Electrical connections are made through a terminal block.
Drew, C. M., McNesby, J. R., Smith, S. R., Gordon, A. S., Ihid.,
ACKNOWLEDGMENT
Hausdorff H H “Vapor Fraotometcy,” Perkin-%lmer Corp., NO^walk, Conn., 1955. James D. H., Phillips, C. S. G., J. &hem. Soe. 1953,.1600. Patton, H. W., Lewis, J. S., Kaye, W, I., AN&. &EM. 27, 170 (1955). Phillips, C. S. G., “Gas Chromatography,” Butterworths, London,
28, 979 (1956).
The authors are grateful to Frank Sawford for assistance in the constrnction of the cell. Figure 2.
Exterior view of cell
LITERATURE CITED
Berl, W., “Physica!, Methods in Chemical Analysis p. 387, Academic Press, New *ark, 1950. Daynes, H. A,, “Gas Analysis bg Measurement of Thermal Conductivity,” Cambridge Univ. Press, Cambridge, England, 1933. Dimbat, M., Porter, P. E., Stross, F. H., ANAL.CHEM.28, 290 (1956).
The external features of the cell are shown in Figure 2. Connection with the column and sample inlet system is made with metal-glass ball-and-socket joints. Bakelite rods are tapped into the block for mounting purposes.
19.56
‘
(9) RG&-’S. A,, Bryce, W. A,, ANAL. CHEM.29, 925 (1957).
WORK done under Defense Research Board Grant 5001-10 Project No. D4450-01-10,
X-Ray Shadow Microscopy as an Aid for the Analyst Shigeto Yamaguchi, Scientific Research Institute, Ltd., 3 1 Kamifuji (Hongo), Tokyo, Japan
Figure 1. X-ray shadow micrograph of a dust containing U,O, and oxides of Figure 2. X-ray shadow micrograph of a powder of Tho, and SiO, mechonilight elements cally mixed Dark porticler correspond to U308 crystoliiter. Positive enlarged about 10 timer. for photographing, 1 minute
Exposure time Dark particles, ThOi.
Semitronrparent particle^,
Si02
crystallites containing uranium and thorium. The micrograph in Figure 1 was obtained from a powder consisting of USOS,FeXOa,Si02, A1,0,, and oxides of rare earth elements (U,O, about 3% by weight). This sample u”&sprepared from a natural uranium ore by panning. Figure 1 can be compared with Figure 2 obtained from a powder of Thoa and SiOe (quartz) mechanically mixed (Tho,, 50%). I n these micrographs, the dark particles correspond to Tho, and &Os and are distinguishable from the semitransparent particles composed of light atoms. X-ray shadow microsCOPY makes uossible the ureliminarv Of such thorium and uranium in B powdered sample.
as
ACKNOWLEDGMENT
RAY shadow microscopy was a p x - p l i e d to the determination of uranium and thorium. The microscope used W&S of the type illustrated by Cosslett and Nixon [ J . A p p l . Phys. 24,
616 (1953)l.
An electron flux from a hot filament was focused onto a target foil of tungsten by means of two separate magnetic lenses, ~ ~ voltage ~of the electrons W ~ about S 10 kv. The x-rays thus produced were rather soft, so that they were remarkably absorbed in the
The author wishes t o express his to T~~~~~~ ~ r ~d~~~ i who kindlyassistedin the present ~ work. The ltungsten foil ~ in the micro~ scope wassuppliedby W. J. O o s t e r k m h Philips Research Laborabries, t h o u g h the courtesy of V. E. Cosslett.
Filtration Apparatus for Organic Gravimetric Analysis Aaron N. Fletcher, Analytical Chemistry Branch, U. S. Naval Ordnance Test Station, China lake, Calif.
paper cannot be weighed quantitatively and organic materials would he destroyed by ignition, filtration equipment for organic gravimetric analysis i~ usually limited t o rigid-filter media. Gooch, sintered-glass, BECAUSE
and other porous-bottomed filter media fail t o give a satisfactory filtration rate when they are used for suction filtration of many materials such as oxidized products from lubricating oils, hydrolyzed cellulosic solids, and gela-
tinous precipitates [Pierson, R. H.,
AN LL. CHEM.25, 1939 (1953)]. T o separate these materials from the solution, it is often necessary to use either centrLfnga1 methods, with their inherent volume and washing restricVOL. 29, NO. 9, SEPTEMBER 1957
1387
tions, or filter media with porous walls. I t is usually possible to wash a precipitate from the sides of a porous-walled filter that mould otherwise clog a porous-bottomed filter of equivalent filtering area. Alundum crucibles with porous walls are available commercially, are chemically inert to most solutions, and can withstand high temperatures. A rubber ring is generallj: used to support the body and to supply a vacuum seal around the upper part of porouswalled crucibles, but a significant part of the crucible mall is above this seal. As there is no significant pressure differential across this exposed portion of the porouq !Tall, dissolred solids from the solution are retained within the mall, making the determination nonquantitative. Coinmercially available equipment may be easily assembled (Figure 1) that will prevent retention of dissolved solids within the walls. An Alundum thimble, commonly used for extractions, is used as the filtering crucible. It has consid-
~
P
O
W
W NNNEL R
-3Omm.00
GOOCH RU00ER TUBING
301 0Omrn.FLbT-0OTTOMED ALUNDUM EXTRACTION THIMBLE
3 6 m m . l D FILTER TUBE 160mm.
I
t'
VACUUM
Figure 1.
Filtration Apparatus
erably more filtering surface than nonporous-walled filters of the same volume capacity and more filtering surface than the largest Alundum crucible listed in most chemical catalogs. With normal operation, the walls of the thimble are kept dry by the powder funnel to about 1 cm. below the bottom of the vacuum seal. The rapid passage of air between
the bottom of the vacuum seal and the top of the wet portion of the wall is usually sufficient to prevent creepage of most liquids up to the seal. If the upper portion of the thimble is accidentally wet by the solution, there is still some pressure differential to the top of the thimble that allow even this region to be slonly washed free of diqsolved solids. After 13 t h k b l e s (30 X 80 mm. Alundum, porosity Rd 98) had been washed with 30% acetic acid and acetone, and dried under vacuum a t 100" C., they shoFed a n estimated standard deviation of 0.3 mg. weight change. Firing for 30 minutes a t 725' C. gave an average weight loss of 0.4 mg. with an estimated standard deviation of 0.5 mg. for seven thimbles. The apparatus in Figure 1 has been used successfully for over a year and has proved particularly advantageous in the gravimetric determination of a mixture of an inorganic and an organic product.
Device for Varying Burner Height in Beckman Flame Photometer Irving May, Henry Kramerl, and Edward
L.
Curtis, U. S. Geological Survey, Washington 25,
D. C.
x photometric work it is Iemission sometimes desirable t o measure the of an element in different parts FLmE
of the flame in order to evaluate the conditions for optimum sensitivity and minimum interference. The burner of a Beckman flame photometer is in a fixed position, and changes in flame focus are made by adjusting the mirrors. This is a tedious and not easily reproducible adjustment. An attachment has been built for reproducibly raising or lowering the Beckman atomizer-burner. Different parts of the flame can thus be brought into focus on the slit without changing the mirror adjustment (Figure 1). Parts F and B are the original Beckman burner and burner mounting block. The two pins are removed from the housing mounting block (not shown in figure) and the block is drilled for two 6/32 Allen cap screws, so that C can be mounted on the block with Allen screws in the position originally occupied by B. During assembly of the apparatus, the burner is shifted to compensate for its displacement in the new mounting. Two end plates, G and G', are separated by two 3/16-in~hrods, E and E'. Present address, Sew Brunsmick Laboratory, U. s. Atomic Energy Commission, Box 150, New Brimswick, X. J. 1388 *
ANALYTICAL CHEMISTRY
B E C ~ M A N ATOM I ZER-BURNER I
1, I
1
/Ill
'A DSJCURSET WI N G
Sect.*
Figure 1
MATERIAL' B R A S S
The rods have a shoulder and are threaded at each end. screw raises or lowers A 21/rinch the burner. It fits into a 3/le-inch hole that is drilled in the burner block, B; a 4/40 tapped hole is cut in the block for a setscrew which retains the adjusting screw while permitting it to rotate freely. Slots, are cut on opposite sides
of the mounting block. C is silversoldered to rod E. The two locking nuts are adjusted to prevent the burner from being lowered beyond a level where the capillary will not clear the sample cell. The height of the burner can be determined and reproduced with the aid of the scale, D , which is screwed to the back of the end plates. PUBLICATIOK authorized by the Director, U. S. Geological Survey. Work completed as part of a program conducted by the U. S. Geological Survey on behalf of the Division of Raw Materials, Atomic Energy Commission.
