Simultaneous Photography of Two Wave-Length Ranges in Spectrochemical Analysis. N. H. Nachtrieb', J. G. Conway*, E. D. Wilson', and S. Wexlers, University of California, Los Alamos Scientific Laboratory, Santa Fe, New Mexico. HE
range of wave lengths photographed a t one setting of the
Tcamera or slit of commercial spectrographs may not include
all the sensitive lines of all the elements to be determined in rare samples. Figure 1 shows a diagram of a commercially available spectrograph (A.R.L.-Dietert) modified so as to direct light from one arc or spark source upon two of the slits a t one time.
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Figure 2. Use of Two Spectrographs to Phothgraph Two Wave-Length Ranges Simultaneously '9"FL
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lines shows the slit illumination to be uniform. By this arrangement the most suitable photographic emulsion may be selected for the wave-length range of each instrument. In either method the exposure time for the two spectral ranges need not be the same, for each slit possesses its own shutter.
Figure 1. Use of Two Slits to Photograph Two Wave-Length Ranges with One Camera
The camera records the spectrum from 2250 to 4600 A. of the light which enters the first slit. A second surface mirror and an achromatic lens (9-inch focal length, 2.25-inch diameter) situated as shown on the second optical bench direct a portion of the light through the second slit. The camera receives the spectrum from 4200 t o 6700 A. of light from this slit. Rectangular diaphragms, 1.5 mm. high and 8 mm. wide, are placed a t the secondary foci of the grating on the two optical benches. The diaphragm on the second bench is displaced 2 mm. above that on the first bench, so that the spectra of the two regions are juxtaposed rather than superimposed. Eastman type I - S or 103-aF film is sensitive over the combined spectral regions; the latter offers better resolution, contrast, and speed.
T H Ipaper ~ is based upon work performed under Contract W-7405.Eng.-36 with the Manhattan Project a t the Los Alamos Scientific Laboratory of the University of California. I n will appear in Division V of the Manhattan Project Technical Series as part of the Los Alamos Laboratory.
, GOOCH CRUCIBLE
There is some compromise of speed, contrast, and resolving power when one photographic emulsion records the spectrum of the whole range 2250 to 6700 A., and this may be overcome by using two spectrographs mounted on a line facing one another. Figure 2 shows how a 45-90-45" prism may be used, together with a fairly long focus lens (25 inches) in case the optical axes of the two instruments are not in line, either laterally or vertically. The proper position of the prism is determined by visually observing the distribution of intensity along tall spectrum lines and securing it by means of a rigid mounting. Shims may be inserted beneath the prism until photometry of the full slit height
WALTER C R U C I E L.E HOLDER
1 Present address, Institute for the Study of Metals, University of Chicago, Chicago, 111. f Present address, Radiation Laboratory, University of California, Berkeley, Calif. a Present address, Institute for Nuclear Studies, University of Chicago, Chicago, Ill.
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Convenient Filter Flask. S. C. Hindin and J. Grider, Houdry Process Corp., Marcus Hook, Pa. HEN filtering with vacw u i m , removal of filtrate from the usual filter flask is rather awkward. The flask shown in the drawing, which is easily constructed from any of the larger size test tubes, is somewhat more convenient to use. When the volume of filtrate is greater than that of the tube, portions of the filtrate may be taken off without disturbing the filtration more than momentarily. I t may be similarly used when a precipitate is washed for removal of soluble salts.
