A Field Chromatographic 

Method for Determination 

of Uranium in Soils 

and Rocks 

GEOLOGICAL SURVEY BULLETIN 1036-L 
A Field Chromatographic 

Method for Determination 

of Uranium in Soils 

and Rocks 

By CHARLES. E. THOMPSON and I-I. W. LAKIN 

A CONTRIBUTION TO GEOCHEMISTRY 

GEOLOGICAL SURVEY BULLE'T'IN 1036-L 

A rapid and inexpensive field method for 

determination of trace qu·antities of 

uranium in soils and rocks. 

UNITED STATES GOVERNMENT PRINT! NG OFFICE, WASHINGTON : 1957 
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 

Washlngton 25, D. C. - Price 15¢ (paper cover) 
CONTENTS 

Page 

Abstract__________________________________________________________ 209 

Introduction______________________________________________________ 209 

Reagents and apparatus____________________________________________ 210 

Procedure________________________________________________________ 211 

Preparation of sample solution.__________________________________ 211 

Prepn,ration of solvent mixture__________________________________ 212 

Preparation of chromatograms__________________________________ 212 

Preparation of standards_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 213 

Estimation of uranium_________________________________________ 213 

D~cus~on________________________________________________________ 213 

Effectiveness of s:unple solution_________________________________ 213 

lnterferi ng ions____________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 214 

Optimum drying of sample aliquots on the paper__________________ 215 

Solvent mixture used for separation of uranium ________ . _ _ _ _ _ _ _ _ _ _ 216 

H.esuUs___________________________________________________________ 217 

Literature cited___________________________________________________ 220 

ILLUSTRATIONS 

}i'IOURl~ 29. Standard series of uranium chromatograms on a sheet of 

C. IL L./1 What.man paper____________________________ 213 

30. Variation of standard deviation with umuium content_______ 217 

TABLES 

TABr.,E -1. The effect OIL interfering ions by the addition of Al(N03) 3 to 

nitric acid_____________________________________________ 214 

2. Comparison of estimation of uranium in phosphate rocks by 

chromatographic and fluorimetric methods_________________ 215 

3. Comparison of quality of chromatograms obtained on a 0.05-ml 

aliquot at 73° F after various periods of drying____________ 216 

4. Mean and standard deviation of duplicate uranium determinations__________________________________________________ 218 

5. Comparison of uranium in crystalline rocks by chromatographic 

and fluorimetric estimation methods _____ ~-_______________ · 218 

6. Comparison of uranium in sedimentary rocks by chromatographic and fluorlmetric methods of estimation_____________ 219 

III 
A CONTRIBUTION TO GEOCHEMISTRY 

A FIELD CHROMATOGRAPHIC METHOD FOR DETERMINATION OF URANIUM IN SOILS AND ROCKS 

By 0HAHLl!:S E. THOMPSON and H. vV. l.u\KIN 

ABSTRAC'J.' 

A simple and mpid field method for the ~emiquantita.tive determination of 

urn,nium in soils and rocks was needed to supplement the Geiger and scintillation 

counter techniques now used extensively in prospecting for uranium. In the 

proposed method n.n aliquot of a nitric acid-aluminum nitrate solution of the 

sample is plficed 011 n, specinJ paper, n.nd the uranium is separated from the other 

sn,mplc constituents by the upward flow of a solvent mixture through the paper. 

The suggested procedttre is n.pplicn.ble to samples contn.ining 4 to 1,200 ppm of 

uranium, and with a slight modificatiou it can be used for samples containing 

larger amounts. 

By moans of tho propo~ed method relatively unskilled workers can use inexpensive n,nd easily obtn,inablo reagent:'3 and equipment to determine uranium in 

the field in at least 60 samples of soils and sedimentary rocks ground to 100 mesh 

during an eight hour day. 

INTltODUC'".rJON 

Although the first use of chr01natographic techniques was in the 

separation of organic compounds, the development of partition cluomatography using efficient ion-exchange resins and methods of filter paper 

chr01natography has Inade chromatographic techniques very useful in 

inorganic research and analysis. ~1any of these procedures have been 

c01npiled by Pollard and ~t[c0Inie (1953) and Smith (1953). It is 

possible to separate closely related elements such as tantalun1 and 

niobium; cht·o1natographic methods have been developed for the 

separation and quantitative estin1ation of these elmnents. 

The requirements for paper cht·on1atographic techniques are: (1) a 

solution of the ions to be separated, (2) a strip of paper OL' colun1n of 

cellulose to support the solution aliquot; the filter paper strips are 

used for 1nicro mnoun ts; the cohunn of cellulose for n1acro amounts, 

(3) a solvent to effect the separation of ions in the paper, and (4) a 

color-producing reagent to indicate the position and relative mnounts 

of the ions separated. 

209 
210 CONTRIBUTIONS TO GEOCHEMISTRY 

The possibilities of rapid and inexpensive chromatographic methods 

useful in geochemical prospecting were explored by Hunt, North, and 

Wells (1955). l\1ost chromatographic techniques are time consuming 

and the- necessary apparatus is bulky. However, these authors 

described rapid methods requiring little apparatus for the detennination of uranium, lead, copper, cobalt, and nickel in soils and rocks. 

The method described herein is an improvement of the Hunt, North, 

and Wells paper chromatographic procedure for uranium. The 

interference of chloride, fluoride, sulfate, and phosphate ions has been 

greatly reduced, and serious difficulties clue to variation of the salt 

content of the sample solutim1 I-lave been eliminated. Also, standard 

conditions for drying the paper have been established which permits 

the use of the method in any climate. 

The authors are grateful for the assistance given them by L. B. Riley 

in the statistical study of the results obtained by the n1ethod. 

REAGENTS AND APPARATUS 

All reagents used are of analytical grade. 

Nitric acid, concentrated. 

Nitric acid-aluminum nitrate solution. To 1 part concentrated nitric acid and 

3 parts water, add aluminum nitrate until a few crystals remain undissolved 

two hours after the last addition. 

Standard uranium solution, 0.1 percent. 

Dissolve 0.295 gram of U30s in 65 ml of concentrated nitric acid, transfer the 

solution to a 250-ml volumetric flask, add 100 ml of water, add aluminum 

nitrate until a few crystals remain undissolved and dilute to volume with water. 

Dilute standard uranium solutions, used in preparation of standard uranium 

chromatograms. Pipet the appropriate volume, given below, of the standard 

0.1 percent uranium solution into 10-ml volumetric flasks containing 3 ml of 

nitric acid-aluminum nitrate solution, and finally dilute to the 10-ml mark with 

the nitric acid-aluminum nitrate solution. 

Volume of standarcl 0.1 percent uranium solution 

required 

Milliliter 

0. 1 

.2 

.4 

.8 

I. 5 

3 

6 

Ethyl acetate. 

Aluminum nitrate, crystalline. 

Hydrofluoric acid, 48 percent. 

Uranium content of dilute solutions 

Percent Micrograms 

JJer ml 

0. 001 10 . 002 20 . 004 40 . 008 80 . 015 150 . 03 300 . 06 600 

Potassium ferrocyanide solution, 5 percent, aqueous. 

Calcium chloride (anhydrous). 
ME'l'HOD FOH DE1'ERMINATION OF UHANIUM IN SOILS AND ROCKS 211 

WhaLman C.R.L./1 chromatographic p·aper. 

Culture tubes, Hi x 125 mm, borosilicate glass. 

Test tube rack, capacity 40 tubes. 

Cylinders, graduated, 50 ml and 10 ml. 

Balance, sensitivity 2 mg. 

Beakers, 600 ml. 

Dishes, platinum, 50 ml. 

Dishes, porcelain, 50 ml. 

Stirring rod, plastic. 

\Vatch glasses, 125-mm diameter. 

Indicator spray bottle or atomizer. 

Flasks, volumetric, 250 and 10 ml. 

Pipets, serological, 0.1 and 1 ml, graduated. 

Pipets, volumetric, 1 and 2 ml. 

Pipets, micro, 0.01 and 0.05 ml. 1 

Stove, gasoline, portable 

Water bath 

Desiceator, inside diameter 150 mm. 

PROCEDURE 

PREPARATION OF SAMPLE SOLUTION 

Sedimentm·y 1'ocks.-Weigh 1 g of finely powdered soil or rock sainple and transfer to a 16 x 125 mn1 culture tube (0.1 g can be used for 

smnples containing more than 1,200 ppn1). Add 2 ml of nitric acidnlmninmn nitrate solution and digest the sample for one hour in a 

boiling water bath. Allow the insoluble residue to settle. (Alternatively the sainple solutions n1ay be centrifuged for three minutes 

at 1,500 rp1n to obtain a clear aliquot.) 

Soils and materials containing .large amounts of organic matter.-

'Veigh 1 g of finely powdered soil or rock sample, transfer to a porcelain dish, and ignite for 15 minutes over a gasoline stove. 1'ransfer 

·the ignited san1ple to a culture tube, add 2 ml of nitric acid-aluminum 

11itrate solution, and digest the sample for one hour in a boiling water 

bath. Allow the insoluble res!dtie to settle. 

Crystalline rocks.-vVeigh 1 g of finely powdered sample and transfer 

it to ft. pla.Limun dish. Add about 10 ml of hydrofluoric acid and 3 ml 

of concentrated nitric 'acid, and ~tir to effect contact of the acids with 

tbe snn1ple. Let stand 4 hours ~t roon1 temperature, and then evaporate the contents of the dish to dryness on a hot water bath. Transfer the contents of the dish to a culture tube using a plastic stirring 

rod; add 2 ml of nitric acid-aluminun1 nitrate solution to the dish, 

swirl, and transfer this wash solution to the culture tube. Digest the 

solution in the culture tube for one hour in a boiling water bath. 

Allow the insoluble residue to settle. 

I M ici'Opipcts convenient for removing small aliquots of sample solution from the digestion tubes may be 

made us follows: Draw one end of 3-mm outside-diameter glass tubing into a capillary. To calibrate the 

micropipet, place the orifice of a standard 0.1-ml pipet, graduated in O.Ql ml, next to the fine capillary tip of 

the micropipet and allow thP desired volume to enter the micropipet by capillary flow. Then mark the 

micropipet at the meniscus with a small file. Repeat to assure accuracy. Suitable micropipets are also 

commercially available, 
212 CON'l'RIBUTIONS TO- GEOCHEMISTRY 

PREPARATION OF SOLVENT MIXTURE 

. Transfer 30 n1l of ethyl acetate, 3.5 ml concentrated nitric acid, 

and 10 ml of water into a 600-ml beaker. Cover the beaker with a 

125-mm diameter watch glass and allow the solvent mixture to stand 

in the beaker 20 minutes before using. 

PREPARATION OF CHROMATOGRAMS 

Withdraw an appropriate aliquot of the supernatant sample 

solution with a micropipet and spread the aliquot evenly starting 

abotit 1.5 cn1 frmn the bottom of one of the strips on a piece of 

vVhatman C. R. L./1 filter paper (fig. 29), and placing 10 sample 

aliquots of equal volume on each sheet. For sa1nples containing 4 to 

240 ppm uranium, use a 0.05-ml aliquot. For samples containing 

240 to 1,200 ppn1 uranium, use a 0.01-ml aliquot of the san1ple solution. Use only. one size of aliquot on each sheet of paper. Fasten 

the top corners (A and B in fig. 29) together with a paper clip to 

form a cylinder and place upright in a desiccator (with an inside 

diameter of 150 mm) containing dry calciun1 chloride for the time 

specified in tliC following tabulation chart. 2 

Drying time 'Temperature (

0 Ji') Aliqnot size (rnl) (minutes) 

<60 0. 05 20 

60-90 . 05 10 

>90 . 05 8 

<60 . 01 12 

60-90 . Ol 8 

>90 . 01 5 

After the aliquots have dried, place the paper cylinder upright in 

the 600-ml beaker containing the solvent mixture. Cover the beaker 

with a watch glass. Leave the paper cylinder in the beaker until the 

solvent front rises 8 em above the bottom of the paper. The solvent 

front must rise 2 em above the area wetted by the sample aliquot but 

should not rise above the top of the slit. Remove the paper from the 

beaker, unfold, and place it on a clean surface. 

Allow the ethyl ac_etate to evaporate, then spray the chromatogran1 

with a 5 percent aqueous solution of potassium ferrocyanide. If 

uranium is present a ferrocyanide complex of uranium forms a brown 

stain at the highest point the solvent had risen. 

2 In connection with the development of a method for determining uranium in natural water, F. N. Ward 

and A. P. Marranzino of the Geological Survey have recently found that drying the paper in a desiccator 

containing a saturated solution of magnesium nitrate in contact with an excess of the salt provides a proper 

humidity for this operation. A paper may be left in the desiccator of the size described above for 20 minutes 

and be sufficiently dry for the development of a good chromatogram. Leaving the paper in the desiccator 

overnight does not change the results. The new desiccant is recommended to replace the one described here. 
~lETHOD FOH DETER~IIXATIOX OF rRAi\TC~l IX :-;OILS AXD ROCI\S 213 

A B 

Fu t H E 2fl. Standard ~<·rif'~ of uranium chromatop:rams on a siH'd of C. H . L ./1 

\Yhatrnan paprr 

PREPARATION OF STANDARDS 

Pn.'p<ll'<' n serips of stnndanls containing 0.1, 0.2, 0.4, 0.8, 1.6. ;L 

and G mierognuns of unlllium on a shel't of C. R. L./1 \Yhalm<lll 

pnper ns follo,,·s: Plnrt• a 0.01-ml aliquot of rnth of the standard 

uranium solution containing 10, 20, 40, RO, 1<30, :~00, and GOO micrograms of uranium per ml on 7 strips of a sheet of C. R. L. / 1 \Vhntmnn 

pnpPr. Proc<'<'d as din•dcd for sample solutions. 

ESTIMATION OF URANIUM 

( 'omp<U'<' the brown stain of tlw uranium complex obtained from 

the sampll' aliquot ·with standards prepared ut the snnw time, and 

l'l'COl'd tht• llUJnbt•r of micrograms found in the snmplt' aliquot. 'Cse 

tlw following NJuntion to <"t~l<'ulnt<• parts JWr million uranium in tlH• 

nmplc : 

Total Yol. of sample solution J . 

T • /' llll('l'()OTHll1S "t. of sampk X vol. of nhquot o 

found - l T ppm 

DIHCT"SHIOX 

EFFECTIVENESS OF SAMPLE SOLUTION 

'l'hl' pnJH'l' chroma tographie met bod of st•parn tion and estimation 

of uranium n'quirrs that tlw sampl<' be dissolvrd in 1 :~ nitric acid 

and thnt nltuninum nitl'nte be JH'Psent in tlH• sample solution to prevrnt 

int<•rf('l'('JH'e of phosphatr and othrr anions. Dilut(• nitric Hcidaluminum nitrut(• solution has hePn found to he a very satisfactory 

reagent for di~solving thr urnnium in several hundred sampl('S from 

th e Colorndo Platen11 (tahlr G). Jlowever, this reagent alon<' would 

4:.!2 t 44-57--2 
214 CON'l'RIBUTIONS TO GEOCHEMISTRY 

not extract all of the uranium in a number of igneous rock samples 

(table 5). Fusion witR. fluxes such as potassium bisulfate, potassium 

hydroxide, sodium hydroxide,~r.)ithium,J_l;tyQ.roxide and potassium 

nitrate, sodium carbonate, sodium carbonate and potassium nitrate, 

ammonium fluoride, or combinati~~is of !these proved cumbersome or 

otherwise unsatisfactory. The m~~·t sati~factory attack on this type 

of sample was the hydrofluoric-ni'thc aeid digestion. '· ~~ 

INTERFERING, ~ON~ 

~}.> 

One hunch·ed micrograms of uraniu:(p. were added to duplicate 

samples of salts· of a number of cations ·~pel apions, and one of the 

duplicate mixtures was digested with 1 +3o;J.~itric~.j1cicl and the other 

with nitric acid-aluminum nitrate solution. 'The etf~ct of these ions 

on the recovery of ur~nium is shown in table 1. The cations Ba, Sr, 

Li, Fe (III), Ca, l\1g, K, and N a did not interfere when 100 micrograms of U was added to their nitrates. Where the 1 +3 nitric acid 

acid digestion was used, phosphate, chloride, fluoride, sulfate in sn1all 

amounts, and carbonate in extremely large amounts interfered with 

the separation of uranium. Carbonate is easily recognized by effervescence and can be eliminated by first evaporating the nitric acid 

solution of the sample to dryness and dissolving the residue in nitric 

TABLE 1.-The effect on interfering ions by the addition of Al (N03) 3 to nitric acid 

containing 100 micrograms of uranium 

Salt added (gram'>) 

1 NH4 VOa _____ --------------------------------

1 (NH4)6 Mo1024--------------------------------

1 NaN03--------------------------------------

1 H3BOa---- _---------------------------------- .5 N aHS04-- ________ --------------------------- .2 N aHS04-- _____ ------------------------------ . 1 N aH S 0 4 ___ - _ - _ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

.5 KHS04-- _______ ----------------------------- .2 KHS04-- ______ ------------------------------ .1 KHS04-- ______ ------------------------------ .5 NaCl ______________________________________ _ .2 NaCl ______________________________________ _ .1 NaCl ______________________________________ _ .5 NH4F ______________________________________ _ .2 NH4F ______________________________________ _ .1 NH4F ______________________________________ _ 

.5 N a2HP04 _____________ ----------------------- .2 Na2HP04 __________ - -------------------------

.1 N a2HP04. ___ -------------------------------- 1 N a2C03-- __ ---------------------------------- . 5 N a2C03- - _ - - - - ----- - -- ------- -- - - -- - - -- - ---- .2 Na2C03-------------------------------------

Uranium found (micrograms) 

1+3 HNOa HNOa·Al (NOah digestion digestion 

-100 100 

100 100 

100 100 

100 100 

0 12 

12 30 

24 60 

0 0 

0 30 

12 60 

0 30 

0 60 

0 100 

0 30 

0 60 

12 100 

0 100 

0 100 

0 100 

0 0 

0 100 

100 100 
ME'l'HOD FOH. DETERMINA'l'ION OF URANIUM IN SOILS AND ROCKS 215 

ucid. However, with the Al (N03)3 present it was not necessary to 

take to dryness and redissolve. The interference of phosphate is 

eli1ninated, and interference of the other anions is reduced substantially by the· use of the nitric acid-alumimun nitrate solution for 

digestion of the sample. 

To test further the effect of almnimun nitrate on the interference 

of phosphate, 20 smnples containing as much as 35 percent phosphate 

(P04- 3

) were analyzed, once by digesting with just 1 +3 nitric acid, 

and a second ti1ne by digesting them with 1 +3 nitric acid saturated 

with aluminmn nitrate. Less than 4 ppn1 of uranium was found 

when 1+3 nitric acid was used alone. However, when these san1ples 

were digested with nitric acid-ahunitnun nitrate solution and the 

uranimn estin1ated chromatographically, the results compared favorably with. those obtained by fluorimetric estimation as shown in 

table 2. 

TABLE 2.-Comparison of estimation of umni'l.on in phosphctte 1·ocks by chromato-

(Jmpldc and jluorimetric methods 

Uranium by chromatographic estimation 

Sample no. (ppm) after 

nitric acidaluminum ni- trate dige~tion 

54-4i:3________________________________________ 160 

54-46S________________________________________ 100 

54-5:39________________________________________ so 

54-464________________________________________ so 

54-472________________________________________ 120 54-47() _________________________ j______________ 60 

54-4SO________________________________________ so 

54-4~)5_-------- ------------------------------- 120 54-46()________________________________________ 60 

54-475________________________________________ 60 

54-494________________________________________ so 

54-504________________________________________ 30 

54-533________________________________________ 25 

54-492________________________________________ 25 

54-40()________________________________________ 40 

54-515________________________________________ 25 

54-516________________________________________ 25 

54-544________________________________________ 10 

54-54()________________________________________ 15 

54-620________________________________________ 15 

Uranium by 

fiuorimetric 

estimation 

(ppm) after 

nitric acid 

digestion 

140 

120 

120 

90 

90 

90 

90 

90 

70 

70 

60 

50 

40 

30 

30 

20 

20 

20 

20 

20 

OPTIMUM DRYING OF SAMPLE ALIQUOTS ON THE PAPER 

1'here is an optilnmn moisture content of the paper wet by the 

aliquot at which the uranimn n1oves in the best tight band in the 

solvent front. If the paper is too moist, the uraniun1 trails behind 

the solvent front; and if too dry, the uranimn either does not n1ove or 

1noves slowly. Jron Inoves n1ore rapidly the drier the spot, conse-
216 CONTRIBUTIONS TO GEOCHEMISTRY 

quently excessive drying after addition of the aliquoL to the paper 

results in the uranium being concealed in the wide blue band of the 

iron ferrocyanide complex. 

It was observed that the optimum drying time for paper containing 

aliquots of 1 +3 nitric acid digestions of samples varied appreciably 

between samples. 'fhe variation in optimum drying time that was 

observed is attributed by the authors to the lowering of the vapor 

pressure of the sample aliquot by the soluble salts occurring in the 

samples. In any event, the addition of a constant large mnount of a 

salt (aluminum nitrate) to every sample overshadows the relatively 

small variations between samples and makes it possible to give a 

specific drying ti1ne for a given humidity and temperature. The data 

presented in table 3 illustrate that the digestion of the sample with 

(1 +3) nitric acid saturated with aluminum nitrate results in a sa1nple 

aliquot of sufficiently uniform salt content to permit prediction of 

optimum drying time. The optimum drying time for an 0.05-ml 

aliquot in a desiccator with an inside diameter of 150 mm containing 

anhydrous OaOlz is 10 minutes at 73° F (22.8° 0). The optimun1 

drying times for various temperatures and aliquots given on the chart 

in the procedure were similarly obtained. 

TABLE 3.-Comparison of q1wlity of chromatogmms obtained on a 0.05 ml aliquot at 

73° F after various periods of drying. (Desiccator containing CaCl2) 

[N =No band, D=Difficult to estimate, F=Fair band, G=Good band] 

Material ______________________________ _ 

1 +3 nitric acid 

Phosphate rock_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ N 

Sandstone______________________________ F 

Soil ______ .:._____________________________ ]) 

D1 ying time, minntes 

5 1 10 1 15 1 20 

N 

F 

F 

N 

F 

F 

N 

F 

D 

1+3 nitric acid-aluminum nitrate solution 

Phosphate rock_________________________ D 

Sandstone______________________________ F 

SoiL___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ D 

G 

G 

G 

F 

F 

F 

D 

D 

D 

SOLVENT MIXTURE USED FOR SEPARATION OF URANIUM 

N 

F 

D 

D 

D 

D 

30 

The relative proportions of ethyl acetate, water, and concentrated 

nitric acid affect the movement of the uranium in the solvent front. 

Use of 35 ml of ethyl acetate, 10 ml of water, and 3.5 ml of concentrated nitric acid resulted in the best movement of the uranium with 

the solvent front. If these proportions are changed n1aterially, the 
ME'l'HOD FOH DE'L'EHMlNA'l'ION OF UHANlUM IN SOILS AND ROCKS 217 

um.nimn is Hot concentrated in the solvent front but is spread along 

the length of the strip. It has been found that this solvent mixture, 

because of changes in composition, is satisfactory for a maxi1nun1 of 

about three hours only or for five sheets of paper, whichever is first. 

RESUL~rs 

The precision of the proposed method was csti1nated by a statistical 

study of 97 pairs of duplicate determinations on 97 different materials 

ranging in uraniun1 content frOin 4 to 1,000 pp1n. 1'hcsc samples 

were analyzed in eight groups according to their apparent uranium 

content with no less than 10 samples in each group. The n1ean and 

standard deviation of each group were calculated by the procedure 

described by Youdcn (1951, p. 17). These data arc given in table 4. 

The n1ean values were then plotted against the standard deviation 

(fig. 30) and a straight line relationship obtained. Using the equation 

for a straight line SD=a+ b x where SD equals estimated standard 

deviation and xis the quantity of uraniun1 found in ppm, we obtained 

SD=O+O.l3 x or SD=0.13 x for values ranging frOin 6 to 900 ppm. 

z 75 0 

i= 

< 

> 

LLI 

0 

0 

a: 

< 0 50 z 

<( 

..... 

en 

25 

2 3 4 500 6 7 8 9 1000 

MEAN 

URANIUM, IN PARTS PER MILLION 

FruGRE 30. Variation of standard deviation with uranium content. 
218 CONTRIBUTIONS TO GEOCHEMISTRY 

TABLE 4.-1l1ean and standard deviation of d'uplicate uranium determinations 

Range of uranium content in groups of samples (ppm) 

4-12 ___________________________________ _ 12-30 __________________________________ _ 30-60 __________________________________ _ 60-100 _________________________________ _ 100-200 ________________________________ _ 200-400 ________________________________ _ 40Q-600 ________________________________ _ 800-1000 _______________________________ _ 

No. of pairs of duplicate determmations 

12 

11 

12 

11 

16 

11 

10 

15 

Mean (ppm) 

6. 8 

20. 7 

42 

81 

150 

332 

567 

887 

Standard 

deviatiOn 

(ppm) 

1.7 

3. 3 

6. 7 

10.9 

20. 9 

42.6 

71. 5 

112. 6 

Thus we find that the estimated standard deviation for the method 

is 13 percent of the value obtained and, assuming normal distribution 

of values about their mean, that about 1 out of 20 replicate determinations will differ by more than 26 percent of the value obtained. This 

is adequate precision for a rapid semiquantitative field method suitable 

for geochemical exploration. 

Data presented in table 5 illustrate the accuracy of results obta.ined 

by the proposed procedure for crystalline rocks. The figures obtained 

by the paper chron1atographic procedure a.re given in the third 

column; the fourth and fifth columns show the range of plus and 

minus two standard deviations for this method. 

TABLE 5.--Comparison of uranium in crystalline rocks by chromatographic and 

jluorimetric estimation methods 

Uranium Uranium 

found by Calculated 95 percent found by 

Sample no. Type of material chroma to- confidence limits 1 fluorimetric 

grapbtc (ppm) estimation 

estimation (ppm) (ppm) 

-

54-4597 ______ Hornblende syenite ______ 4 (2) (2) 6. 6 

54-4598 ______ Bostonite (sodic) ________ 4 (2) (2) 6. 7 

54-4599 ______ Quartz monzonite _______ 4 (2) (2) 8. 2 

54-4600 ______ Quartz monzonite _______ 8 6 10 10. 0 

54-4601 ______ Bostonite (potassic) ______ 16 12 20 13. 8 

54-4602 ______ Bostonite _______________ 16 12 20 17. 6 

54-4603 ______ Sodic granite ____________ 16 12 20 18. 1 

54-4604 ______ Bostonite (potassic) ______ 16 12 20 18. 9 

54-4605 ______ Quarts monzonite (sodic)_ 16 12 20 19. 4 

54-4606 ______ Bostonite (sodic) ________ 16 12 20 21. 7 

54-4607 ______ Bostonite (potassic) ______ 24 18 30 32.5 

54-4608 ______ Bostonite (sodic) ________ 30 22 38 38. 3 

54-4609 ______ Bostonite (potassic) ______ 30 22 38 41. 9 

54-4610 ______ Bostonite (potassic) ______ 40 30 50 46. 9 

54-461 L _____ Bostonite (potassic) ______ 40 30 50 57.8 

54-4612 ______ Bostonite (potassic) ______ 60 44 76 69.8 

54-4613 ______ Bostonite (potassic) ______ 120 88 152 138. 6 

t 95 percent confidence limits based on calcul~tions from data presented in table 4. 2 These samples are outside the range of data on which confidence limits were calculated. 
ME'l'HOD FOR DETERMINATION OF URANIUM IN SOILS AND ROCKS 219 

The fluorin1ctric results (last colmnn). are consistently higher than 

those obtained by the proposed procedure. The low values given by 

the paper chromatographic procedure arc probably due to incomplete 

solution of the san1ple as the proposed attack of the sample with 

hydro'fluoric and nitric acid fails to decompose many refractory 

minerals such as zircon. However, the results by the paper chroInatographic procedure increase in the same order as the results 

obtained by c01nplcte solution. 

TABr ... l<J 6.-Comparison of urani'u,m in sedimentary rocks (other than phosphates) 

by chromatogmphic a'nd jl'llori1netric methods of estimation 

,,. 

Sample no. 

"' 

72772 211~0~----------------------- _______________________ _ 

70256 72491~----------------------- _______________________ _ 70258 _______________________ _ 72490 _______________________ _ D-92411 _____________________ _ 

211105----------------------- ])-79695 _____________________ _ 70254 _______________________ _ 72227 _______________________ _ J)-91018 _____________________ _ 72773 _______________________ _ 1)-79711 _____________________ _ 

71505 ])-79705 _______________________ ---------------------_ 211102 ______________________ _ 72866 _______________________ _ 211103 ______________________ _ 2L1099 ______________________ _ 2L1094 ______________________ _ 211093 ______________________ _ J)-91095 _____________________ _ 211095 ______________________ _ 2L1109 ______________________ _ ])-91016 _____________________ _ ])-91012 _____________________ _ 211110 ______________________ _ 2L1108 ______________________ _ 2L1106 ______________________ _ 211111 ______________________ _ 211107 ______________________ _ 2L1101 ______________________ _ 211097 ______________________ _ 211096 ______________________ _ 211100 ______________________ _ ])-91011 _____________________ _ ])-91012 _____________________ _ 211098 ______________________ _ 

Uranium 

found by chromatographic 

estimation 

(ppm) 

20 

20 

20 

30 

30 

30 

30 

40 

40 

40 

40 

50 

60 

60 

60 

80 

100 

100 

100 

100 

JOO 

150 

300 

300 

500 

800 

900 

1000 

1500 

1500 

2000 

2000 

3000 

3000 

3000 

3500 

4000 

6000 

9000 

Calculated 95 percent confidenre limits I 

(ppm) 

(~) 

(~) 

(2) 

(2) 

(2) 

(2) 

(2) 

(2) 

(2) 

(2) 

(2) 

(2) 

15 

15 

15 

22 

22 

22 

22 

30 

30 

30 

30 

37 

44 

44 

44 

60 

74 

74 

74 

74 

74 

112 

220 

220 

370 

600 

700 

25 

25 

25 

38 

38 

38 

38 

50 

50 

50 

50 

66 

76 

76 

76 

100 

126 

126 

126 

126 

126 

188 

380 

380 

630 

1000 

1100 

(2) 

(2) 

(2) 

(2) 

(2) 

(2) 

(2) 

(2) 

(2) 

(2) 

(~) 

(2) 

• 95 percent confidence limits based on calcul:ltions from data presented in table 4. 2 'l'hcsc samples arc outside the range of data on which confidence limits were calculated. 

Uranium 

found by fluorimetric 

estimation 

(ppm) 

20 

20 

30 

20 

30 

40 

40 

30 

30 

40 

50 

50 

40 

50 

60 

40 

90 

60 

100 

90 

120 

110 

310 

270 

500 

720 

800 

1000 

1500 

1500 

2000 

2000 

1500 

4000 

3400 

1700 

4800 

6000 

6100 
220 CON:l'RIBUTIONS TQ GEOCHEMISTRY 

Thirty-nine smnplcs of sedimentary rocks low in phosphate were 

run independently by the fluoromctric and chromatographic Incthods 

(table 6). The upper and lower value for the 95 percent level of 

precision for the paper chron1atographic method are given in the 

third and fourth columns and only two of the fluormnctric values 

arc substantially outside of these ranges. Assuming that the :fluormnctric values arc correct, the accuracy of the proposed Incthocl 

for sedimentary rocks is approximately the same as the precision 

of the method. 

'I'he Inethod is fast and simple enough to enable a relatively unskilled worker to determine the uranium content in 60 or n1ore samples 

in the field in an 8-hour day. In this laboratory a chemist has 

determined uranium content chromatographically in as Inany as 120 

san1plcs in an 8-hour day. The method permits the estimation of as 

little as 4 parts per million of uranium and as much as 1,200 ppm 

without n1odification. Larger uranium contents can be determined 

by simple modifications. 

LITERATURE CITED 

Hunt, E. C., North, F. A., and Wells, R. A., 1955, Application of paper chromatographic methods of analysis to geochemical prospecting: The Analyst, 

v. 80, p. 179-194. 

Pollard, F. H., and McOmie, J. F. W., 1953, Chromatographic methods of 

inorganic analysis, New York, Academic Press, Inc., 192 p. 

Smith, Orsino C., 1953, Inorganic chromatography, New York, D. Van Nostrand 

Co., Inc., 134 p. 

Youden, vV. G., 1951, Statistical methods for chemists, New York, John Wiley 

and Sons, Inc., 126 p. 

U, S. GOVERNMENT PRINTING OFFICE 1957