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T H E J O U R N A L OF I N D U S T R I A L A X D ENGINEERING C H E M I S T R Y
A new text is desirable which will list mineral colors seen under t h e new illuminator. The writer desires t o t h a n k t h e above-mentioned gentlemen and many others who have been kind enough t o make suggestions and send photomicrographs. A NEW CONDUCTIVITY CELL By Frank E. Rice DEPARTMENT OF CHEMISTRY, CORNELLUNIVERSITY, Received August 6 . 1920
ITHACA,
N. Y .
The measurement of electrical conductivity of solutions is being more and more employed i n manufacturing operations for t h e control of processes. I n such instances a high degree of accuracy is unnecessary, since comparative results are more important t h a n absolute. The one thing necessary is a n apparatus sturdy, simple, and easy of adjustment, so t h a t a trained physicist need not be employed for its operation. At t h e present time there may be obtained on t h e market all t h e electrical parts necessary for t h e installation’of a Wheatstone bridge of such form t h a t it may be easily manipulated without any adjustment or attention. As a source of current, a 60-cycle line may be drawn upon; alternating current galvanometers were found sufficiently sensitive for practical work.
A NCW
co,uDucnvirr
CELL.
As an adjunct t o such equipment t h e conductivity cell here described may be prepared b y t h e amateur glass blower in a short time. It will be found strong and easily cleaned. I n the accompanying drawing t h e idea is diagrammatically illustrated, though t h e dimensions and particular arrangement of parts may be varied at will.
Vol.
12,
Xo.
12
A glass tube about t h e size of a n ordinary buret is used for the case. Platinum wires are blown through t h e sides of this t u b e some distance apart. Platinum bands made t o fit snugly around t h e t u b e are soldered closely t o t h e outside ends of t h e wires. The inside ends are long enough t o reach t o one end and outside t h e t u b e ; t h e inside portion of one wire is covered with small glass tubing for t h e purpose of insulation. Since t h e temperature of t h e solution in which measurement is made is usually important, a thermometer passes through t h e tube. This thermometer should be of considerable accuracy and one graduated in 0.2’ C. is suggested. This should be planned, however, t o accord with t h e accuracy desired, and will depend also upon t h e ther,mal coefficient of t h e solutions in which measurements are made. The ends of t h e tube are finally closed with rubber stoppers. The distance between t h e ’band electrodes and their size should be gaged by t h e conductivity of t h e liquid in which t h e cell is t o be used. T h a t an idea m a y be obtained of t h e constant t o be expected, t h e following result is reported on one cell which has been used. (The electrodes are platinized.) Circumference of b a n d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 mm. 6 mm. Width of b a n d . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 mm. Distance apart (inside to inside) Resistance recorded of 0.01 AT KCl a t 18’ C.. . . . . . . . . . . . . . . . . 261 ohms 0.321 Constant of cell.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The above measurement was made by holding t h e cell upright in the solution, using a 500 cc. wide-mouthed bottle as t h e container. Since the paths of current flow are wholly outside this apparatus, i t is essential t h a t t h e vessel containing t h e solution be always of t h e same dimensions in order t o insure comparative resylts. Furthermore, t h e position of t h e cell in t h e vessel should always be t h e same. These precautions apply, of course, unless t h e container is of great size.
ADDRESSES AND CONTRIBUTED ARTICLES AMERICAN PROGRESS I N THE BACTERIOLOGICAL SUGARS
By Edmund H. Eitel SPECIAL CHEMICALS Co., HIGHLAND PARK,ILL
The history of the carbohydrates.covers a brief period of time, during the last ten years of which a large part of the progress in methods of preparation is t o be found in American chemical literature, and practically all of the progress in commercial methods has been due to American ingenuity. The prime investigator in the chemistry of the rare sugars was Emil Fischer, who began his well-known researches in 1883. The first to make a reasonably direct use of the sugars in bacteriology was Escherich, who thirty-four years ago wrote one of the great bacteriological classics, “The Intestinal Bacteria of Nurslings.” By 1902, the possibilities of fermentation reactions with the carbohydrates were recognized by many bacteriologists, and at this time Martini and Lentz introduced the use of mannitol to differentiate the Shiga from the Flexner bacillus. Later intensive studies of bacillary dysentery in America by Park and 1 Presented before the Sugar Section a t the 60th Meeting of the American Chemical Society, Chicago, IIl.,~September6 t o 10, 1920.
Dunham, Hiss and Russell, and by others, differentiated by means of sugar fermentation other strains in the dysentery group, and thus the carbohydrates were established as a necesi sary aid in bacteriology. Germany was the only commercial source of supply for the rare sugars before the war. During the war the stocks of sugars on hand were in most cases soon exhausted, and the U. S. Army Medical School, and other investigators using the sugars in colon-typhoid and other important differentiations, found their work critically handicapped a t the moment it became most vital to the nation. Owing largely, however, to the researches of such men a s Hudson and his co-workers of the Bureau of Chemistry of the U. S. Department of Agriculture, and Levene and his associates in the Rockefeller Institute, methods were developed for preparing the necessary rare sugars in this country. The Carbohydrate Laboratory of the Bureau of Chemistry had been engaged since 1909 in investigating the rare sugars and their derivatives, and this work was continued during the war, and considerable quantities of various sugars were prepared. They were similarly produced a t the Rockefeller Institute, where of special interest were the researches of Levene and Jacobs, who
