Model '54 Transmission and 

Reflection Fluorimeter for 

Determination of Uranium 

With Adaptation to 

Field Use

GEOLOGICAL SURVEY BULLETIN 1036-M

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

Model '54 Transmission and 

Reflection Fluorimeter for 

Determination of Uranium 

With Adaptation to 

Field Use

By ERNEST E. PARSHALL and LEWIS F. RADER, Jr.

CONTRIBUTIONS TO GEOCHEMISTR

GEOLOGICAL SURVEY BULLETIN 1 0 3 6-M

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

UNITED STATES GOVERNMENT PRINTING 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 

Washington 25, D. C. - Price 60 cents (paper cover)
CONTEXTS

	Page 

Abstract _____ _ _______________ ________________ 221

Introduction _ _ ____ ______________ _________________ 221

Acknowledgments __ ________ _ __________ ______ 222

Description of fluorimeter.. ____ ________ __ _______ ________ 222

Electrometer and phototube assembly _______ _ ___. _ _________ 224

Adaptation To field use ______________ _ _____ ____ ___ ___ _ __ 238

Discussion of black-light lamp____ _ ___ _ _____ _ _____________ 240

Operation of amplifier circuit____ _______ _ _ ___ __ __________ 241

Instructions for adjustment of instrument . _______ _ _ _ ------- 242

Calibration and adjustment of range. ____ __ _ _ __________ _ 243

Discussion._ _________ _ __________ ___ _ _ ______ ___ _ __ 246

List of parts for Model '54 fluorimeter. ______ _ _ __ _ ___ ________ 248

Literature cited__._ ____ ___ _ _ - ____ _________ __ __ _____ ___ 250

ILLUSTRATIONS

Paee 

PLATE 3. Separation drawings showing component parts of transmission

and reflection units _______ _ ________ __________ In pocket

FIGURE 31. Assembled fluorimeter, Model'54____ _ .______________-_-- 223

32. Phototube assembly and shutter arrangement-_----____ __ 225

33. Switch and shutter arrangement in search head-. ______ ____ 226

34. Location of wiring and parts in amplifier cabinet ______ _ ___ 229

35. Wiring diagram of Model'54 fluorimeter____ ___ _________ 230

36. Modification of wiring diagram for operation on dry-cell

battery. ___ __ ____________________________________ 231

37. Wiring diagram of battery test circuit ______ _______________ 232

38. Transmission assembly, RP-12 ultraviolet lamps ard housing,

light filters-, and mount for 7 1 2-volt C batteries. _________ 235

39. Reflection assembly, slide holding position for flux wafer, and

two masked glass standards-_._--___________-- _________ 236

40. I'ltraviolet lamp power source operated on house circuit______ 237

41. Wiring diagrams and parts_______ ________________ 238

42. Change of range and sensitivity of low scale available within 

range of sensitivity control without other changes in instrument ______ _____________________ _ ____________________ 245

43. Effect of temperature change (28° to 40° C) on stability of

phototube and reproducibility of instrument readings___ __ 248

CONTRIBUTIONS TO GEOCHEMISTRY

MODEL '54 TRANSMISSION AND REFLECTION

FLUORIMETER FOR THE DETERMINATION

OF URANIUM, WITH ADAPTATION

TO FIELD USE

ERNEST E. PAKSHALL AND LEWIS F. TRADER, JR.

ABSTRACT

The model 'H4 fiuorimeter for the determination of uranium by the Muorimetric method has been designed, built, and used in the 1 . S. Geological Survey 

since 19uO, and is one of several such instruments developed by the Geological 

Survey. An adaptation for field use is included in the present description of the 

instrument. The circuit Is a modification of that used in the Beckmau DU 

spectrophotometer and incorporates an electrometer, amplifier, and blue-sensitive phototube as used in the DTT instrument because of the extraordinary 

sensitivity obtained for a phototube of this type. The low-voltage circuit used 

in the Model '54 fiuorimeter results in an unusually broad working range of 

high sensitivity and stability for the instrument. Changes in temperature have 

little or no effect on the accuracy uf readings made under conditions expected in 

field work. A detailed description of the instrument and of its use in fields and 

laboratory is accompanied by photographs, working drawings, and instructions 

that would make possible its construction in the average machine shop.

INTRODUCTION

Fhiorimetric methods for the determination of uranium were developed before commercial fhtorirneters were available. Investigators 

in various laboratories, therefore, generally built their own instruments. Pioneering in the design of fhiorimeters were Price and coworkers in 1045 and 1048 (Price, Ferretti, and Schwartz, 1053); 

Fischer and Pickle (1040); Center (1040): Davey and Florida 

(1940); Jacobs (1050); Tvaufman and others (1050); Zimmerman 

(1950) ; Teaman (1051) ; Ivelley and coworkers ( 1054) ; and Galvanek 

andMorrison (1054).

TJ. S. Geological Survey chemists have developed numerous Auorimetric instruments, several of which have already been described in 

publications. Fletcher and May in 1950 and 1054 reported a modification of the Oak Ridge Model R fluorimeter which had been in use 

since 104S. The first transmission instrument was reported in 1949 

and 1054 by Fletcher, May, and Slavin: the Model V transmission

221
222 CONTRIBUTIONS TO GEOCHEMISTRY

fluorimeter in 1950 and 1954 by Fletcher, May, and Andersen. A portable battery-powered field instrument was described in 1950 by May 

and Fletcher. Several features of the Model V and the field fluorimeters were incorporated into a compact laboratory instrument (the 

Model VI) by Kinser in 1954.

Reports on this early work, as now available to the public, are listed 

in the bibliography.

This paper describes another fluorimeter developed in the U. S. 

Geological Survey. This instrument, the Model "54, has been in use 

in essentially its present form since 1950. During this time it has 

been used daily for the determination of uranium in a large variety 

of materials totaling about 1,000 determinations per month so that 

the instrument has been thoroughly tested.

Requests from chemists who have received training in the fluorimetric method under the Atomic Energy Commission program and 

from private companies engaged in reconnaissance for uranium, and 

related mining activities, show that this instrument is particularly 

suited to their needs. This report, containing instructions, wiring diagrams, and descriptions of the Model '54 fluorimeter, has been prepared to make such information available to all those interested.

This report concerns work done by the U. S. Geological Survey on 

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

Commission.

ACKNOWLEDGMENTS

The advice and assistance of all who made possible the development, 

construction, testing, and description of this fluorimeter are gratefully acknowledged. G. J. Petretic, formerly of the Geological Survey, was largely responsible for the early development work. C. G. 

Bay and others of the Geological Survey aided in the design and construction of the instrument in the shops.

DESCRIPTION OF FLUORIMETER

This fluorimeter uses a circuit modified from that of the Beckman 

DU spectrophotometer: it also uses the three electronic tubes 

similar to those of the Beckman instrument. The phototube has extraordinary sensitivity for one of this type and requires no cooling 

arrangement for stable operation that has been found desirable for 

some types of photomultiplier tubes (Morton, 1955). The blacklight lamp is a 3-watt F 3 RP 12/GL type that operates satisfactorily 

without cooling. The amplifier unit is so constructed that either a 

transmission-type search head or a reflection type unit may be used for 

measurement of fluorescence independently. An adaptation of the 

instrument for field use with dry-cell batteries also is described. 

Either tho standard laboratory instrument or the field adaptation is
MODEL 'o4 TRANSMISSION AND REFLECTION FLUORIMETER 223
224 CONTRIBUTIONS TO GEOCHEMISTRY

designed to read a broad range of uranium concentrations in carbonate 

fluoride flux pads without exceeding the point at which the phototube fails to respond linearly to additional small increments of concentration or at which the phototube fails to recover rapidly from 

exposure to intense light. Thus it is possible to work in the range of 

from '2 x 10~9 to 3 x 10~5 grams of uranium in a 2 gram flux wafer, and. 

the use of extremely small samples, large dilutions, or tiny aliquots 

is generally not necessary.

The assembled instrument as used in the laboratory is shown in 

figure 31. In the foreground are the amplifier and control cabinet, reflection-type and transmission-type search units, respectively, from 

left to right. In the background are a commercial power supply designed to power a model DU spectrophotometer, a constant voltage 

transformer connected ahead of the small power supply in the right 

background. This power supply is for the two black-light lamps, 

one on each type fluorimeter search head.

The amplifier and control cabinet is made of ^-inch sheet aluminum 

cut and assembled to form a box 10 X11V, X iS% inches, sloping to 5% 

inches in front.

The amplifier unit may be operated with either a commercial power 

source, a 6-volt storage battery, or with dry cells as described later 

for field use. However, this unit also requires six radio C batteries in 

addition to the power source just mentioned.

ELECTBOMETER AND PHOTOTUBE ASSEMBLY

Different views of the phototube assembly and shutter arrangement 

of the search heads are shown in figures 32 and 33. The housing is 

made from sheet aluminum. Two sides are y± inch thick and two are y8 

inch thick so that the edges of the thick stock may be milled to lighttight fit. The two ends also are thick stock milled for the same reason. 

An aperture bored to a diameter of 1.276 inches is cut in one of the 

thin sides of the housing, 2*4 inches from center to one end of plate, 

threaded for attachment to the light-filter holder and lamp assembly 

(36 threads per inch). The overall dimensions of the assembled housing are 1014 x 2% x 2% inches.

All wiring in the phototube housing must be with waxed, cottonbraided, insulated wire because static electricity caused by moving 

the shutter slide is sufficient to cause serious interference with operation of the instrument if wire covered with synthetic insulation is 

used.

Identification and location of items in the phototube housing, figures 

32 and 33 are: Resistors, El, R2, R3, R4, and R5, with resistances of 

39 ohms, 47 ohms, 1 megohm, 150,000 ohms and 2,000 megohms, respectively; (I) are porcelain insulator mounts, (A) is the electrometer
MODEL '54 TRANSMISSION AND REFLECTION FLUORIMETER 225

427:!T4 ~:>7 -2
226 CONTRIBUTIONS TO GEOCHEMISTRY

FIGURE 33. Switch and shutter arrangement in search head.
MODEL \5 1 TRANSMISSION AND REFLECTION FLUORIMETER 227

amplifier tube (V2), type 32 for low grid current applications (Sylvania no. 1229, specially selected, Becknmn no. 2532, (B) is a darkcurrent switch (S4) operated by the shutter slide (C).

This dark-current switch is made from one set of contacts from a 

12-ampere. type 200-4 (riiardian relay contact assembly. Remove, 

one set of contacts from the assembly intact. Also remove the center 

blade, turn it over so that all connecting lugs are on the same side, and 

flatten the Mute in the end of the blade for attachment of a plexiglass 

block or shoe that will operate the switch, when finally assembled, 

whenever the shutter slide is moved. This block is made from % inch 

thick material cut to clear the end of the lower blade of the switch and 

carefully drilled and fitted before fastening to the end of the center 

blade with two round-head number 2-56 thread machine screws, iiend 

the upper and lower wire lugs away from the center one for more wire 

clearance. Mount the contact assembly on a piece of plexiglass ^ x 1 x 

i^ inch as shown (fig. 83). Either drill to bolt through the plexiglass 

or drill and tap for the number o-40 thread screws that come with this 

part, locate the blades of the assembly on the block with the stack 

spacer insulating washers Hush with the inside edge of the ^-inch 

dimension of the block in order to gain about i^-inch clearance from 

the side of the case. Also locate the assembly on the block near the 

right end as shown on figure 33. The block and switch assembly is 

then fastened to the side of the case with two number H-3% thread 

oval-head machine screws ^ inch long. Drill and tap the block for 

these screws, locating one midway between the two assembly screws 

and the other spaced ^2 iw'h toward the contact end of the block.

The switch must be positioned so that the shutter has just cleared 

the light opening before the switch operates. The vertical position 

is such that the shutter slide raises the center blade to clear the lower 

contact and to make contact with the upper blade. When the shutter 

plate closes (he. light opening, the center blade of the switch, which 

is connected through resistors R4 and Bn (fig. 3^) to the grid of the 

electrometer lube, is in contact with the lower blade thus grounding 

the grid circuit through the two resistors so that the dark current may 

be adjusted to zero on the meter. When the shutter plate is pushed 

in. light passes to the phototube as the center blade of the switch is 

raided to clear the lower or grounded blade, and the grid circuit is 

transferred to the upper blade which is connected to the slide-wire 

circuit through the range switch. This switch thus prevents operation 

of the inst rument when the opening to the phototube is not completely 

cleared because no readings can he obtained on the slide-wire dial, and 

the operator is warned to adjust the position of the shutter plate. Contact, tension adjustment of the swich is made by bending. With the 

light shutter open and switch in raised position, clearance of 0.02o
228 CONTRIBUTIONS TO GEOCHEMISTRY

inch should be allowed between contacts. The contacts must be adjusted so that they just make before break in order to avoid severe 

shock to meter needle when in use.

The shutter plate (C figs. 82 and 33) is aluminum, 23^ x 3% x % 

inches, cut so that the width is a free fit between the side of the 

housing. A brass operating rod for the shutter slide is % x 3% inches 

threaded at both ends for attachement to plate and pull knob. Attachment to the shutter plate is made off center so that interference 

with the opening to the phototube is avoided. The rod length is 

adjusted to allow about ^4-inch clearance of the opening in the search 

unit housing when the shutter slide is fully open. The phototube 

(Beckman 2342) (E) is mounted in plexiglass saddles by means of 

brass strips (F). bent to the desired radius so that thin cork strips may 

be placed between the saddles, strips, and the tube at both mounts. 

The saddles holding the phototube are mounted to an aluminum plate, 

2% x 4%6 inches, with a i^-inch-cliameter hole bored to line up with 

the threaded opening in the housing. This plate is fitted into %-inchdeep slots in both sides of the housing. A clearance of %-inch is attained between shutter plate and the bottom of the phototube. One 

hole is drilled through each side plate of the housing into each slot 

and tapped for a number 4-40 short Alien setscrew. These screws 

hold the tube mounting plate in place and allow for adjustment and 

alinement of the 114-inch hole, in this plate with that in the tube 

housing. The plexiglass is drilled and tapped for all screws. Sufficient 

space between the saddles must be left to allow for minor adjustment 

of the phototube window to the opening in the housing. The black 

cross, (IT), on end of housing is adhesive rubber insulating tape used 

to prevent a short circuit.

The electrometer amplifier tube (A, fig. 32) is held in a socket 

mounted 011 an aluminum plate, % x 2% inches square, recessed into 

slots in the sides of the housing but loose enough to allow removal 

or repositioning of plate and tube. The tube is mounted with the 

plane of the filament in a vertical position. Otherwise the filament 

may sag and cause failure of the tube. When the search head is 

turned on its side to be used in a different position than the usual one, 

the tube mount may be rotated 90 degrees in the housing and the 

plane of the filament kept vertical. Slots to position the mounting 

plate are l1"^ inches from center to end of housing plate.

Figure 34 shows the wiring underneath the amplifier cabinet cover 

and arrangement of parts. The resistors and other parts are further 

identified in the appendix and text. The circuit wiring diagram is 

shown in figure 35. At the top left of figure 34 is on-off toggle switch 

(53). This switch proved unsatisfactory because of variable contact resistance and has been replaced with 90° indexing, four-pole
MODEL '51 TRANSMISSION AND REFLECTION FLFOR1METEE 229

Fu;ruK -'!4. Location of wiring and parts in amplifier cabinet.
230 CONTRIBUTIONS TO GEOCHEMISTRY

-TV

(ELECTROMETER B PHOTO TUBE HEAD ~ |

Bl B2 f I B 1 B3 B5

FIGURE 35. Wiring diagram of Model '54 fluorimeter.

rotary ceramic switch with two poles wired in parallel to minimize 

contact resistance. At top center is slide wire (R16), and at top 

right is dark-current helipot (E15). Ceramic switches: left center 

is selector "reflection-transmission" (S2-), right center is range switch 

(Si). At lower left is battery-test voltmeter, 0-15 volt direct current, lower center is helipot (KIT) referred to as sensitivity control, 

lower right is meter with zero-center scale (Ml). Parts visible in the 

cabinet are: Left rear, LOO-megohm resistor (lilft) mounted on standoff insulators. The resistor shown is an I li( 1 type MVP number 

5304. However, the small resistor (El8) listed on page 249 is desirable. The tube is (V3) Beckman amplifier, number 2531. The 

two receptacles held in place with hexagonal nuts are KEC 1 and 3, 

figure 35. The two small receptacles are P4, figure 36, at the left, and 

one similar to P4 except that it is a four-wire type to prevent improper connections and replaces the cable connector, figure 36, for 

6-volt storage battery connection. Four of the O batteries are shown. 

These batteries are held in the case by a bakelite box 4% x 5%6 x 2 

inches, ID, cut from ^-iiich material. This box is fastened to the floor 

of the cabinet with two flathead 6-32 machine screws cut to exact length 

so that they do not protrude. The O batteries are positioned with number 1 nearest the tube and number 6 nearest the front of cabinet when 

connected according to diagram, figure 37. On the right side of the
MODEL '54 TRANSMISSION AND REFLECTION FLUORIMETER 231

PRESENT 3-CONDUCTOR #16 RUBBER 

COVERED CABLE NOW ON INSTRUMENT

TO NEG NO 2 BATTERY

CIRCUIT BELOW THIS LINE IS SAME 

AS SHOWN IN FI&35EXCEPT THAT 

CONNECTION FROM THIS TERMINAL 

IS CHANGED FROM COMMON GROUND 

THRU NEW SWITCH AS SHOWN HERE

FIGURE 3d Modification of wirin peration on dry cell battery.

cabinet (tig. 34) are switches So, S6, S7, and S8 (fig. 37) and S9, 

KID, R20, R21 and E22 (fig. 36). Shafts of all switches except S9 

are cut short and slotted for screwdriver adjustment. SO has a knob 

attached.

The C batteries are held together in the bakelite box by a sheet of 

plexiglass that hooks under a spring arrangement not shown. This 

sheet is 5^4 x 4% x l\$ inches. Drill 6 rows of six holes each in the 

plexiglass (fig. 3S). Locate the first row of holes % inch from the edge 

that will be positioned in front of cabinet. Space the other rows 1 

inch apart. Across the other dimension start the first row i/> inch 

from left side and space 34 inch apart. All holes are 1 %4 -mch diameter except the last row at the right, figures 34 and 38, and these are 

drilled to clear a number 6 machine screw. Terminal nuts are required on all posts of batteries 1. 2, and 3 but only on the end terminals 

of batteries 4, 5, and (5. Therefore prepare connections to these terminals by inserting a number 0 brass grominet and plain washer, with 

the washer down, and crimp in place. Crimp only enough to hold 

and prevent rotation. Solder connecting wires to the edge of the flange 

so that terminal nuts are cleared. The 0-volt terminal of batteries 

4, 5, and 0 is not connected but needs to be fastened for support when 

batteries are handled as a unit. Brass machine screws and thumb nuts 

(0-32 x i/o) are used in the small holes along the right side of the plexiglass as terminals to connect the TVs-volt pigtail leads of the C batteries. The wires from these terminals to the amplifier are soldered 

to lugs that are held in place by hexagonal nuts.

The, slide-wire dial (fig. 34) should be purchased complete with 

knob, shaft and stationary contact. (See list. p. 249.) The slide wire 

is mounted on the \\-inch-thick panel through a brass bushing. This 

bushing is made from ^1(rinch brass stock, cut to 0.760+ inch long, 

drilled for a riinnina'-fit of the knob shaft. One end is turned to O.r>00
232 CONTRIBUTIONS TO GEOCHEMISTRY
MODEL '54 TRANSMISSION AND REFLECTION FLUORIMETER 233

inch in diameter for a length of ll/^2 inch and threaded at 32 threads 

per inch. The other end also is machined down just to clear the inside 

of the knob. As this diameter is slightly more than i/o inch, a shoulder 

is thus obtained to stop the bushing when screwed into the threaded 

hole in the panel. When completed the bushing will be slightly longer 

than required, but it is carefully shortened to match the length of shaft 

in knob. The knob and shaft must be free-turning when the slide-wire 

hub is tightened against the shoulder at the end of the thread on the 

knob shaft. The flat eccentric headbolt and locknut on the slide wire 

must also have proper clearance on the under side of the panel. This 

spacing is also controlled by the length of the panel bushing. A 

fillister-head screw (no. 4 10) is screwed into the underside of panel 

to strike the eccentric stop on the slide-wire dial. This screw determines the zero position of the transmission scale of the slide wire and 

must be located so that the zero is lined up with the index line of 

the window.

The stationary contact is so mounted that when the zero scale setting 

is correct, the contact is just at the "O" end of the resistance wire. The 

leads to the terminals on the slide wire must be flexible, coil and uncoil 

as dial is rotated, and long enough to prevent binding. A support for 

these leads is provided by a circular piece of ^-inch plexiglass slightly 

smaller than the slide-wire drum. This support is separated from 

the drum with spacer washers and fastened to the dial-knob shaft with 

a standard 5/16 -inch fine-thread, hexagonal nut. Shielded phonograph 

pick-up arm cable IT1/) inches long is satisfactory for leads. The 

shield is connected to the "O" end of the resistance wire, the other end 

of wire to the two-lug terminal strip.

The resistors shown underneath the cover of the amplifier unit, figure 

34, are listed and identified on page 249 and also designated by number, 

figure 35. This arrangement required multiple resistors and parallel 

connections that may be replaced or simplified as follows: Replace 

R6a and b with a single 25- or 27-ohm 1-watt resistor; R7a and b 

and R8a and b may be combined in one lOU-ohm 1-watt resistor; likewise combine ROa and b and RIO in a single 10-ohm 1-watt resistor; 

replace the combination Rlla and b, R12, and R13a and b with one 

1000-ohm 1-watt resistor; also replace R14a and b with a single 150- or 

180-ohm 1-watt resistor. Calibration of the 0.1 to 1.0 range may be 

accomplished by changing either the 10- or the 100-ohm resistor or 

possibly both. This should cause either a greater or smaller change 

in the ratio of 0.1 to 1.0 and indicate whether more or less resistance 

is required for the correction. Usually an assortment of 10- and 100- 

ohm resistors varying within the 10 percent tolerance of standard resistors will enable one to find a particular resistor that will produce 

the correct, and desired value, provided the resistance of each is
234 CONTRIBUTIONS TO GEOCHEMISTRY

measured to select one either higher or lower in resistance, as indicated 

by the above test, to make the ratio correct.

The assembled cartridge for holding desk-cant is shown, on figure 

38, in position in the phototube housing and removed for a better view. 

This cartridge is made from a 4-inch piece of %-incli thin-wall conduit, 

drilled through on both sides, 90 degrees apart, to obtain 20 openings. 

Solder a brass disk 14 6 inch thick and % inch in diameter to one end 

of the conduit and a screw cap, which is removable, to the other so 

that the desk-cant may be changed quickly. A suitable cap may be 

made from an Amphenol series 91 plug by cutting the large-diameter 

shell away from the threaded end, leaving y16 inch of the large diameter on the threaded part for soldering to the conduit. The screw 

cap is made by soldering a disk in the beveled end of the small knurled 

nut from the plug. A series 91 Amphenol chassis receptacle is used 

to hold the cartridge in the phototube housing. Eemove the insert by 

turning off the crimped part of the shell but without removing the 

flange. The locating notch in the threaded shell is closed by soldering 

a piece of metal in it. This piece is then mounted in a hole bored in 

the corner of the front plate of housing. Locate this hole so that the 

flange of the receptacle just clears the inner side and top of the phototube housing. The round threaded nut holds this piece in the end 

plate. The large knurled ring from the plug clamps the cartridge in 

the receptacle. A liner of filter paper is cut to fit the assembled cartridge. This liner prevents dust from the desiccant from falling inside 

the phototube housing.

Figure 38 also shows the assembled housing used for transmission 

measurements but with the black-light lamp holder removed from the 

top and the search head removed from the bottom. Shop drawings 

for construction of this unit are given on plate 3A. The assembly is 

essentially a track, milled to hold a slide that carries three recessed 

square openings for the flux-pad holder and twro glass standards. 

Mounted above the slide is a 2-inch-square light filter (Corning 5840) 

and the black-light lamp with holder. Below the slide are mounted 

Corning light filters 3486 and 9780, also 2-inch polished squares, and a 

threaded fitting for attachment to the search head. A lighttight fit 

is obtained by machining the parts and lapping them together for 

close fit.

Figure 39 shows a side view of the assembly used for reflection 

measurements but with the slide, search head, and black-light lamp 

housing removed. Machine work and fitting of parts on the reflection 

assembly are more difficult than with the rest of the instrument. The 

unit must be lighttight and distances for light passage in the assembly should be as short as possible. A square opening is specified 

in this unit, rather than a round one, because tests showed that a
<Jt.,

38. - Transmission assembly, III' 12 ultraviolet lamps and housing, light filters, and mount for T'/i-volt ("' batteries. toCO 

Cri
236 CONTRIBUTIONS TO GEOCHEMISTRY

FIGURE 39. Reflection assembly, 

o

slide holding position for flux wafer, and two masked

glass standards.

more uniform light distribution and intensity could be achieved than 

was possible with a round hole. Construction of this unit may be 

simplified by having1 a casting made of the part above the button 

slide and machining to proper dimensions. Light filters of the same 

size and characteristics as those used in the transmission unit also are 

used in this unit except that primary filter 5860 gives better light control than 5H40 in this instance. The angle of reflection is 45° with 

the black-light lamp mounted on one side and the search head on top 

of the unit. Shop drawings of this unit are shown on plate SB.

Construction of the reflection unit (see B, separation drawing, 

pi. 3) may be simplified by eliminating parts marked Ha, Hb, He, and
MODEL 'o4 TRANSMISSION AND REFLECTION FLT7ORIMETER 237

Hcl, and substituting part F shown on plate 3-1. Ho\vever. the opening in part F (I 7 s-inch hole) need not be cut. but the overall width 

of part F must be the same as the base, part E, plate H/>. in order to obtain a tit. The track for part (r, plate 3/>, is milled so that the openings, (}-2 (part (I. pi. :>/>) will locate properly in the opening in the 

bottom of part K, plate 3/>. The assembly is mounted on base J, plate 

o/>. with spacers 1 inch long.

Figure 40 shows some construction detail for the power supply for 

the two black-light lamps when the instrument is operated on 110-volt 

alternating current. The housing for this unit is a commercially available miniature amplifier foundation cabinet. Th? wiring diagram is 

that shown in figure 41 for the low-cost power supply except that the 

transformer (T'2) feeds a duplicate rectifier and resistor circuit as 

shown for a second lam]) (h'g. 41). The two-lamp circuit (fig. 41) 

may be used if desired but will cost twice as much. The meter (M) 

and resistor ( R'2-\) shown face down in the housing are paired one 

.set for each lamp. Near the edge of th? chassis, left foreground, 

figure 40. is shown a 75-ohm adjustable resistor in series with a rio-ohm 

10-watt fixed resistor. This is duplicated on the other side of the transformer but not visible on the illustration. Adjustment of the h'laFiGi'HK 4u. Ultraviolet lamp power source operated on house circuit.
238 CONTRIBUTIONS TO GEOCHEMISTRY

ment voltage is made by removing cover of housing and changing 

position of slide contacts on the 75-ohm adjustable resistors. If the 

variable resistor (B23) called for (fig. 41) is used, probably it will 

be necessary to rearrange parts or use a larger box. Place all resistors 

and rectifiers above the chassis for better ventilation. Figure 41 

shows the switch (S12) fuse, and pilot light ahead of Tl in the circuit. 

Use the same arrangement in this unit. Receptacles are not visible 

in figure 40, but are shown in figure 31. If only one black-light lamp 

is to be operated, the small compact unit given in figure 41 is quite 

satisfactory and inexpensive.

TO OTHER

RP-12

LAMP

LOW-COST POWER SUPPLY 

FOR OPERATION OF ONE LAMP

SINGLE TRANSFORMER AND RECTIFIER-TYPE

POWER SUPPLY FOR OPERATION OF

TWO RP-12 LAMPS

OPERATION OF RP-12 LAMP

ON DRY-CELL POWER 

FIGURE 41. Wiring diagram and parts.

ADAPTATION TO FIELD USE

The basic instrument is the same for either laboratory or field use. 

However, field use requires a battery power source not only for the 

amplifier unit but also for the operation of the black-Light lamps. The 

following minor additions or changes are also required: (1) addition 

of a polarized receptacle or self-locating type plug in the amplifier 

case for connection with the battery power source. This additional 

connection is necessary even though the amplifier unit will operate on 

either a commercial power source or 011 a fi-volt automobile battery 

connected to the terminal plug shown in figure 34, because effective 

field use requires operation on TVs-volt dry-cell batteries, as will be
MODEL '54 TRANSMISSION AND REFLECTION FLUORIMETER 239

explained subsequently. Hot leads from batteries should not be connected to exposed pins because of possible short circuits with metal 

objects during transportation for field use. (2) An additional changeover switch on the amplifier case to make possible a quick change from 

power to battery operation. A suitable switch for this purpose is S9 

described in the parts list (p. 250). This additional switch must be 

placed in the circuit ahead of the one used to select the proper search 

head. (3) Addition of four resistors to the circuit as shown on figure 

36. These resistors are of 133. 30, 16, and 56 ohms, respectively, but 

the values are not critical and 130-, 27-, 15-. and 56-ohm resistors 

would be satisfactory. It is important that the additional resistor of 

tube V3 (fig. 36) be placed in the circuit between the ground and the 

filament in order to avoid a biasing effect on the tube due to a negative 

return.

Field operation of the amplifier circuit is accomplished by use 

either of five no. 6, 1%-volt dry-cell batteries, or of plug-in type 

Radio A heavy-duty batteries, connected in series to produce 7y2 volts. 

The intermediate tap is connected to the positive of the no. 2 cell to 

obtain 3 volts. The drain on each of the battery taps is as follows: 

negative, 145 milliamperes maximum: positive 3 volt, 40 milliampere 

minimum, 116 milliampere maximum: positive TVo volt, 34 milliampere constant. Thus it seems reasonable to expect intermittent 

operation of the instrument about 4 hours a day for 30 days as a minimum before it would be necessary to change batteries. Operation of 

the instrument on dry-cell batteries is advisable for at least two reasons, namely, this kind of battery is generally available in smalltown 

shops at reasonable cost and operation of the instrument is more stable 

and reliable with dry cells than with a 6-volt automobile battery because such a battery could not be recharged conveniently in the field. 

This would result in supply voltage drops and variations in voltage 

with changing conditions that could not be compensated for, particularly if a trickle-charger was not available. Dry-cell operation avoids 

such troubles during the life of the batteries because the slow drop in 

voltage with use is compensated for when dark-current and sensitivity 

adjustments are made during use of the instrument. The instrument 

shown and described in this paper has the field adaption features 

built in at time of construction.

The battery power supply for field use has been designed to power 

only one black-light lamp. However, the same lamp may be used on 

either the reflection or the transmission search unit interchangeably. 

The carrying case for this power supply has two compartments. Three 

no. 6 1 %-volt dry cells make up one unit to supply 414 volts to the 

filament. This unit is wired so that only the correct connection may 

be made because more than 4V2 volts would destroy the lamp filament.
240 CONTRIBUTIONS TO GEOCHEMISTRY

The other compartment is built to hold eleven no. 6, iy2 volt dry cells 

to supply 16% volts. This is about the minimum voltage required to 

start and operate the black-light lamp, but it has proved satisfactory. 

The wiring diagram for the battery power supply is shown in figure 

41. The switch (S-10, fig. -±1) is for starting the lamp, by raising the 

filament voltage momentarily to start conduction. This switch is 

closed for only a few seconds until the lamp starts. The battery (B 9, 

fig. 41) gives just enough voltage to start the lamp. The two sets of 

batteries are used in order to keep the drain in each set low and insure 

longer life. The filament current is about 170 milliamperes and the 

glow circuit requires about '200 milliamperes for satisfactory light 

output. Batteries arranged in two units as described should permit 

operation 4 hours a day for at least 30 days.

DISCUSSION OF BLACK-LIGHT LAMP

The small, 3-watt black-lamp used with this fluorimeter was first 

used in 1950 by May and Fletcher (1954) and also has been used by 

Kinser (1954). It is listed in the 1919 General Electric lamp catalog 

as F3 KP 12/360 BL. This lamp operates on very little power, generates but little heat, and produces an unusual amount of radiation in 

the wavelength region of 3650 A. The light output is extremely constant. Continuous operation 24 hours a day for a 3-month test period in the laboratory failed to show significant change. The operating characteristics of this lamp have not been available and so certain 

tests have been made as a guide to the use of this lamp. The filament 

operates on 4 volts but will withstand 41/2 volts momentarily to start. 

Because of variations in filament resistance in different lamps it is 

necessary to use a 40-olim potentiometer-type variable resistor (R23) 

or other adjustable type resistor in the circuit. When starting a lamp 

for the first time or if lamps are changed it will be necessary to connect a high resistance voltmeter (20,000 ohms/volt) across the common and filament terminals of the lamp socket. Use either the 6- or 

10-volt range and adjust resistor 23 for 4 volts filament circuit. This 

should start the lamp but after about 5 minutes the voltage must be 

readjusted to exactly 4 volts when the normal operating current of 

200 to 250 milliamperes in the glow circuit has been set. Both filament 

voltage and glow circuit current should be adjusted at the same time 

because a large change in either circuit will result in some change 

in the other. The glow circuit operates at 7 to 9 volts but requires 16 

volts minimum to start. The minimum operating current in this 

circuit is 200 milliamperes but 250 milliamperes is recommended for 

normal operation. The filament of the lamp causes ionization that in 

turn causes a current flow through the glow circuit and excitation of 

the fluorescent coating on the inside of the bulb. The current in the
MODEL : 54 TRAXSMISSIOX AXD REFLECTIOX FLUORIMETER 241

filament circuit is limited by a dropping resistor. At the instant of 

starting the glow circuit has infinite resistance resulting in the full 

voltage across the elements of the lamp. Thus the filament may be 

considered the cathode and the glow element the anode. When the 

filament heats up, conduction between the cathode and anode occurs 

which causes a lowering of the internal resistance and starts current 

flow. The current flow is controlled as conduction increases by suitable 

current-limiting resistors in order to prevent damage to the lamp. 

The intensity of the lamp for use on the fluorimeter is controlled by a 

40-ohm variable resistor placed in the glow circuit. A potentiometer 

for this purpose has the advantage of having no "oil" position. The 

KP-12, 3-1 amp has a double contact index base. One bayonet locking-pin is opposite the other, but staggered in distance from the base 

to prevent operation except in one position. Sockets for these lamps 

are available from (A)le-Hersee Co., Old Colony Ave., Boston, Mass., 

and the H. A. Donglass Manufacturing Co., Bronson, Midi. A usable 

socket for these lamps may be made from a double-contact bayonetsocket with threaded metal outer shell, by cutting out a new pin 

socket in one side to match the lamp-base pins.

OPERATION OF AMPLIFIER CIRCUIT

This instrument is a null-point type with provision for adjusting 

and balancing the entire circuit both dark-light and reading positions each time before measurements are made. It is substantially 

a direct-current voltage amplifier. Operation of the amplifier depends on a voltage drop across the 2<>00-megohm resistor in the grid 

circuit of the 2532 electrometer tube. A potential is maintained across 

the elements of the phototube at all times by C batteries 1 and 2. 

Phototube conduction is entirely dependent on the amount of light 

striking the tube. Therefore, in total darkness no current flow occurs in this circuit. Internal and external leakage, dust, moisture, 

fumes, and careless handling must be guarded against. All tubes are 

carefully selected, matched for characteristic performance, and aged at 

the factory so that replacements, when necessary, very nearly match 

the performance of original tubes of the same type. The electrometer tube is quite sensitive to very small grid voltages or variations 

in applied voltage. Any change in grid voltage varies the current 

in the plate circuit. Thus a change in current flow from C batteries 

5 and 6 also changes the grid voltage with a resultant larger change 

in the plate current of tube 2531, which is read on the zero-center 

meter. Power from C batteries 3 and 4 serves this part of the circuit.

When the circuit is adjusted for constant current through the meter 

and tube 2531 with the meter hand on zero, any variation in the circuit will cause deflection of the meter hand. Thus, light striking the
242 CONTRIBUTIONS TO GEOCHEMISTRY

phototube may be measured. Adjustment of the dark-current potentiometer so that the pointer on the zero-center meter is at zero causes 

a potential drop across the 2000-megohm resistor sufficient to draw 

current through the amplifier tube 2532, which is grounded through the 

150,000-ohm and 2000-megohm resistors, until a balance is reached 

that holds the zero-center meter on zero. Then when the switch is 

thrown to operating position the 2000-megohm resistor is no longer 

grounded but is connected to the variable voltage slide wire. Light 

striking the phototube now causes a current through the grid of tube 

2532 with resultant deflection of the meter hand. The slide wire is 

connected in the circuit so that a voltage equal to that caused by light 

on the phototube is passed to the grid of the other tube, but in the 

opposite direction, and the circuit may again be balanced. Readings 

on the slide-wire dial are relative values of this cancelling voltage. 

The sensitivity-control potentiometer selects the value of the cancelling 

voltage available, whereas the resistors in the "range" circuits govern 

and maintain proper potential ratios of this voltage.

INSTRUCTIONS FOR ADJUSTMENT OF INSTRUMENT

Arrange all parts and make all connections. Connector rings on 

all cable connectors must be tight. Use a 6-volt storage battery rather 

than a commercial power supply during the test and adjustment 

period. Be sure the instrument on-off switch is off. Check proper 

battery connections and condition of C batteries with battery test 

voltmeter, if this feature was included during construction. Turn the 

instrument switch on, set the range switch to 0.1 position, turn the 

selector switch to position for operation of transmission head, and 

close the opening to the phototube by pulling shutter slide knob all 

the way out. After a period of about 10 seconds the hand on the zerocenter meter will travel from left to right across the scale but will 

probably return to the left end of the scale. Turn the dark-current 

adjustment knob (R15) through the entire range (3 revolutions). 

The meter hand should respond at some point during rotation of knob. 

If not, then set the dark-current knob at about center of rotation range 

and change battery taps on C batteries one at a time by turning switches 

(S5, S6, S7, fig. 37) one position at a time beginning with S5 that is 

connected to battery number 1. Normally only one position change on 

switch is required to shift the meter hand to the opposite end of scale. 

The switch-tap combination that permits the meter hand to zero on the 

scale with the dark-current knob about the center of its rotation range 

is correct. The initial setting of switches should be as follows: Switch 

S5, 71/'o volt positive tap of battery 1; switch S6, Ty2 v°lt negative tap 

of battery 2; and switch S7, 7% volt positive tap of battery 3. The 

wiring diagram of battery test circuit is shown in figure 37.
MODEL '54 TRANSMISSION AND REFLECTION FLUORIMETER 243

To prevent fluorescent particles from the flux buttons and other 

foreign matter from falling through the opening onto the light-filter 

glass of the transmission unit, it is desirable to place a 2-inch square 

of glass in the bottom of the slide opening that holds the metal fluxbutton retainer. Eastman 2-inch transparency picture-slide mounts 

are quite satisfactory as they require no cutting and have little or no 

fluorescence under light of the "wavelength used in this instrument.

Check the low range of the transmission unit. Prepare several flux 

buttons of known uranium content. The writers use the shallow 7- 

milliliter platinum dish described Iry Grimaldi, May, and Fletcher 

(1952) to prepare flux buttons, although other sizes may be used, provided the button holder is modified. The size of the button from a 2- 

gram charge prepared in these dishes is 1.390 inches diameter and 0.036 

inch thick. Standard flux buttons made to contain 0.000075 and 0.0001 

milligram of uranium are suitable for this check test. Place one of 

the standard buttons in the instrument. Set the range switch to 0.1. 

adjust the dark current to zero center of meter, set the selector switch 

to transmission head, adjust the lamp current to 250 milliamperes and 

the slide-wire dial to 90 percent transmission. Open the shutter on 

the search head by pushing rod entirely in. Rotate the selectivity 

control knob (R17) until the meter hand can be set at zero. In case 

the meter hand cannot be centered by rotating the selectivity control 

knob, set this knob at one extreme end of the range, and start turning 

the slide-wire dial toward the lower end of the scale. If this does 

not allow a centering of the meter hand, then repeat the operation, but 

with the selectivity control knob set at the other extreme of its range. 

Disregard a tendency of the meter to zero, as the slide-wire reading 

nears zero on the scale, because this part of the scale is essentially the 

dark current. If necessary, repeat this test with the range switch set 

to 1.0 instead of to 0.1.

Correction of wiring on the sensitivity control or the dark-current 

control or both, by reversing the connections, may be necessary in 

case the direction of rotation of these controls is not the same as that 

of the slide wire. The lower or bottom terminal of the helipot is the 

moving contact. Uo not change this connection. When controls are 

correctly wired more light on the phototube deflects the hand on the 

zero-center meter to the left. Clockwise rotation of the dials will 

again center the meter hand.

CALIBRATION AND ADJUSTMENT OF RANGE

Turn on instrument, power source, and lamps. Allow a warm-up 

period of about 1 hour before use. Prepare sets of standard flux 

buttons of known uranium content and blanks. Three or more buttons for each uranium value are desirable, for example, 0.000025,
244 CONTRIBUTIONS TO GEOCHEMISTRY

0.00005, 0.000075, 0.0001 milligram of uranium and blanks. Switch 

to the transmission unit and set the range for 0.1. Place a 0.0001- 

milligram button in position. Adjust dark current to zero on dial with 

shutter on search head closed (pull knob full out). Turn the slide 

wire to read about 90 on scale. Open the shutter by pushing knob all 

the way in. Zero the center meter again by rotating sensitivity control knob. If this cannot be done, rotate slide-wire knob until the 

meter hand centers. In case the button contains too much uranium 

to be read on the 0.1 range, switch to the 1.0 range and obtain a reading from the slide-wire dial. The black-light lamp current may be 

adjusted to give either more or less light intensity as desired, but it 

should not be operated at less than 200 milliamperes. All buttons 

should be read when the light intensity is exactly the same. Obtain 

readings on all standard buttons and graph the machine readings 

against the uranium content. This should establish the low range of 

the instrument. A plot of data similar to that obtained by following the preceding instructions is shown in figure 42. From this 

data a permanent reference standard may be prepared. Acetate film 

0.005 inch thick with matte surface on only one side is quite satisfactory for preparation of a low-value permanent standard. A disk 

of this material, cut to fit the button holder, and masked to attain 

the desired fluorescence value by covering the film with a copper disk, 

approximately y16 -inch thick, bored to remove a portion of the center, has been very stable with little or no change in fluorescence detectable over a period of 9 months. When preparing the cooper 

mask it is convenient to start with a %2 -inch hole in the center and 

the disk scribed with concentric rings about V16 -inch apart. Place 

the standard flux button of desired value that is to be the upper limit 

of range for a particular scale setting in one slide opening. The 

masked standard is placed in the adjacent slide position so that they 

may be read alternately. The hole in the mask is then enlarged with 

a rat-tail file until the desired reading is obtained. Filing of the 

hole must be kept centered by following the scribed rings as a guide. 

When completed the film may be fastened permanently to the bottom 

edges of the mask with transparent tape. One side of the film will 

fluoresce differently from the other, therefore the standard must be 

positioned the same for all readings.

When the low range of the instrument has been established and permanent standard prepared for the 0.1 setting of the transmission unit, 

the range of the 1.0 scale may be established as follows: Balance the 

dark current and set the slide wire to read 100 percent transmission for 

the fluorescence value of the permanent standard on the 0.1 range. 

Change the range switch to 1.0. If the ratio of the 0.1 switch is correct, 

the slide-wire dial readme; should be 10. If the hand on the center
MODEL '54 TRANSMISSION AND REFLECTION FLUORIMETER 245

0.000025 O.OOO05O O.OOOO75 0.000100 

URANIUM, MILLIGRAMS

TRANSMISSION TYPE UNIT, RANGE 

O I ADJUSTED AS SHOWN IN CURVE 2

URANIUM, MIU-IGRAMS

FIGURE 42. Change of range and sensitivity of low scale available within range of 

sensitivity control without other changes in instrument.

meter does not read zero with the slide-wire reading 10, an adjustment 

of resistors is indicated. Either increase or decrease the values of 

R9 a, b (figs. 3-i, 35) by 10 ohms to determine whether an increase or 

decrease in resistance is required. The exact resistance value required 

to give the desired ratio must be determined experimentally. Eepeat 

the above test until the proper ratio is attained within the limit of 

error of reading the dial. Be sure machine has warmed up and darkcurrent balance is correct and stable when range ratio is 10 to 1.0. If 

the permanent standard was calibrated to read 100 percent- transmission, equivalent to 0.0001 milligram uranium on the 0.1 scale, then the
246 CONTRIBUTIONS TO GEOCHEMISTRY

1.0 scale should be very nearly 0.001 milligram uranium for a slidewire setting of 100 percent transmission. However, for precise work 

empirical curves should be prepared using flux buttons of known 

uranium content because of errors inherent in the method and possible 

instrument error.

The reflection unit is independent of the transmission unit and must 

be calibrated separately. A fluorescent glass standard of greater brilliance than the standard used in the transmission unit may be prepared 

from a suitably masked 2-inch square Corning glass no. 3750. The 

range of fluorescence may be adjusted over rather wide limits as desired. However, the range of the sensitivity control knob, black-light 

intensity, and characteristics of tubes in the instrument limit and control the working range. It may be desirable to obtain several tubes of 

each number, particularly no. 2532, so that the search-head assemblies 

may be tested for range and performance. The writers' experience indicates that changing from the search head of the transmission unit 

to the search head of the reflection unit requires 110 change in the rest 

of the instrument, such as changing battery taps, etc. If a particular 

tube combination requires such changes in operation, then the faulty 

tube must be located and replaced.

The calibration of the reflection unit may be made so that the working range of uranium fluorescence extends the range of the transmission unit. However, the writers prefer to set the high-value glass 

standard to read 100 percent transmission on the 1.0 scale of the reflection unit for the maximum amount of uranium usually expected in 

routine work. Then the 0.1 scale extends the working range down to 

lower values. Such an arrangement results in a highly desirable overlap of the reflection and transmission ranges. Setting the reflection 

unit to read a definite high value on the 1.0 scale also permits one to 

control the slope of the high standard curve and results in greater 

sensitivity and accuracy for determinations in the high range. In case 

the fluorescent glass standard, when masked, is still too brilliant for a 

reasonable calibration, the intensity may be reduced by placing a wire 

mesh over the light filter or by changing the primary filter. The 

following Corning filters may be used: nos. 5840, 5874, and 5860 that 

pass 55, 50, and 21 percent of black light of 365 millimicron wavelength, respectively.

DISCUSSION

The fluorimeter described here has a sensitivity equal to or better 

than that of several fluorimeters of different design that have been 

tested under working conditions at the Denver, Colo., laboratories of 

the Survey. The working range for concentrations of uranium in the 

fused-flux wafers is unusually advantageous for laboratories analyzing different types and grades of samples. Analysis of samples
MODEL '54 TRANSMISSION AND REFLECTION FLUORIMETER 247

containing traces, as well as samples of ore-grade materials, can be 

accomplished without resorting- to unusual sample size, large dilutions, or great variation in aliquot size. The low-voltage circuit 

of this instrument, about IS volts maximum with most of the circuit 

operating at 6 volts or less, tends to minimize leakage caused by moisture, dust, and fumes, with resultant stability and reliability of operation under adverse conditions. Provision for u*e of a desiccant, 

in the amplifier unit and phototube housing when the instrument is 

used under conditions of high relative humidity will aid stability 

of measurements made under such conditions.

Figure 4-2 shows a calibration curve for the transmission unit of 

the Model '54, set to read on the 0.1 range. Points B and C, curve 1, 

show readings of DO and 51.5 on the slide-wire dial for uranium values 

of 0.0001 and 0.00005 milligram uranium, respectively. This curve 

is similar to the range that will be obtained if the instrument is calibrated as described. Also shown in figure 42 are curves 2, 3, and 4 

that demonstrate different settings of sensitivity made possible within 

the range of the sensitivity control knob. No changes in the instrument are required except rotation of the sensitivity control to a 

different part of its range. Point (\, curve 2, reads 71 for the 0.00005 

milligram uranium button, but this same button may be read as 100 

(On, curve 3) by merely adjusting the sensitivity control knob. 

Likewise points D. curve 3, and D1( curve 4, show different settings 

that may be assigned a flux button containing 0.000025 milligram 

uranium.

Thus the top range of the low scale on the o.l setting may be 

varied from 0.000075 to 0.000025 milligram uranium by changing only 

the setting of the sensitivity control knob (figure 42). This change 

in sensitivity also changes the blank readings from 10 to 2o but affords 

a good working curve of almost any desired slope for accurate work. 

This illustration does not. cover the full range of settings possible on 

the range of the sensitivity control adjustment but does demonstrate 

the versatility of the instrument.

Figure 43 shows the stability of the instrument and the phototube when the temperature inside the phototube housing was raised by 

heating the exterior to cause a temperature change in the range of 

28° to 40° C (82.4° to 1()4.0°F). Normal changes in temperature 

have little or no effect on the precision of uranium determinations 

made with this instrument.
248 CONTRIBUTIONS TO GEOCHEMISTRY

OO-W MAZDA LAMP APPLIED TO SEARCH HEAD

TIME-HOURS

LEGEND

A- TEMPERATURE °C INSIDE SEARCH HEAD, AS HEAT WAS APPLIED.

B- ROOM TEMPERATURE °C.

C- VARIATION OF SLIDE-WIRE DIAL READINGS OF GLASS STANDARD AS TUBE WAS HEATED.

D- DIVISIONS DRIFT OF POINTER ON ZERO-CENTER METER WHEN READING GLASS STANDARD.

E- DARK-CURRENT DRIFT DURING HEATING PERIOD (SPECIAL SCALE ON DARK-CURRENT KNOB TO

ENABLE MEASUREMENT). 

F- DIVISIONS DRIFT OF POINTER ON ZERO-CENTER METER WHEN SET ON DARK CURRENT.

FIGURE 43. Effect of temperature change (28° to 40° C.) on stability of phototube and 

reproducibility of instrument readings.

LIST OF PARTS FOR MODEL '54 FLUORIMETER

Code

Bl-6. 

B7___

B10_

Ml.

PI, P2.

Figure no. Item and description 

35, 38 Batteries, radio C, 7Y2 volt.

36 BattenT , 6 volt, storage, automobile type, 120 

ampere-hour capacity or larger. Not needed 

if commercial-type power source is used. 

36 Batteries, five 1}4 volt, radio plug-in type. 

41 Batteries, three no. 6, \% volt, dry cells. 

41 Batteries, eleven no. 6, I,1/2 volt, dry cells. 

35 Common ground. 

31 (g), 35 Milliammeter, Beckman DU, zero-center

(range unknown).

38, 35 Plugs, Amphenol no. 79-05 M, heavy-duty 

radio connectors.
MODEL '54 TRANSMISSION AND REFLECTION FLUORIMETER 249

Code 

P3 -----

Rec 1, 2, 3. 

Rec 4-____ 

Rec 5..---

R2_ 

R3- 

R4. 

R5

R6b 

R7a 

R7b

R8b

R9b__. ... 

R10- .- 

Rlla __ .

R12_

R13a.

R13b

R16. 

R17. 

R18. 

R20-

R23_ 

R24_ 

R25_

Sl. 

82.

53.

54.

55.

urf no. 

41 

36 

38, 35

41

36

32, 35

32, 35

32, 35

32, 35

32, 35

34, 35

34, 35

34. 35

34, 35

34, 35

34, 35

34, 35

34, 35

34, 35

34, 35

34, 35

34, 35

34, 35

34. 35

34, 35

34, 35

34, 35

34

34,

34,

35

35

36

36

36

36

41

41

41

41

J(f m and df; 

Plugs, polarized, to fit receptacle 4. 

Plugs, polarized, to At receptacle a. 

Receptacles, Amphenol no. 79-P05F, heavyduty radio connectors. 

Receptacles, three wire standard type to fit

polarized plugs.

Do.

Resistor, 39 ohms, 1 watt. 

Resistor, 47 ohms, 1 watt. 

Resistor, 1 megohm. ^2 watt. 

Resistor, 150,000 ohms, '2 watt. 

Resistor, 2,UOO megohms (Bnckman). 

Resistor, 2.7 ohms, 1 watt. 

Resistor, 22 ohms, 1 watt. 

Resistor, 4.7 ohm», 1 watt. 

Resistor, 120 ohms, 1 watt. 

Resistor, 27 ohms, 1 watt. 

Resistor, 470 ohm?*, 1 watt. 

Resistor, 27 ohms, 1 watt. 

Resistor, 4.7 ohms, 1 watt. 

Resistor, 15 ohms. 1 watt. 

Resistor, 39 ohma, 1 watt. 

Resistor, 560 ohms, 1 watt. 

Resistor, 150 ohms, 1 watt. 

Resistor, 820 ohms, 1 watt. 

Resistor, 120 ohms, 1 watt. 

Resistor, 68 ohms. 1 watt. 

Resistor, 100 ohms. 1 watt. 

Relipot, 300 ohms, 3 revolution, Beckman

model C, dark-current adjustment. 

Slide-wire disk. 100 ohms. Beckman D!J (percent transmission). 

Heiipot, 200 ohms. 10 revolution, Beckman

model A (sensitivity control). 

Grid to plate resistor. 100 megohms, Beckman. 

Resistor*;, 56 ohms, 1 watt. 

Resistors, 133 ohms, 1 watt. 

Resistors, 30 ohms, 1 watt. 

Resistors, 16 ohms. 1 watt. 

Resistors, 40 ohms, 4 watt. Variable Glarostat. 

Resistors, 10 ohms, 10 watt. 

Resistors, 40 ohm>. 10 watt. 

Resistors, 75 ohms. 10 watt, adjustable, set at

60 ohms. 

Switch, range selector, rotary cermaic, two circuit, two position. 

Switch, head selector, rotary ceramic six circuit, two position. 

Switch, battery on-off. rotary ceramic, four

circuit, two position.

Switch, dark current, in phototube head. 

Switch, tap, battery no. 1. rotary ceramic, one

circuit, four position.
250 CONTRIBUTIONS TO GEOCHEMISTRY

Code Fir/tire rtt>. Item and description 

S5____________ 31 fj), 37 Switch, tap, battery no. 2, rotary ceramic, one

circuit, five position. 

S7-_-_-------- 31 (k). 37 Switch, tap, battery no. 3, rotary ceramic, one

circuit, four position.

S8_.__________ 31 U), 37 Switch, battery test, rotary ceramic, two circuit, eight position. 

S9____________ 36 Switch, battery change-over, 6-7)2 volt, rotary

ceramic, six circuit, two position. 

S10___________ 41 Switch, lamp start, 1 ampere, 125 volt, two

circuit, momentary contact, push to close

circuit.

Cable, 5-conductor, shielded, rubber covered. 

Sll_---------- 41 Switch, on-off, DPST toggle, 3 ampere, 125

volt, bat handle. 

S12___________ 41 Switch, on-off, SPST toggle, 3 ampere, 125

volt, bat handle.

VI__________ 32 (E), 35 Phototube, Beckman no. 2342-1, blue sensitive, 220-625 m/t. 

V2__________ 32 (A), 35 Electrometer tube, Beckman no. 2532, Sylvania no. 1229. 

V3____________ 34,35 Amplifier tube, Beckman no. 253, Sylvania

no. 1229. 

F_____________ 41 Fuse, 1 ampere, 3 AG, and chassis mounting.

P. L__ ________ 41 Pilot light, NE51, with resistor socket.

Tl____________ 41 Transformer, 115 volt, 60 cycle, primary; 50

va, 24 volt, secondary. 

T2__________ 41 Transformer, 115 volt, 60 cycle, primary, 35

va, 24 volt, secondary remote-control type. 

Rect !________ 41 Rectifier, full wave bridge, 25 volt a-c, 20 volt

d-c, 3-ampere, dry-plate type. 

Rect 2, 3_ _____ 41 Rectifiers, full wave bridge, 25 volt a-c, 20 volt

d-c, 600-milliampere, dry-plate type. 

M_ ___________ 41 Milliammeters, d-c, 0/500.

Lamp_________ 41 Lamp, 3 watt, 12-16 volt, d-c, fluorescent

black-light, indexing base, RP-12 bulb.

Specify 2-inch polished light filters by color specification number, otherwise a 

molded, somewhat thicker, glass will be obtained.

LITERATURE CITED

Center, E. J., 1948. topical report on the direct micro determination of uranium

using a modified fluorophotometer: U. S. Atomic Energy Oomm., AECD3006, and BMI-JDS 129. 

Davey, C. N., and Florida. C. D., 1949, The ultraviolet fluorimeter by Hilger and

Watts, Ltd.. Atomic Energy Research Establishment, Harwell, England,

AERE-EI^-R337. 

Fischer, H. V., and Pickle, C. B., 1946, an improved fluorophotometer: U. S.

Atomic Energy Comm., Mon-P-222. 

Fletcher, M. H. and May, I. 1954. An improved fluorimeter for the determination

of uranium in fluoride melts, in Grimaldi, F. S., and others, Collected papers.

on methods of analysis for uranium and thorium: U. S. Geol. Survey Bull.

1006, p. 77-83.
MODEL '54 TRANSMISSION AND REFLECTION FLUORIMETER 251

Fletcher, M. H.. May. I., and Anderson. J. \V., 1034. The design of the Model

V transmission fluorimeter. in Grimaldi, F. S. and others, Collected papers

on methods of analysis for uranium and thorium : U. S. Geol. Survey Bull.

100G, p. 93-95. 

Fletcher. M. H.. May. I., and Slavin. M.. 1954, A transmission fluorimeter for

use in the fluorimetric method of analysis for uranium, hi Grimaldi. F. S..

and others. Collected papers on methods of analysis for uranium and

thorium: U. S. Geol. Survey Bull. 1<MM>. p. S5-92. 

Galvanek, Paul, Jr.. and Morrison. T. J.. Jr.. 1954. A new fluorimeter for the

determination of uranium: I'. S. Atomic Energy Coinm.. ACCO-47. 

Grimaldi. F. S.. May. I., and Fletcher. M. H.. 1952. U. S. Geological Survey

fluorinietric methods of uranium analysis: 17. S. Geol. Survey Girc. 199. 

Jacobs, S., 1950. A study of the determination of uranium by measurement of

flluorescence: Cliem. Research Laboratory, Teddington, England. CRL AE54. 

Kanfmau, D.. Cawtillo, M . and Koskela. V.. 1950. new fluorimeter^ for the

determination of uranium: MIT models I, II. III. and IV: U. S. Atomic

Energy Conim.. MITG-A-70. 

Kelley, M. T.. Hemphill, H. L., and Collier. D. M.. 1954. An Improved fluorophotouieter for determination of uranium in fused sodium floride pellets: U. S.

Atomic Energy Comm.. C#RXL-1445. 

Kinser, C. A., 1954. The Model VI transmission fluorimeter for the determination

of uranium: r. S. G?ol. Survey Cire. 380. 

May. Irving, and Fletcher. M. H. 1954. A battery-powered fluorimeter for the

determination of uranium, in Grimaldi. F. S.. and others. Collected papers

on methods of analysis for uranium and thorium: U. S. Geol. Survey Bull.

1006, p. 07-104. 

Morton, G. A.. 3055. Recent developments in the scintillation counter field in the

United States: International conference on the peaceful uses of atomic

energy. Geneva, v. 14. General aspects of the use of radioactive isotopes:

Dosimetry, p. 24*1-259 [19501.

Price, G. R.. Ferretti. R. J.. and Schwartz. S.. 1953, Fluorophotometric determination of uranium : Anal. Chemistry, v. 25, p. 322-331. 

Yeaman, M. D., 1951. Fai;»riinetric determination of uranium in phosphoric acid:

U. S. Atomic Eenergy Comm.. DOW-65. 

Zimmerman. J. B.. 1950. The determination of uranium in ores, fluorophotometric method: Canada Dept. Mines. Tech. Surveys. Memo. ser. 114.

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