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ANALYTICAL CHEMISTRY
mensions as the electrode to be Dreuared. The rod. with a center
the jig;th, chuektightened, and the hole drilled:
c I Inch
Figure 2.
3
Drilling Jig
ed by the preparation of 108 electrodes. Of mese, only one was broken and this one was suspected to have been cracked during the cutting t o length. There n.as no tristing of the electrode during drilling and no marlis were produced on the outer surface. The time required far processing one electrode, including cutting t o length, facing the end, and drilling, mas 2 minutes.
shelim&mial is Lucite. Thearmsof the shell aremachined normal to their bores and are sealed by Teflon disks retained by screwed caps of Lucite. In operation, materials of differentcolors are blended, as judgcd by the eye, in a very few minutes. No separation of the mat,erial mass is noted except for the planned division per revolution. Blending times for specific applications must be determined, but usually overnight run8 are sufficient. The unit operates without attention, and blends with infinite patience. It has proved to be a useful laboratory tool, superior to rolling tumbling counterparts.
ACKNOWLEDGMENT
Magnetic Stirrer for Cryoscopic Determinations. Joseph L. Rabinowita, Department of Physiological Chemistry, University of Pennsylvania, Philadelphia, Pa.
The author n-isbes to express his appreciation t o Eugene Berg and A. E. Rymer for their assistance in testing aud fabricating the jig, and to The University of Texas Research Institute for a grant which made this work possible.
HE diagram represents an all-glass magnetic stirrer that has Theen successfully used in this laboratory. Constructed by James Graham, it proved satisfactory in the cryoscopic determination of molecular weights a t higher temperatures.
Twin-Shell Micrablender for Powders. Louis E. Owen, 117 Gorgas Lane, Oak Ridge, Tenn. T IS
often desirable in a spectrochemical laboratory to be able
I to mix powders very thoroughly for the preparation of stand-
ards or analysis matrices. The standard technique far this aperrttion is grinding in a mortar. Such grinding is s laborious process, requiring attention even when power-driven mortar and pestles are used. A concomitant problem is the contamination of a sample with the elements of the mortar material. This is serious in the case of extremely hard materials such as beryllium carbide. Suoh materials, however, may often be powdered in Plitttnertype mortars without marked introduction of foreign elements. Crushed samples of this genre usually can be screened through 8. silk sieve and the dusts (
