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 f r o m the values thus obtained t h e vapor composition calculated. I t will bc noted t h a t t h e extrapolation was in no case greater t h a n four degrees, because t h e boiling points of these rich alcohol mixt.ures are nearly constant. In ordcr t o show t h e applicability of these curves, let i t 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 t h e composition of the vapor and the pressure under which t h e liquid is boiling. Were t h e liquid boiling a t atmospheric pressure it would have a vapor composition at 7 7.7 per cent. Vnder these conditions i t would boil at 8 2 ' . Sincc it is boiling at ~ o o *its , boiling point has been increased IS' by pressure. From t h e correction curve i t is seen t h a t 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 t h e 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., t h e pressure at t h e given. point in t h e still is 1.97 atmospheres or 1497 mm.
499
adding 0.1 cc. of milk to be tested and incubating, t h e writer found t h a t t h e time required t o match t h e colors, and t o make t h e necessary changes of tubes t o and from t h e comparator, was so great t h a t a large number of tubes could not be read each hour by t h e colorimetric method.
I>$,;.I
To make i t possible to compare a great Iiuii!her ~f unknowns with t h e standard tubes, t h e comparator of Hurwitz, Meyer and Ostcnberg' was modified as shown in t h e 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 t h e 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 t h e currents as fast as i t is poured into t h e 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 t h e 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
