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of mercury, as, for example, spraying it into a washing tower. In this case about a 40-mesh glass should be used. An extremely rapid filtration is obtained with the delivery of a mercury cloud, the particles of which are individually barely visible. While not so universally applicable as the method described by Kirk, Craig, and Rosenfels (d), this method should be of considerable value in solving many special problems arising in the research and analytical laboratory.
CHEMISTRY
Vol. 7, No. 2
A Simple Inexpensive Galvanometer Suspension H. ROSWELLJONES~ Chemical Laboratory, Johns Hopkins University, Baltimore, Md.
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N T H E course of recent work it was found necessary to insulate thoroughly a high-sensitivity galvanometer (Leeds (1) Kirk, P. L., Mikrochemie, 14,1 (1933). & Northrup Co., Type HS) from all mechanical shock. (2) Kirk, P.L., Craig, R., and Rosenfels, R. S.,IXD. EN^. CHEM., This was accomplished with the modified Julius suspension Anal. Ed., 6, 154 (1934). shown. The heavy soapstone slabs, A , are separated by the (3) Miller, R.P.,and Kirk, P. L., Mikrochemie,14,15 (1933). threaded rods, B. The slabs are free to move vertically and can be held in any position by means of the lock nuts, C. RECEIVED February 4, 1935. Aided by a grant from the Research Board of the university of California. The galvanometer, G, rests on a sheet of tin plate, L, which is s e t o n t h e base block. T h e t i n Use of Sintered Glass Disks in plate is grounded t h r o u g h a flexible Distillations lead and acts as an electrostatic shield M. MATTIKOW, Columbia University, New York, N. Y. for the galvanometer. The legs of the HE writer has had occasion to extract material with galvanometer r e s t large volumes of volatile organic solvents. When the upon small blocks extract, containing a high percentage of oily and other matters, of paraffin. was concentrated by distilling the volatile organic solvents, The whole is supconsiderable difficulty was ported by the three experienced in preventing eyebolts, E, spaced bumping. The common ex- a t the corners of an pedients, such as putting in isosceles t r i a n g 1e. glass beads, pieces of por- These are connected celain, pumice, and capillary through the springs, tubing, were found to be of F , to the supporting dog chain, D. little aid. The incidence of bump- All electrical connecing was completely elimi- tions are made by wires dipping into 30-cc. beakers containn a t e d b y i n h o d u c i n g a ing mercury, mounted on small paraffin blocks placed on the sintered filter disk as shown base block. Mercury is used because it allows the use of large in t h e d i a g r a m . (Such lead wires and a t the same time prevents the transmission of glass tubes are sold com- any mechanical disturbances through the leads to the galmercially under the name of vanometer. It was found that when the galvanometer was “gas distribution tubes with enclosed in a large metal compartment with a glass door, the fused-in fritted-glass filter absolute lack of air currents made the customary damping FIGURE 1 disks.”) A i r , F a s s e d vanes of the Julius suspension unnecessary. The metal of the through the tube, is broken box made an efficient electrostatic shield when grounded. In operation the upper soapstone slab is raised or lowered up into many tiny bubbles which keep stirring the solution, thus preventing local superheating. When the solvent has until the center of gravity of the system is a t the mirror, M , been almost all distilled and a fresh charge of extract put in, the of the galvanometer. Under these conditions the system whole is effectively mixed by allowing air to be blown more will rotate about this point and the mirror will be a t the point rapidly through the solution, thereby obviating the necessity of least motion of the system. Then, with the springs abof disengaging the flask from its clamped position and rotating sorbing all vertical impulses and the chain the horizontal or shaking to effect mixing. Several fresh charges have been ones, with the system once in equilibrium, the mirror will not added to the original one by this method without disturbing be disturbed by outside mechanical forces. This condition the distilling flask. Despite the increasing concentration of has been realized in actual operation. This suspension has proved satisfactory in measuring deoily matters, there was no bumping a t any stage. In certain cases where air is not desirable because it may flections of 0.1 mm. on a scale placed a t l m. with several oxidize the extracted matter, or induce chemical change, an large electric motors operating very close to the galvanometer. inert gas like nitrogen or carbon dioxide may be used. RECEIVED February 25, 1935. It is suggested that heated gases be used to distill the sol1 Present address: The Atlantic Refining Go., Franklin, Pa. vents instead of an outside source of heat. Steam distillation also has been carried out smoothly and effectively by leading the steam through the sintered glass disk. LITERATURE CITED
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RECEIVED January 12, 19351
