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.
499
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.
I>$,;.I
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
