgO is hydrated and

some unhydrated CaO is present. For such a

case, the point e (figs. 1 and 2) on the appropriately

established line c-d-e will be located on the two

adjacent scales designated as unhydrated CaO and

equivalent Ca(OH)2 . The unhydrated CaO value

must then be added separately to the total MgO

in order to obtain the total of unhydrated oxides.

The reading on the Ca(OH)2 scale must also be

corrected by subtracting from it the Ca(OH)2 equivalent of the unhydrated CaO.

V. Accuracy of the Nomograms

Comparison of the compound composition

obtained both from the full-sized nomogram and

by calculation, for the two examples cited, is given

in the following tabulation:

Compound

High-calcium hydrated lime Regularly hydrated

dolomitic lime

Nomogram 1 Calculated Nomogram 2 Calculated

Percent Percent Percent Percent CaCOs 1. 6 1. 59 1. 4 1. 43

Ca(OH) 2 95. 94. 75 60. 7 60. 67

Mg(OH) 2 . . 07 10. 35 10. 39

Unhydrated MgO_ 1. . 99 25. 82 25. 90

Total. 97. 6 97. 40 98. 27 98. 39

The reading error for nomogram 1 is under 0.3

percent and that for nomogram 2 is under 0.1 percent. The nomograms presented here provide an

accurate and rapid means for obtaining the compound composition of hydrated limes and should

be especially helpful to the analyst making numerous routine determinations.

The author expresses appreciation to Marcella

Lindeman Phillips of the National Bureau of

Standards, whose lectures on the subject of

nomography motivated this work.

VI. References

[1] L. S. Wells, W. F. Clarke, and E. M. Levin, Expansive

characteristics of hydrated limes and the development of an autoclave test for soundness, J. Research

NBS 41, 179 (1948) RP1917.

[2] Tentative Specifications for Normal Finishing Hydrated Lime; ASTM Designation: C6-46T. ASTM

Standards, Part II, 1304 (1946); and Tentative

Specifications for Hydrated Lime for Masonry Purposes; ASTM Designation: C207-46T (Type N—

normal hydrated lime for masonry purposes)

ASTM Standards, Part II, 1308 (1946).

[3] Tentative Specifications for Special Finishing Hydrated Lime; ASTM Designation: C206-46T.

ASTM Standards, Part II, 1306 (1946); and Tentative Specifications for Hydrated Lime for Masonry

Purposes; ASTM Designation: C207-46T (Type S—

special hydrated lime for masonry purposes) ASTM

Standards, Part II, 1308 (1946).

[4] L. S. Wells, W. F. Clarke, E. S. Newman, and D. L. Bishop, Investigation of failures of white-coat

plaster. Publication pending.

[5] Proposed amendment to Federal Specification SS-L351 for lime; hydrated (for) structural purposes.

Date of amendment, Feb. 2, 1940.

[6] Standard specifications for gypsum plastering including

requirements for lathing and furring, American

Standards Assn. A. 42.1-1946.

[7] L. S. Wells and K. Taylor, Hydration of magnesia in dolomitic hydrated limes and putties, J. Research

NBS 19, 215 (1937) RP1022.

Washington, July 28, 1949.

5

856375 O - 49 (In envelope)

UNITED STATES DEPARTMENT OF COMMERCE, Cbarlo Sawyer, Secretary NATIONAL BUREAU OF STANDARDS, E. U. Condon. Dlnctor

CaO

75

Ca(0H)2

Hydrdfed

MgO

30=

5- : 70

10-= =-65

15-= =-60

20 . 55

25 -50

30 45

r94

=90

=88 =86

=84

=82

=80 = 78 m=74

=72 : 70

^68 =66 =64

:62 = 60

=58

^56 =54

=52 =50

=48 =46 ;44 : 42

=38

Combined H2

Unhydrafed

0+246

8?

Iff 125

14^

!6l

18 20f

22^

= 24Hr

261

2830=f

32

34

C02

CaC05 r0 T2 H +67

24-1

e 3

22*4 ^

'#6 4/4

15 16 #7 116

14 -|Uil8

124

14-E 2

40

Nomoj-om 1. Genciol nomogrom Fo- obtoming rf|< compound eompoul.on ol ony eomm«.

e , Q hyd'olcd lime liom Inc o,.dt onolym

|To occomoany Notional Bui«u of Slondo'di Mik 196. .uu.d D*ccmbt> 30. 19491

UNITED STATES DEPARTMENT OF COMMERCE, Charles Sawyer, Secretary NATIONAL BUREAU OF STANDARDS, E. V. Condon, Director

Total

25-r

CaO

52

751 Ca(0H)2

cf—

—5(J '-61

^66

28- r65 L 64

r63

2977 48 r62

1-6!

-fin _ uu 30 7747 - CiQ -

^58

31 7746

r57

^56

r55

3277 45

= 54

=-53 _ JL

337 =51 — ou

34-7-43

=-49

^-48

^47

35-_ -42 ^46 = 45

I44

36-_ 7^1 -43

37- -40

co2 o5-

=

6-

CaC03 r

f- 23

\\5

-I 6

:§-7

-=-10 7 12

^13

Combined H £

28 -r 1 If 2 7# 34

26 === 56

25^7

Unhydrafed

MgO

r

16 8

--9

10 23^-4 12 22^13

ft- 14 Sl5

16

18 | r

20

22

17^-23

j-24

1-25

-#27

28

29 jL 30

3^731

?32

33

r34

^35

36

Hydrated M5

30-

29-

28

27

26

25

24-

23

22

21

20

19

18

17

16-

15-

14-

12-=

M5(0Hj2

1058

7^

6^5432I

,-o-

-i. / iro 2^

3- 3

43

42

E-41

40

^39

38

37

-36

35

34

33

32

31 - 30

29

28

27

26

25

24

23

22

21

20

19

18

17 - 16 - 15 - 14 - 13 - (2 - II - 109876S43I -Ot-

't 2 i?O

Nomogram S. Special nomogram lor obtaining the compound composilron ol regularly hyd'aled and highly hydialed dolomilic limes from the oxide onolysis.

[To accompony National Bureau ol Srandaidt Mittellaneoui Publicolior. 196. iflUtd Decimbsf 30. 1 949|
Nomogram 1. General nomogram for obtaining the compound composition of any commercial

hydrated lime from the oxide analysis.

[To accompany National Bureau of Standards Miscellaneous Publication 196, issued December 30, 1949]

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