An Improved Comparator - American Chemical Society

let it be assumed that a 50 per cent alcohol-water mix- ture is boiling at a temperature of 100o C. at some point in the lower part of a rectifying co...
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Xay,

1920

T H E J O L ' K N A L O F 1.YDUSlIU.i L ,1ND E N G I N E E R I N G C H E J I I S T K Y

curves, either straight lines or very Aat, werc extrapolated up t o t h e boiling point, and from the values thus obtained the vapor composition calculated. I t will bc noted t h a t the extrapolation was in no case greater than four degrees, because the boiling points of these rich alcohol mixt.ures are nearly constant. In ordcr t o show the applicability of these curves, let it be assumed t h a t a j o per cent alcohol-water mixture is boiling at a temperature of soo' C. at sonic point in thc lower part of a rectifying column. I t is required t o determine the composition of the vapor and the pressure under which the liquid is boiling. Were the liquid boiling a t atmospheric pressure it would have a vapor composition at 7 7.7 per cent. Vnder these conditions it would boil at 8 2 ' . Sincc it is boiling at ~ o o *its , boiling point has been increased IS' by pressure. From the correction curve it is seen that the vapor composition changes 0.524 per cent per degree. This corresponds t o a correction of 0.9 per cent. Thc correction is positive for a decrease in boiling point and is, therefore. negative for t h e case in question. Hence the vapor composition of the j o per cent alcohol a t 100' is 76.8 pe,r cent. At zooo water excrts one atmosphere pressure. I t is seen from the vapor pressure ratio curve t h a t a ,io per ccnt solution eserts 1.97 times as much, i. c., the pressure at the given. point in the still is 1.97 atmospheres or 1497 mm.

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adding 0.1 cc. of milk to be tested and incubating, the writer found t h a t the time required t o match the colors, and t o make the necessary changes of tubes t o and from the comparator, was so great that a large number of tubes could not be read each hour by the colorimetric method.

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To make i t possible to compare a great Iiuii!her ~f unknowns with the standard tubes, the comparator of Hurwitz, Meyer and Ostcnberg' was modified as shown in the accompanying illustrations.

A SIMPLE METHOD FOR THE PREPARATION OF SODIUM AMALGAM IN FLAKES' By Arthur I). Hirschfelder and Merrill C. Hart U~NIYBRSITYos MINNISUTA,MINNBAPOLIS, MINN.

Received Novcmber 28, 1919

In the course of preparation of saligenin by a slight modification of Hutchinson's method made by Xfr. Hurd,? it has been necessary for us t o use a 2 . 7 5 pcr cent sodium amalgam. This amalgam, when poured on t o porcelain plates, forms solid layers, which require a good deal of work and time t o reduce t o a powder in a mortar. We have been able t o prepare a powder of vcry finely flocculent amalgam by pouring the hot liquid amalgam slowly into a battery jar of xylene or kerosene, which is already being rapidly agitated by an elcctric stirrer. The amalgam is broken up b y the currents as fast as it is poured into the liquid and the fine flocculi settle t o the bottom. They are then dried in a current of air on a porcelain plate. When the flocculi are clumpcd they arc readily pulverized by a couple of blows with a pestle. AN IMPROVED COMPARATOR By L. H. Cooledge MLCHIO&NACRICULIVRALC O L L ~ LEAST B ~ ~ ,I.~wairrc, M z C W ~ O A N

Rereived January 12, 1920

While studying the change in hydrogen ion concentrationa of water or o i a solution of broth due to I

From the Ikpartmcnt of Fharmrcology. University of Minnesota,

w i t h the aid of funds xranted hg the United States Interdepartmeiifal Socinl Hygiene Board for Reierrch in the prevention and