GEOLOGICAL SURVEY CIRCULAR 199

U. S. GEOLOGICAL SURVEY 

FLUORIMETRIC METHODS 

OF URANIUM ANALYSIS

By F. S. Grimaldi, Irving May, and M. H. Fletcher

UNITED STATES DEPARTMENT OF THE INTERIOR 

Oscar L. Chapman, Secretary

GEOLOGICAL SURVEY 

W. E. Wrather, Director

GEOLOGICAL SURVEY CIRCULAR 199

S. GEOLOGICAL SURVEY FLUORIMETRIC METHODS OF URANIUM ANALYSIS

By F. S. Grimaldi, Irving May, and M. H. Fletcher

This report concerns work done on behalf of the 

U. 8. Atomic Energy Commission and is published 

with the permission of the Commission.

Washington, D. C., 1952

Free on application to the Geological Survey, Washington 26, D. C.
PREFACE

This manual was written to serve as a guide for-analysts interested in the determination of small amounts of uranium (Assayers 

Guide, 1949; Rodden, 1950). All the methods presented here have 

been developed in the U. S. Geological Survey and are based on the 

measurement of the fluorescence of uranium in fluoride melts. These 

methods have been used for the analysis of almost every material 

thought to contain uranium.

The manual presents a general discussion of the fluorimetric 

method of analysis for uranium, detailed procedures for the analysis of representative materials, and shop drawings of the fluorimeters used in the Survey.

The methods and instruments described here were completed 

as part of a program undertaken by the Geological Survey on behalf 

of the Division of Raw Materials of the U. S. Atomic Energy 

Commission.
CONTENTS

Page

Introduction .................................. 1

General discussion of reagents and

apparatus .................................. 1

Mixed carbonate -fluoride flux............. 1

Containers.............................. 1

Fluorimeters............................ 2

Ultraviolet light source.............. 2

Filters ............................ 2

Detection of fluorescence and 

measurement of photoelectric 

currents......................... 2

Types of fluorimeters............... 2

General discussion of procedures............... 3

Preparation of melts..................... 3

Direct fluorimetric or "dilution" method ... 3 

Extraction-fluorimetric method ........... 3

Carbonate-fluorimetric method ........... 4

Accuracy of the fluorescence method....... 4

Detailed procedures........................... 4

Direct fluorimetric method

or "dilution" method ................... 4

Range ............................. 4

Application......................... 4

Preparation of solution 

for analysis...................... 5

Phosphate rocks............... 5

Silicate and carbonate rocks .... 5

Refractory materials .......... 5

Fluorimeters ...................... 5

Example: Determination of uranium 

in Florida phosphates using "large" 

samples ......................... 5

Extraction-fluorimetric method ........... 5

Range ............................. 5

Application ........................ 5

Preparation of solution

for analysis...................... 5

Page

Detailed procedures--Continued

Extraction-fluorimetric method Continued 

Preparation of solution for 

analysis--Continued

Phosphate rock................ 5

Silicate and carbonate rocks.... 5

Refractory materials .......... 5

Fluorimeters....................... 6

Examples: 1. Determination of 

uranium in shales after extraction 

of uranyl nitrate.................. 6

2. Determination of 

0.00001 percent-uranium in* 

feldspar......................... 6

3. Determination of 10"? 

percent uranium in fresh, saline, 

and sea water ..... .............. 7

Carbonate-fluorimetric method ........... 7

Range ............................ 7

Application......................... 7

Preparation of solution

for analysis ...................... 7

Silicate, carbonate, and

phosphate rocks............. 7

Refractory materials .......... 7

Fluorimeters ...................... 7

Examples: 1. Determination of 

uranium in lignites after alkali 

carbonate separation ............. 7

2. Determination of 

uranium in monazite after alkali 

carbonate separation.............. 8

Details of fluorimeters ........................ 8

Reflection fluorimeter.................... 8

Transmission fluorimeter....... ......... 12

Literature cited.............................. 20

ILLUSTRATIONS

Page

Figure 1.

2.

3.

4.

5.

6.

7.

10.

Platinum dish.............................................................................. 1

Schematic diagram of a "reflection"-type fluorimeter .......................................... 2

Schematic diagram of a transmission-type fluorimeter......................................... 2

Effect of time of heating and temperature of heating on the fluorescence" of a fixed weight

of uranium............................................................................... 3

Expanded details of the modified fluorimeter.................................................. 9

Rear view 'assembly of the modified fluorimeter ............................................... 10

Complete assembly of the modified fluorimeter................................................ 11

A working curve for a "reflection" fluorimeter. ............................................... 12

Fluorimeter assembly (transmission) ........................................................ 13

Fluorimeter -- cut-away and cross-section ..........................;........................ 14

111
ILLUSTRATIONS Continued

Page

Figure 11. Details of parts shown in figure 10 .......................................................... 15

12. Details of parts shown in figure 10 .......................................................... 16

13. Details of parts shown in figure 9 .......................................................... 17

14. Details of construction of shield ............................................................ 18

15. Details of construction of phototube housing type B............................................ 19

16. A working curve for a transmission fluorimeter .............................................. 20

TABLE

Page 

Table 1. Quenching data on elements for 2 g of flux. ................................................... 4
U. S. GEOLOGICAL SURVEY FLUORIMETRIC METHODS OF URANIUM ANALYSIS

INTRODUCTION

"Melts obtained by fusing uranium salts with 

sodium fluoride fluoresce a brilliant yellow green 

when exposed to ultraviolet light (Nichols and Slattery, 

.1926). ^The intensity of the fluorescence is proportional, within wide limits, to the amount of uranium 

present, and this relationship is the basis for the 

quantitative fluorimetric determination gf uranium.

The fluorescence test for uranium in specific 

when the excitation is with long wavelength (3650 A) 

ultraviolet light. Niobium fluoresces only weakly when 

exposed to short wavelength light -(2536 A). In spite 

of this specificity, many elements may interfere by 

quenching the uranium fluorescence. For example, 

a few micrograms of Co, Cr, Ni, or Mn will reduce 

the fluorescence of uranium by more than 10 percent.

The uranium fluorescence may be enhanced by 

minute amounts of other elements which by themselves 

do not fluoresce in fluoride phosphors. This effect 

is seldom encountered in practice. Jacobs (1950) has 

shown that this enhancement is frequently instrumental 

and results from a shift in the spectrum of the emitted 

light to a region generating a greater response from 

the phototube. Depending upon the particular combination of filters and phototube used, this shift in the 

spectrum may appear as enhancement or quenching. 

In some cases the opposing effect of increased phototube sensitivity and decreased transmission by the 

filter will be balanced, and no change will be apparent.

Two techniques are commonly used to reduce or 

to eliminate interference due to quenching. One technique, called the "dilution" method (or direct method) 

involves no chemical separations. It originated with 

Price and others (1945), who found that it is possible 

to reduce quenching to a negligible factor by using 

sufficiently small samples for analysis. The degree 

of quenching depends only on the concentration of the 

quencher in the flux, and not on the ratio of concentration of quencher to concentration of uranium.

In the second technique the uranium is separated 

from quenching elements before the fluoride phosphor is 

prepared. In one type of procedure uranium may be 

freed from quenching elements by precipitating them with 

alkali carbonate solution; the uranium remains in solution as a complex carbonate. Alternately, the separation may be accomplished by extraction of uranyl 

nitrate by organic solvents. The latter procedure is 

also very useful for the concentration of uranium.

GENERAL DISCUSSION OF REAGENTS 

AND APPARATUS

Mixed carbonate-fluoride flux

Although sodium fluoride is still used for the 

preparation of the uranium phosphors, it has been replaced largely by other fluxes having more desirable 

properties. Ideally a flux should give high sensitivity 

and have desirable physical characteristics. It is difficult to work with sodium fluoride because of its high 

melting point and its tendency to stick to platinum and 

gold containers. The attack on platinum and gold containers is also more serious at elevated temperatures,

^See literature cited.

resulting in some quenching of the uranium fluorescence by the dissolved metal. We employ a mixture 

of 9 parts by weightNaF, 45.5 parts by weight Na2CO3, 

and 45.5 parts by weight K>>CO3. This flux melts at 

about 605 C, does not stick to platinum vessels, produces mechanically strong melts which develop no 

cracks, and gives about the same sensitivity as pure 

NaF. Melts prepared from this flux deliquesce under 

high humidity but keep for short periods when stored 

in a desiccator.

For the measurement of fluorescence obtained 

from less than 10~8 g of uranium, a flux that yields 

reproducible blanks at a high instrumental sensitivity 

is necessary. This flux is prepared by fusing together 

in platinum the three components in 100-g batches, 

combining and crushing the melts to -5 mesh, and 

ball-milling to about-65 mesh. We call this the "fused 

flux" in the procedures in this report. For amounts 

of uranium greater than 10~8gf the instruments are 

used at a lower sensitivity; a sufficiently uniform flux 

is obtained by simple mixing or grinding of the components of the flux in a ball mill (porcelain, with flint 

pebbles). This flux is used unless otherwise stated.

Containers

Either platinum or gold containers may be used 

for the preparation of the standard melts. Platinum 

crucibles or lids from platinum crucibles may be used 

if specially designed containers are not available. 

Figure 1 illustrates the platinum containers used by 

the Geological Survey.

35mmFigure 1. Platinum dish.
Fluorimeters

The main parts of a fluorimeter are:

1. An ultraviolet light source.

2. Primary and secondary filters.

3. A phototube together with an electrical 

system for measuring its response.

Ultraviolet light source

As the source of excitation, long wavelength 

ultraviolet light (3650 A) as produced by General 

Electric EH-4 (now the H 100-E4) and CH-4 (now the 

H 100-C4) high-pressure mercury-vapor lamps, is 

preferable to short wavelength ultraviolet light (2536 A). 

The shorter wavelength ultraviolet light can excite 

interfering fluorescence, such as that of columbium, 

and is also more dangerous to the eyes. The EH-4 

and CH-4 lamps are operated from a constant-voltage 

transformer with built-in ballast, such as the Sola no. 

30,852 for H-4 lamps (superseded by the Sola constant 

wattage transformer no. 301,883).

Filters

The primary filter absorbs visible light from 

the light source without seriously reducing the intensity of the ultraviolet light. Corning filters, nos. 5860, 

5874, 5mm thickness, are satisfactory. The secondary 

filters allow the visible fluorescent light to pass through 

but absorb ultraviolet light. These secondary filters 

may be glass filters, such as either Corning no. 3484 

or no. 3486 used in conjunction with no. 9780. An 

interference filter whose transmission is peaked at 

5550 A may be substituted for the Corning secondary 

filters.

Detection of fluorescence and 

measurement of photoelectric currents

Most fluorimeters use phototubes for detecting 

the fluorescent light and converting it to electrical 

current which is then measured with or without amplification. Some instruments, such as those employing a Fhotovolt Model 512 (superseded by Model 514M) 

electronic photometer, use a simple phototube. Such 

instruments generally use d-c amplifying circuits to amplify the photoelectric currents before they are measured. 

The Photovolt photometer ordinarily contains two scales 

in a ratio of 1:10. The photometer can be purchased 

with intermediate scales; a convenient arrangement 

is four scales in a ratio of 1:2:5:10.

Other fluorimeters use photo multiplier tubes 

such as the RCA 1P21, 931A, or 5819 tubes. These 

tubes amplify the initial photocurrent several hundredthousand times by means of a series of secondaryemission multiplications. The over-all amplification 

obtained can be varied over a wide range by changing the voltage per dynode stage. A d-c amplifier can 

be used with a photo multiplier tube although, for most 

applications in the fluorimetric method for uranium, 

the photoelectric current from the photomultiplier 

tube can be measured directly with a microammeter.

Types of fluorimeters

Fluorimeters used in the determination of 

uranium may be divided into two types, the schematic 

diagrams of which are given in figures 2 and 3.

In the so-called reflection instrument the components 

are generally arranged so that a part of the fluorescent light emerging from the irradiated side of the

Figure 2. Schematic diagram of "reflection "-type

fluorimeter.

melt is measured. In transmission instruments, the 

phototube and ultraviolet lamp are placed on opposite 

sides of the melt so that the fluorescent light which 

is measured emerges from the side opposite to that 

exposed to ultraviolet light. Detailed descriptions of 

one instrument of each type are given under Details of 

fluorimeters.

Primary filter

Sample

Secondary

filter

Shutter

Phototube

Figure 3. --Schematic diagram of a transmission-type 

fluorimeter.
The transmission instrument is capable of 

giving greater sensitivity than the reflection instrument. It is, therefore, the instrument of choice as 

a research tool and is necessary when uranium is to 

be determined in very small samples. When the direct 

method is used on large samples, the melts obtained 

are sometimes stained. In measuring the fluorescence 

of stained melts, we have found that the reflection 

instrument may give more reliable results.

GENERAL DISCUSSION OF PROCEDURES 

Preparation of melts

The proper preparation of the fluorescent melts 

is probably the most important step in the procedure. 

The flux may attack the platinum container and may 

introduce platinum into the melt. The amount of 

platinum so dissolved increases with time and temperature of fusion. In low temperature fusions the 

amount of platinum dissolved can be tolerated, but 

serious quenching of the uranium fluorescence by 

platinum results from fusions made at high temperatures, especially for prolonged periods of heating. 

The time-temperature curves in figure 4 (Fletcher, 

1950) were obtained with furnace heating and illustrate the serious effects of overheating. It can be 

seen from these curves that the fluorescence of a melt 

is almost independent of the time of heating when low 

fusion temperatures are used.

The melts may be prepared either in a furnace 

or over a burner. The procedure for furnace heating 

is to heat for a total time of 10 min at 650 C with 

intermittent agitation of the melt. Heating over a 

burner is done at the lowest temperature at which the 

flux is fluid and for a period of 2 to 4 min from the 

time when the flux melts completely. It is easy to 

maintain the proper temperature in burner heating 

because radiation-of heat to the air from an open dish 

limits the maximum temperature that may be attained 

and because momentary overheating cannot take place 

at too high a temperature.

50

45

I 40

| 35 01

I 30 

« 25

« 20 01

.1 15

1 10

650 C

345 6789 10 II 

Time of heating (minutes)

12 13 14 15

Direct fluorimetric or "dilution" method

The direct fluorimetric method consists of 

taking a small aliquot of an acid solution of the sample, 

evaporating it in a standard platinum or gold container, 

adding the fluoride flux, and preparing the phosphor 

by fusing at a low temperature. The fluorescence of 

the melt is then measured in a fluorimeter.

The size of the aliquot to take in the direct 

method depends on the composition of the material to 

be analyzed. This size may vary from a few micrograms of sample (for materials containing very strong 

quencher's such as chromium or manganese) to a few 

milligrams of sample (for materials with low concentration of quenchers and/or containing relatively mild 

quenchers). Table 1 summarizes the magnitude of 

quenching produced by various elements. In general 

a 0.1-mg sample results in negligible quenching for 

most rock samples; for some materials (phosphate 

rocks) several milligrams of sample usually yields 

little or no quenching. It is always preferable to use 

the maximum size sample that results in no serious 

quenching in order that the level of fluorescence to be 

measured is considerably above that introduced by 

background contamination. When many samples of 

approximately the same composition are to be analyzed, 

it is advantageous to determine the maximum-size 

sample that can be used in the direct method. The 

measurement of very low fluorescence intensity levels 

requires the use of sensitive fluorimeters.

Extraction-fluorimetric method

Figure 4. Effect of time of heating and temperature of 

heating on the fluorescence of a fixed weight of 

uranium.

In the extraction-fluorimetric method the 

uranium is separated from quenchers before preparation of the fluoride phosphoj. This separation usually 

involves the extraction by means of organic solvents 

of uranyl nitrate from nitric acid solution after the 

addition of a salting agent. A portion of the solvent is 

then transferred to the standard container and after 

evaporation of the solvent the phosphor is prepared. 

The fraction of uranyl nitrate extracted depends both 

on the sol vent and on the salting agent used, and for 

this reason a particular procedure may lend itself to 

either batch or continuous extraction. For example, 

with ammonium nitrate as the salting agent and ether 

as the solvent, continuous extraction is recommended. 

The Geological Survey procedure (Grimaldi andLevine, 

1950) uses batch extraction with aluminum nitrate as 

the salting agent and ethyl acetate as the solvent. 

Aluminum nitrate serves also to complex F~, POf, 

and SO4 ions which otherwise seriously hinder the 

extraction of uranium. Aluminum nitrate is also ad- 

. vantageous in that any aluminum extracted does not 

quench the uranium fluorescence. Vanadium and 

quadrivalent cerium, thorium, and zirconium are 

partly extracted. Neither vanadium nor zirconium 

quenches the uranium fluorescence significantly, but 

cerium or thorium quenching may be serious. Interference due to cerium is eliminated when necessary 

by reducing the cerium to the trivalent state before 

extraction. With large concentrations of cerium, it 

is usually necessary to repeat the extraction. Because 

larger samples may be used with the extractionfluorimetric procedure, less sensitive fluorimeters 

may be used; errors due to contamination are less 

serious.
Table 1. Quenching data on elements for 2 g of flux

Be

S3

Sc Cr Mn| jpe"|

Os

Co Ni

Rh Pd

Ir |Pt

JGu

Ag

Au|

Zn| Ga

Cd In

Hg** Tl

Ge o Se

(Sn | Sb Te

|Pbl Bi Po

o

|Ce

Ra Ac JThj

Pr Nd| o

Pa 

o Eu o Tb Dy Ho Er Ttn Yb Lu

Heavy solid lines enclose elements that are strong quenchers (1-10 ;-quench uranium 

fluorescence by 10 percent or more).

Heavy dotted lines enclose elements that are moderate quenchers (10-50 >-quench fluorescence 

by about 10 percent).

Light solid lines enclose elements that are weak quenchers (50-1,000 Y quench fluorescence 

by about 10 percent).

For elements shown but not enclosed there are no data. The transition elements are probably 

moderate to strong quenchers. Elements not shown do not quench the uranium fluorescence.

* Niobium fluoresces only with short-wave excitation (2556 A).

** Mercury has been reported as a strong quencher of uranium fluorescence, but it is volatilized in the preparation of the melt.

Carbonate-fluorimetric method

In the carbonate-fluorimetric method (Guttag 

and Grimaldi, 1951) an aliquot of a sulfuric acid solution of the sample representing 15 mg or less of the 

sample is treated with alkali carbonate solution in 

excess to precipitate quenching elements; the uranium 

remains in solution. After filtration, an aliquot of 

the filtered solution is transferred to a. standard container, the solution is evaporated, and the standard 

melt is prepared as before. Cerium, cobalt, and 

copper may interfere in this procedure. A very 

small amount of cerium and cobalt follow uranium 

because the precipitates formed from sulfate solutions 

tend to pass through the filter. Most materials do 

not contain sufficient cerium to interfere. With suitable modification the procedure may be used even for 

the determination of uranium in monazite. Cobalt is 

quantitatively removed when another element in addition to cobalt is precipitated with alkali carbonate. 

Copper may remain completely in solution yielding an 

intense blue solution. If the amount of copper not 

precipitated is insufficient to yield a blue solution, no 

quenching of the uranium fluorescence results. When 

a blue solution is obtained, a small amount of hyroxylamine is added after the alkali carbonate to precipitate Cu2O and thus remove the interference of this 

element.

The carbonate procedure has been devised to 

accommodate no more than 15 mg of various metal 

oxides and should not be extended without testing to 

determine that no occlusion of uranium occurs in the 

carbonate precipitate for greater quantities of metal 

oxides,

Accuracy of the fluorescence method

With careful work uranium may be determined 

by the fluorescence method with no greater error than 

± 4 percent of the uranium content. Under 

routine conditions, where speed may be important, 

the error generally is greater and may amount to - 8 

to 15 percent of the uranium content. When errors 

occur the results are generally low.

DETAILED PROCEDURES 

Direct fluorimetric method or "dilution" method

Range: 0.001 percent U and more 

Application

The direct method is generally applicable except 

where the ratio of concentration of quenching elements
to concentration of uranium in the sample is exceptionally high. A limiting ratio is of course determined 

by the sensitivity of the fluorimeter, by the element 

that is producing the quenching and its concentration, 

and by the concentration of uranium in the sample. 

These factors determine the maximum possible dilution. Some authors have set the limiting ratio of 

concentration of quenching elements to concentration 

of uranium at 1,000 to 1. This ratio applies to the 

strong quenchers. (See table 1.)

Preparation of the solution 

for analysis

Phosphate rocks. --Simple attack by nitric acid 

which dissolves the uranium.

Silicate and carbonate rocks. (a) Attack by 

HF-HNOs mixture, or (b) fusion with alkali carbonate 

and then solution of the melt in hydrochloric acid plus 

a few drops of alcohol.

Refractory materials, --(a) Fusion in platinum 

with carbonate-borate flux (3 parts Na-gCOs to 1 part 

^26407) followed by solution of the melt in HC1, or 

(b) fusion in platinum with sodium fluoride followed 

by solution of the melt in HC1.

Fluor imeters

Depending on the concentration of uranium in 

the melt, either the reflection or transmission 

fluorimeter may be used to measure the fluorescence. 

When very low levels of fluorescence are to be 

measured, the melts must be prepared with fused fluoride flux described previously in the text.

Example: Determination of uranium in 

Florida phosphates by the direct method 

using "large" samples (Grimaldi and Guttag,

Range. --0.003 percent U and more.

1950)

Procedure. --1. Weigh a 0.150-g sample of 

phosphate rock (-80 mesh) into a dry 125-ml 

Erlenmeyer flask.

2. Add 50-ml of (18 + 82) HNOs from an automatic buret. Cover the flask with a small watch 

glass.

3. Bring the solution to a boil on a hot plate 

and gently boil the solution for an additional 2 min. 

Cool.

4. Transfer a 0.40-ml aliquot of the supernatant solution to the standard platinum container and 

evaporate the solution to dryness on the steam bath. 

Gently ignite to remove free nitric acid or organic 

matter if present.

5. Add 2.0 g of the fluoride flux (9 parts NaF, 

45.5parts Nar,CC>3 and 45.5parts K^COsby weight).

6. Heat' over a burner at a low temperature 

(less than 700 C) until the flux melts. Then heat for 

an additional 2 to 4 min, at the lowest temperature 

at which the flux stays fluid, swirling and agitating 

the flux to insure a uniform melt. Set the dish on 

an asbestos pad to cool and then place in a desiccator 

for about 30 min.

7. Read the relative fluorescence of the melt 

with the reflection fluorimeter.

8. Determine the percentage of uranium by 

reference to a standard curve relating the relative 

fluorescence (scale deflections) of uranium to the 

amount of uranium in a series of standard melts.

Caution: In preparing the melts it is most important that the temperature not exceed 700 C 

(Fletcher, 1950). Overheating will cause low results 

because of the quenching effect of platinum dissolved 

from the container. The deleterious effect of overheating must be emphasized.

Notes: 1. Uranium results obtained on phosphates from the northwestern part of the United States 

by the above method are generally 10 to 15 percent 

too low due possibly to the quenching effect of chromium 

usually present in these samples. More accurate 

results can be obtained if smaller samples are used.

2. The direct method may also be used for the 

determination of uranium in ashes from plants by 

fusing a 5-mg portion of ash with the flux directly in 

the platinum container without preliminary solution 

of the sample.

3. Phosphoric acid byproducts and wastes from 

phosphoric acid plants usually may be analyzed by 

the direct method using 1 mg of sample.

4. For shales and most rocks a 0.1-mg sample 

results in no quenching of the uranium fluorescence.

5. Uranium in monazite may be determined 

directly on sample sizes of a few micrograms.

6. Whereas uranium is normally determined by 

volumetric procedures in uranium ores such as 

carnotite and pitchblende, a rapid although less accurate uranium determination may be made fluorimetrically. Low-grade carnotite ores (about C. Xpercent 

U) are easily handled by the direct method even with 

less sensitive fluorimeters.

Extraction-fluorimetric method

Range: 0.001 percent U and more 

Application

The method is generally applicable except for 

samples"unusually high in thorium and cerium such 

as high-grade ores of these elements. Howevpr, with 

suitable modifications the procedure may be used for 

the determination of uranium in monazite.

Preparation of the solution 

for analysis

Phosphate rock. --Simple attack by nitric acid.

Silicate and carbonate rocks, --(a) Attack by 

HF-HNOs mixture, (b) Alkali carbonate fusion 

followed by solution of the melt in nitric acid.

Refractory materials. --Fusion with either 

NaOH-NaNC3 mixture or with Na2O2 in a porcelain 

crucible followed by solution of the melt in nitric acid. 

Whatever method of solution is used, the aliquot taken 

for extraction should contain approximately 15 percent 

by volume HNO3-

Silica or other hydrolytic precipitates such as 

TiC2 are not filtered off because they have been found 

not to occlude uranium.
Fluorimeters

Either the reflection or transmission fluorimeter 

may be used to determine the fluorescence.

Example 1: Determination of uranium 

in shales after extraction of uranyl 

nitrate -(GrimaLdi and Levine, 1950)

1. Weigh a 0.150-g sample (-80 mesh) into a 

platinum dish. Gently burn off organic matter if 

present.

2. Moisten the sample with a small amount of 

water and add 5-10 ml HF and 10 ml of (1 + 1) HNO3- 

Digest the sample on the steam bath and evaporate 

the solution to dryness.

3. Add 10 ml ( 1 + 1) HNC3 and evaporate the 

solution to dryness. Repeat if insoluble fluorides 

remain.

4. Add 15 ml (1 + 1) HNO3 and digest the 

sample. Transfer the solution to a 50-ml glassstoppered graduated cylinder. Carefully scrub and 

rinse the dish with water adding the washings to the 

graduate.

5. Make to 50 ml with water and mix.

6. Transfer a 5-ml aliquot of the solution to 

a dry 30-ml glass-stoppered test tube containing 

9-1/2 g of A1(N03 )3' 9H2C. The A1(NC3)3" 9^0 

should be free from uranium. (See note 5.) 

Aluminum nitrate available from several of the 

manufacturers of laboratory chemicals has been 

found to be sufficiently pure as purchased.

7. Place the tube in a beaker of hot water until 

the aluminum nitrate dissolves and then mix. Cool 

the solution to room temperature by removing the 

tube from the hot water and placing it in a beaker of 

cold water.

8. Add 10 ml of ethyl acetate by pipet or buret. 

Stopper the tube and shake the mixture for 30 sec. 

Allow the two layers to separate.

9. After several minutes filter about 5 ml of 

the ethyl acetate through a dry paper into a dry test 

tube. The filter paper is conveniently held in place 

by the test tube.

10. Transfer an 0.80-ml aliquot of the filtered 

ethyl acetate to the standard platinum container. 

Place the container on four layers of water-soaked 

absorbent paper in an enameled pan containing about 

1/16 in. of water. Ignite the ethyl acetate by means 

of a lighted splinter and allow the ethyl acetate to burn 

completely.

11. Gently ignite the residue over a burner, 

add 2 g of flux and fuse as previously indicated.

12. Read the relative fluorescence of the melt 

in the reflection or transmission fluorimeter.

Notes: 1. Alternately, the solution of shales 

may be prepared by Na2CC»3 fusion followed by solution of the melt in sufficient nitric acid to give a 

nitric acid concentration of approximately 15 percent 

by volume. Silica or other hydrolytic precipitates 

need not be filtered off as they do not occlude uranium.

2. For phosphate rocks prepare the solution 

by simple boiling with 50 ml of (18 + 82) HNC-3 as 

described under the "direct" method. Use a 5-ml 

aliquot of the solution for extraction.

3. The same general procedure is used for 

determining uranium in silicate rocks, lignites, 

carnotites, pitchblendes, and many other naturally 

occurring materials.

4. Phosphoric acid may be extracted directly 

after the addition of aluminum nitrate.

5. For the preparation of "pure" aluminum 

nitrate, the aluminum nitrate is dissolved in (15 + 85) 

HNC-3 in the proportion of 9-1/2 g A^NC^s' 9HgO to 

5 ml of HNO3 and extracted with ether instead of ethyl 

acetate. After the separation of the two layers the 

aqueous solution is evaporated until about one-third 

of its volume is removed and then is cooled to allow 

the aluminum nitrate to crystallize. The crystals are 

filtered off on a Buchner funnel and dried in air and 

stored.

Example 2: Determination

of 0.00001 percent uranium in feldspar

Application. --This procedure (Robert Meyrowitz, 

personal communication) is designed for use when the 

amount of sample available is small and the uranium 

content low.

Precautions. --For the determination of such 

small amounts of uranium scrupulous cleanliness must 

be observed. All reagents should be sufficiently free 

from uranium so that no significant blank is obtained. 

The nitric acid and hydrofluoric acid should be purified 

by distillation if necessary. The hydrofluoric acid 

can be distilled with a platinum still but it is better to 

test the HF from various suppliers and select one with 

a low uranium content. The aluminum nitrate used 

as the salting agent invariably requires purification 

which should be repeated if necessary until a reasonably low blank for uranium is obtained. A blank should 

be run on all the reagents as used in the procedure 

and it should be deducted from the results obtained on 

samples.

Procedure. --1. Weigh 0.0250 g of finely ground 

feldspar and transfer it to a small platinum dish. Burn 

off organic matter if present. Cool.

2. Add 2 to 4 drops of water, 2 ml HF, and 

0.5 ml of HNC»3. Digest the sample on the steam bath 

and evaporate the solution to dryness. Cool.

3. Add 2 ml of (1 + 1) HNOs and evaporate the 

solution tc dryness. Repeat. Cool.

4. Add 3 ml of A1(NO3 ) 3 -HNO3 solution by 

pipet. (See note 1, p. 7.) Warm gently to effect 

complete solution. Mix by swirling. The heating 

should be conducted in a manner that avoids any loss 

of solution through evaporation. Cool.

5. Pipet 2 ml of the solution to a 20-ml glassstoppered test tube.

6. Add 5 ml of ethyl acetate and shake for about 

30 sec. Allow the layers to separate for about 5 min.

7. Filter most of the ethyl acetate layer through 

a dry no. 42 Whatman 5.5-cm paper into a dry test 

tube (which holds the filter paper).

8. Transfer 3 ml of the filtered ethyl acetate 

to a standard platinum container. Place the dish on 

several layers of water-soaked absorbent paper which 

rests in a pan containing about 1/16 in. of water.

9. Immediately ignite the ethyl acetate by means 

of a lighted splinter and allow the ethyl acetate to 

burn completely.

10. Ignite gently to destroy organic matter.

11. Add 2 g of the specially prepared fused flux 

and prepare the phosphor as previously described.

12. Measure the relative fluorescence with the 

transmission instrument at highest sensitivity.
Notes: 1. Preparation o 

reagent

a) Dissolve 190 g A 1(NO3)3' 9H2O in 100 ml 

of (15 + 85) HNOs(use redistilled nitric 

acid). Cool.

b) Add an equal volume (about 200 ml) of ether 

and extract in a separatory funnel for about 

one minute. Allow the layers to separate.

c) Filter the aqueous layer through a fast filter

paper into a pyrex bottle.

If, after this preparation, the A1(NC>3)3 still has a 

significant blank, it should be crystallized from this 

solution and the extraction-purification procedure 

repeated.

Example 3: Determination of 

10"' percent uranium in fresh, 

saline, and sea water

Principles. --Preliminary concentration of the 

uranium is made by precipitating uranyl phosphate 

using aluminum phosphate as the carrier (Pietsch 

and Grimaldiji

Procedure. I. Transfer a 500-ml aliquot of 

water to an 800-ml beaker.

2. Add 3 ml of HNOs, 20 mg Al2Os (using a 

solution of aluminum nitrate), and 5 ml of (NH4)2HFC4 

solution (1 cc " 12 mg (NH^HPC^). Heat to boiling 

-to remove CC>2.

3. Add ammonium hydroxide until methyl red 

indicator is just yellow.

4. Digest the precipitate on the steam bath for 

about 10 min. Stir in paper pulp.

5. Filter the solution on a fast paper and wash 

the precipitate with 1 percent NH^NCs solution.

6. Transfer the precipitate and paper to a 

25-ml clean porcelain crucible and ignite at a low 

temperature until the paper is completely ashed .

7. Add 5 ml of (15 + 85) HNOs and warm gently 

to dissolve the salts (avoid any evaporation of solution).

8. Add 9-1/2 g A 1^03)3' 9H2O and warm to 

dissolve the salt.

9. Pour the solution into a 30-ml glassstoppered graduated test tube draining as completely 

as possible. Do not wash the crucible.

10. Add 10 ml of ethyl acetate by pipet and shake 

the mixture for about 30 sec. Allow the layers to 

separate for a few minutes.

11. Filter about 8 ml of the ethyl acetate through 

a dry paper into a dry test tube.

12. Transfer a 2-ml aliquot of the filtered ethyl 

acetate into a standard platinum container and burn it 

off as previously described under the extractionfluorimetric method.

13. Add 2 g of flux and prepare the fluorescent 

melt as before.

14. Measure the relative fluorescence of the 

melt with either the reflection or transmission instrument.

Notes: 1. In sampling waters in the field, it is 

good practice to add acid (about 8 ml HNOs per gallon 

of water) immediately after collection. Should the 

water sample contain sediment, it is necessary to 

filter the water when collected before the addition of 

the acid. Unacidified water samples tend to decrease 

in uranium concentration during storage; some of the

uranium is precipitated and some adsorbed on the 

glass (Koczy, 1950).

2. Alternately, fresh water and waters containing relatively small amounts of dissolved salts can 

be evaporated and the extraction procedure applied 

without preliminary concentration of the uranium with 

aluminum phosphate.

Carbonate-fluorimetric method 

Range: 0.001 percent U and more 

Application

The method is generally applicable except for 

samples unusually high in thorium and cerium such 

as high-grade ores of these elements. With suitable 

modifications, however, the procedure may be used 

even for the determination of uranium in monazite, 

as given in a later section.

Preparation of the 

solution for analysis

Silicate, carbonate, and phosphate rocks. --Attack 

by HF-^SC^i mixture. Nitric acid is avoided because 

the sodium nitrate formed by the alkali carbonate 

attacks platinum during the preparation of the phosphor. 

This leads to low results due to platinum quenching.

Refractory materials. --Fusion with a mixture 

of K2S2Oy-NaF or NaF alone followed by removal of 

fluoride with ^804.

Fluorimeters

The fluorescence may be measured by either the 

reflection or transmission fluorimeter.

Example 1: The fluorimetric determination 

of uranium in lignites after alkali carbonate 

separation (Guttag and Grimaldi,1951)

1. Weigh a 0.150-g sample (-80 mesh) into a 

70-ml platinum dish.

2. Ignite the sample gently to remove organic 

matter. Cool and moisten the sample with water.

3. Add 0.5 ml ^804 (by pipet) and cautiously 

add 5-10 ml of HF. Digest the sample on the steam 

bath and then evaporate the solution to remove water.

4. Bring the sample to fumes of sulfuric acid 

and fume for several minutes. Cool.

5. Add 25 ml of water cautiously, digest the 

sample on the steam bath, and stir to dissolve the 

salts. Cool to room temperature.

6. Transfer the contents of the dish to a 50-ml 

glass-stoppered graduated cylinder. Dilute to 50 ml 

with water. Mix.

7. If suspended insoluble sulfates are present, 

mix the solution thoroughly. Immediately draw off 

a 5-ml aliquot and transfer the solution to a 25-ml 

glass-stoppered test tube.

8. Add 5 ml of mixed carbonate solution 

(10 g Na2CO3 + 10 g K2CO3 per 100 ml of water) 

and mix.

9. Place the stoppered tube in a beaker of hot 

water and let stand for 10 min at about 90 C. If 

a blue solution persists (indicating copper), cool 

slightly and add 0.05 ml of hydroxylamine hydrochlo T 

ride (made by dissolving 20 g of NH2OH' HC1 in
100-ml H2O). Continue the heating at about 90 C for 

an additional 20 min for all samples whether or not 

hydroxylamine has been added.

10. Remove the tube from the bath and allow 

the solution to cool for 1 hr at room temperature.

11. Filter part of the solution through a dry 

filter paper (Whatman no. 42) into a dry test tube. 

The filter paper is conveniently held in place by the 

test tube.

12. Transfer an 0.80-ml aliquot of the solution 

to a standard platinum container and evaporate the 

solution on the steam bath. Ignite gently.

13. Add 2 g of flux and prepare the phosphor as 

described in the Direct method.

14. The relative fluorescence of the melt is then 

read in the reflection or transmission fluorimeter.

Notes: 1. The amount of sulfuric acid added in 

preparing the solution must be controlled. If more 

than the prescribed amount is used, the additional 

alkali sulfates formed in the carbonate step may alter 

the composition of the flux sufficiently to change its 

sensitivity. Nitric acid solutions are to be avoided, 

but hydrochloric acid solutions are permissible.

2. The same general procedure is used for determining uranium in shales and other silicate rocks, 

carnotite and other naturally occurring materials.

Example 2: Determination of uranium

in monazite after alkali carbonate separation

Range. --0.01 percent and more.

Application. --The method is especially useful 

for refractory materials. For samples containing 

much smaller amounts of cerium and thorium than 

occur in monazite, the range may be extended downward by use of larger samples.

Principles. --The procedure for monazite differs 

only on the method of preparing the solution and in 

the final size of sample taken. Almost all of the ' 

cerium is removed by alkali carbonate. What remains 

after the separation would normally quench the uranium 

fluorescence in a 1.2-mg sample of monazite. The 

uranium content of monazite is usually greater than 

0.1 percent. This fact enables us to use the dilution 

method after the carbonate separation, and for a 

0. 12-mg aliquot quenching by cerium is eliminated.

Procedure._--!. Weigh 0.0800 g of finely ground 

monazite into a platinum crucible.

2. Add 0.6 g of flux (2 parts by weightNaF and 

3 parts by weight K^SgOy).

3. Fuse the sample over a low burner until a 

clear melt is obtained (about 30 sec). Cool.

4. Add 0.4 ml of concentrated H2SO4- Heat gently 

until all thefluoride is removed and a clear pyrosulf ate 

melt is obtained. This fusion proceeds through several 

stages. In the first stage some frothing is apparent until 

the melt disintegrates. The melt is usually colored 

and muddy at this point. In the second stage the melt 

thickens and becomes lighter in color. In the final stage 

a clear pyrosulfate melt is obtained. The total time for 

the complete process is about 3-1/2 min. Cool.

5. Add 10 to 15 ml of water and 2 ml H2SO4 

by pipet. Digest the melt on the Steam bath. Stir 

occasionally until the melt is completely disintegrated.

6. Transfer the sample to a 100-ml glassstoppered graduated cylinder and make up to 100 ml

with water. Mix. Generally a complete solution is 

obtained within 5 min. Sometimes a cloud (presumably 

anhydrous rare-earth sulfates) persists after 5 min. 

This is not important as long as the sample has been 

completely decomposed.

7. Disperse the mixture by shaking. Immediately 

draw off a 5-ml aliquot and transfer to a glass-stoppered test tube.

8. Proceed according to steps 8 through 11 of 

the procedure for lignites.

9. Take a 0.30-ml aliquot at step 12 and proceed as directed for lignites steps 12 through 14.

Notes: 1. For refractory materials not broken 

up by K^^Oy-NaF flux, use pure NaF as the flux.

2. The range for monazite may be extended 

downward to 0.001 percent uranium by using the fused 

flux and the transmission instrument set for high 

sensitivity.

DETAILS OF FLUORIMETERS 

Reflection fluorimeter (Fletcher and May. 1950)

The reflection fluorimeter described in this 

report is a modification of the Oak Ridge Model R 

fluorimeter (Coleman, 1949). The new 

instrument was designed to better meet the needs of 

the Survey Laboratory with respect to sensitivity and 

stability. The model described in this report is an 

early one and can be built with relatively limited shop 

facilities. Organizations with a good shop can readily 

make appropriate modifications in the design to enable 

the construction of a more compact and rigid instrument.

The instrument is built on the base of the 

Model R fluorimeter and retains the sample slide, 

the Fhotovolt measuring unit, and the secondary 

filters of the Model R instrument. The substitution 

of the more intense General Electric E-H4 or C-H4 

lamp in the new instrument increases the sensitivity, yet 

allows the continued use of the Fhotovolt electronic 

photometer (Model 512). The lamp is supported on 

a stand and is ventilated by a ventilating fan (obtainable at photographic stores). After an initial warmup 

the operating temperature remains constant, and the 

lamp can be left on all day if desired. As the lamp 

is not mounted directly on the instrument, the distance 

between the lamp and the sample may be readily 

changed, thus providing for greater or less sensitivity.

The housing for the filters and shutter is made 

from 26-gauge sheet brass painted a flat black 

(figs.'5, 6, 7). A no. 6 Packard shutter, obtainable 

from photographic shops, with a 1-1/2-in diameter 

opening is attached directly above the secondary 

filters. The top plate of the shutter is replaced with 

a bakelite cover having a 1-1/4-in diameter hole in 

the center. One end of a brass collar is held in this 

hole by a friction fit, and the other end is threaded 

to screw directly into the search unit. All joints are> 

secure and light tight. The secondary filters are the 

yellow and green filters (Corning nos. 3486 and 9780, 

moulded thickness). The Corning filter no. 5874, 

3-1/4-in square, serves as the primary filter. A 

sheet-metal shield provided with air vents is placed 

around the instrument, and the enclosure is ventilated 

with the ventilating fan. The sample slide has two 

2-inch-square depressions cut in line with each other
AX I ki did. tubing- one end 

threaded to fit search unit

drill 4 holes (one each corner) 

to suit Packard shutter

SEARCH UNIT 

CONNECTOR

SHUTTER COVER 

PLATE

slot for extended arm 

to Packard shutter

drill 2 holes for placement 

of shutter trigger mechanism

provide I Vdia.hole- counter bore to provide 

friction fit for search unit connector

drill 4 holes (one each corner) 

to suit Packard shutter

PRIMA

SECONDARY FILTER 

FRAME

EXPANDED DETAILS 

OF THE

MODIFIED FLUORIMETER

(rear view)

Figure 5. --Expanded details of the modified fluorimeter.
A- Lamp

B- Primary filter

C- Primary filter frame

D- Housing

E- Housing

F- Secondary filter frame

G- Secondary filter

H- Shutter base frame

I- St'd. ife" Packard shutter

J - Shutter cover plate

K- Shutter trigger

L- Search unit connector

REAR VIEW ASSEMBLY 

OF THE

MODIFIED FLUORIMETER

Figure 6. --Rear view assembly of the modified fluorimeter.

10
COMPLETE ASSEMBLY 

OF THE

MODIFIED FLUORIMETER

(front view)

Figure 7. --Complete assembly of the modified fluorimeter.

11
so that either one may be placed in the path 

of the ultraviolet light beam. A standard 

fluorescent glass is mounted in one of the depressions; an adapter to accommodate the sample 

discs is mounted in the other depression. The 

standard glass provides a convenient reference 

point in terms of which both the relative fluorescence of standards and of samples are measured. The reading due to the fluorescence of 

the standard glass is adjusted to a fixed value 

near the upper part of the scale -- large adjustments are made by varying the height of the 

lamp, smaller adjustments are made with the 

sensitivity control of the photometer. The standard fluorescing glass which we use is the 

Corning filter no. 3384, standard polished thickness, melt 600. We have found that there is a 

pronounced difference in the fluorescence of one 

or the other side of these filters and there is 

an even greater difference in the intensity of 

fluorescence of filters from other melts. 

Figure 8 illustrates a typical curve relating the 

intensity of fluorescence of uranium ("Lo" scale 

reading on Fhotovolt electronic photometer 

Model 512, standard glass set for a deflection 

of 80) with the amount of uranium in a 2-g melt. 

Using the "Lo" scale of the photovolt photometer, 

the sensitivity of this instrument allows 10"8 g 

of uranium to be determined as a lower limit 

for a 2-g melt.

O.I 0.2 0-3 0.4 

Micrograms of uranium in a 2-g melt

Figure 8, A working curve for a "reflection"

fluorimeter.

Transmission fluorimeter

The word "fluorimeter", in quotation 

marks, as used in this section refers to that 

part of the complete fluorimeter which houses the 

filters, sample slide, and shutter.

The model V transmission fluorimeter 

(Fletcher and others, 1950) is machined from 

solid brass. The fluorimeter head includes the 

sample slide, shutter, and a holder for the

primary filters. The sample slide is provided 

with adapters so that several sizes of fluoride 

melts may be accommodated. The secondary 

filters are in the bottom plate which screws 

into the fluorimeter head. The bottom plates are 

of two types - A and B. Type A is used with 

an RCA-1F21 photomultiplier tube or with the 

Fhotovolt photometer. It is threaded to fit the 

Fhotovolt search unit. Housings for the 1F21 

photomultiplier tubes were built to have the same 

thread as the Fhotovolt search unit so that either 

phototube can be used with the type-A plate. 

The type-A plate is constructed so that phototube 

housings can be removed or installed while the 

fluorimeter is in position on the supporting 

stand. The type-B bottom plate is used with the 

RCA 5819 photomultiplier tube. The cinch no. 3M14 

socket with mounting ring 3R14 is used with 

this tube.

The filter holders are made for 2-inchsquare filters. An adapter ring for each filter 

holder permits the use of filters of different 

thicknesses.

The instrument is shown in detail in 

figures 9-15. In figure 9, one-half of drawing 

A is a section showing the fluorimeter assembly 

with type-A bottom plate and Fhotovolt search 

unit in place; figure 9, drawing B shows the 

arrangement with type-B bottom plate and RCA-5819 

photomultiplier tube. The stand, lamp support, 

and shield are the same for both arrangements. 

Figure 10 is a cut-away drawing showing 

additional details of the fluorimeter. The remaining figures are detailed shop drawings for the 

construction of parts shown in figures 9 and 10. 

All parts of the fluorimeter shown in figures 11 

and 12 must be machined to a class-4 fit or 

better; those shown in figure 13 need be only 

a class-3 fit.

A thin glass disc (not shown in figures) 

is required in the sample slide under the adapter 

ring. The purpose of this disc is to prevent 

flakes of the melt from falling into the fluorimeter. This glass must be nonfluorescent. 

Discs cut from photographic plates used in spectrum analysis are satisfactory.

The lamp shown in figure 9 is a General 

Electric EH-4 or Ch-4 lamp. This lamp requires 

a porcelain socket with an ad medium base and 

is cooled by ventilation with a "Bon-Air" darkroom ventilator. The lamp is operated with a 

Sola no. 30,852 constant-voltage transformer 

designed especially for H-4 lamps.

The primary filters are 2-inch-square 

Corning no. 5874 ultraviolet filters, standard 

polished thickness. Two of these filters are 

generally used. The secondary filter may be 

either a combination of Corning filters nos. 3486 

and 9780, standard moulded or polished thickness, 

or an interference filter peaked for maximum 

transmission at 5550 A.

Various combinations of phototubes and 

current amplifying and measuring devices which

12
Shield supports

Adjustoble lamp support assembly

Support rods 3/4 inch stainless steel 29inchs high

Fluorimeter<'support

Filters 2" x 2" x 3/1(5 to 1/2"

Adapter ring

Glass sample plate

Sample slide

Shutter

Filters 2"x2"x 3/IO"to 1/2"

Filter ring

Amphenol connector

Support for tube socket

B

Figure 9, --Fluorimeter assembly (transmission). 

13
FELT PAD 

TO BE GLUED

FILTER

"FLUORIMETER" ASSEMBLY WITH BOTTOM FILTER PLATE TYPE "A" 

CUT AWAY SECTION EXPOSING CONSTRUCTION, SHUTTER OPEN

FLUORIMETER HEAD

15

14

13

12

II

10

9

8

7

6

5

4

3

2

1

SLIDE ADAPTER 

FLAT HEAD SC

FLAT HEAD SC

BOLT

HDLS. SET SCR

BUTTON HD. S

BUTTON HD. S

TOP PLATE

BLACK OUT PL

FILTER RING

FILTER PLATE

FILTER CLIP

FILTER CLIP

SPANNER NUT

PLATE FLANGE

BOTTOM FILTE

SHUTTER

SHUTTER SLID

SLIDE GUIDE L

SLIDE GUIDE R

SAMPLE SLIDE

FLUORIMETER 

ALL FITTINGS 

CROSS-SECTION OF BOTTOM FILTER PLATE "B" 

AT ASSEMBLY IN TUBE

Figure 10. --Fluor imeter -- cut-away and cross-section.
TAP *4-40 THD. 4 HOLES 

LOCATE FROM TOP

DRILL S CO. SINK FOR

No. 8-32 FLAT HEAD SCR.

4 HOLES SLIDE GU

I R. HAND AS SHOWN AN

SPOT FROM BLACK 

OUT PLATE "

(T)"FLUORIMETER' HOUSING I REQ'D

2) SAMPLE SLIDE I REQ

FILTER CLIP 8 SEQ'D 

10) (\\

5/32 E

5) SHUTTER PLATE I REQ'D

DRILL a C-SINK FOR 

No.6-32 FLAT HD. SCR. 

4 HOLES

Figure 11. Details of parts shown in figure 10.
5/6 DEEP 4 HOLES

BOTTOM FILTER PLATE TYPE A 

I REQ'O

BOTTOM FILTER PLATE TYPE B 

I REQ'O

No 32 DRILL (.IIS'D

I/B DRILL 3/B DEEP

8 4-40 TAP FOR

OLS. SET SCR

SPANNER NUT I REQ'O 

(9)

DET REQ'O

I

I

1

1

DIM. A

1.050

.800

.6ffD

.39JD

DIM. B

I.4CTD

I.I5D

.9SD

.74SD

ADAPTER RING 4 REQ'O

"BLACK 

E

Figure 12. --Details of parts shown in figure 10.
10-32 N, F thumb screw

(A)Shield supports 

2 required

drill 7 holes (vents) 

JX "die.

-32 MF.

F/uorimefer"

drill 

10-

CD) "F

Top for shield

Figure 13. --Details of parts shown in figure 9.
HOUSING MATERIAL Ufi ALUM.

FELT -LINE INSIDE AROUND SLOT

LATCH ASS'Y FOR 

DOORS MAT- BRASS

I '/2 SPH RAD 

KNURL

LARGE DOOR SHAPE TO FIT 

HOUSING AT ASS'Y. MAT- !/| 6" ALUM

No. II DRILL (.191 DIA ) FOR LATCH

SMALL DOOR SHAPE TO FIT CONE 

TOP AT ASS'Y. MAT.-'/ig ALUM.

2 HOLES 

TO SUIT HINGE 

SPOT AT ASS'

1

Figure 14. --Details of construction of shield.

have been used with this fluorimeter have been 

described elsewhere (Fletcher, May, and Slavin, 

1949; May and Fletcher,, 1950).

Figure 16 illustrates a typical working 

curve relating the uranium content of a 2-g disc 

to its- relative fluorescence. . Fluorescence measurements were made with the Fhotovolt photometer

Model 512 using the "C" search unit and most 

sensitive scale. It is apparent that as little 

as 3 x 10 "10 g of uranium may be measured.

Unlike the reflection instrument where all 

fluorescence measurements are referred to a 

standard fluorescing glass, the transmission 

fluorimeter measurements are referred to a

18
CORRECTION SHEET 

U. S. Geological Survey Circular 199

Please substitute attached sheet for pages 

1? and 18 of this circular.

IO-32 fll F thumb screw

(A)Shield supports 

2 required

drill 7 holes (vents) 

a/. "dla.

-32 N.F.

Fluorimeter* £\ 4" radius

F

Top for shield

Figure 13. --Details of parts shown in figure 9.
HOUSING MATERIAL V!6 ALUM.

FELT-LINE INSIDE AROUND SLOT

LATCH ASS'Y FOR 

DOORS MAT- BRASS

LARGE DOOR SHAPE TO^FIT 

HOUSING AT ASS'Y. MAT- '/|6" ALUM

SMALL DOOR SHAPE TO FIT CONE 

TOP AT ASS'Y. MAT.-'/|6 ALUM

Figure 14. Details for construction of shield.

18
COUNTER BORE FOR 

AMPHENOL CONNECTOR 

NO. AN- JI02A-I4S-SS

DRILL & CO SINK FOR

SECTON A-A

PHOTOTUBE HOUSING I REQ'D 

I HOUSING CAP 

Material Aluminum 

Fittinqs to be light tight

TUBE PLUG FLANGE 

\ 

Figure Figure. 15. --Details of construction of phototube housing type B.
80

70

0.001 .002 .003 ,004 .005 .006 .007 .008 

Micrograms of uranium in a 2-g melt

Figure 16. A working curve for a transmission

fluorimeter.

"standard deflection" which is a reading obtained 

with no sample in position. The standard deflection 

results from filter leakage and fluorescence and has 

been found to be reproducible. This reading may be 

adjusted to a convenient figure by changing the position of the lamp or the sensitivity controls on the 

photometer.

LITERATURE CITED

Atomic Energy Commission, 1949, Assayer's Guide, 

New Brunswick Laboratory, AECD 2640.

Coleman, C. F., in Atomic Energy Commission, 

1949, Assayer's~Guide, C-4.381.4, March 11, 1946.

Fletcher, M. H., 1950, A study of the critical factors 

in the "direct" fluorimetric determination of 

uranium: U. S. Geol. Survey Trace Elements investigations Rept. 130. [ Unpublished. ]

Fletcher, M. H., and May, Irving, 1950, An improved 

fluorimeter for the determination of uranium in

fluoride melts: U. S. Geol. Survey Trace Elements 

Investigations Rept. 120. [In open file. ]

.Fletcher, M. H., May, Irving, and Anderson,J. W., 

1950, The design of the model V transmission 

fluorimeter: U. S. Geol. Survey Trace Elements 

Investigations Rept. 133. [In open file. ]

Fletcher, M. H., May, Irving, and Slavin, Morris, 

1949, A transmission fluorimeter for use in the 

fluorimetric method analysis for uranium. 

U. S. Geol. Survey Trace Elements Investigations 

Rept. 104. [ In open file. ]

Grimaldi, F. S., and Guttag, N. S., 1950, Short 

routine direct method for the fluorimetric determination of uranium in phosphate rock: U. S. Geol. 

Survey Trace Elements Investigations Rept. 134. 

[ Unpublished. ]

Grimaldi, F. S., and Levine, Harry, 1950, The rapid 

fluorimetric determination of uranium in low-grade 

ores, AECD 2824.

Guttag, N. S., and Grimaldi, F. S. , 1951,

Fluorimetric determination of uranium in shales, 

lignites, and monazites after alkali carbonate 

separation: U. S. Geol. Survey Trace Elements 

Investigations Rept. 153-A. [Unpublished.]

Jacobs, S., 1950, A study of the determination of 

uranium by measurement of fluorescence: 

CRL/AE54, Dept. of Scientific and Industrial 

Research, Teddington, England.

Koczy, Gerta, 1950, Weitere Uranbestimmungen an 

Meerwasser-proben: Akad. Wiss. Wien. Math. 

naturwiss. KL. Sitzungber, Abt. Ea, 158 Band, 

1-5 Heft, pp. 113-122.

May, Irving, and Fletcher, M. H., 1950, A batterypowered fluorimeter for the determination of 

uranium: U. S. Geol. Survey Trace Elements 

Investigations Rept-. 135. [Unpublished.]

Nichols, E. L., and Slattery, M. K., 1926, Uranium 

as an activator: Optical Soc. America Jour., 

vol. 12, p. 449.

Pietsch, Audrey, and Grimaldi, F. S., The fluorimetric 

determination of uranium in nonsaline and saline 

waters: U. S. Geol. Survey Trace Elements 

Investigations Rept. [ In preparation. ]

Price, G. R., Ferretti, F. J., and Schwartz, S., 

1945, The microfluorimetric determination of 

uranium, AECD 2282.

Rodden, C. J., 1950, Analytical chemistry of the 

Manhattan Project, National Nuclear Energy Series, 

New York, McGraw-Hill Book Co.

20

INT.-DUP. SEC., WASH., D.C.2«7«1