684 



SGIENGE. 



[N. S. Vol. VII. No. 176. 



pecially the fact that many outbreaks of typhoid 

 fever have been traced directly to an impure 

 milk supply, the Medical Society of the District 

 of Columbia has endeavored to introduce a good 

 milk by appointing a committee that should 

 supervise a dairy and laboratory which was to 

 be conducted on thoroughly hygienic principles. 

 Such a dairy has been established and all possible 

 precautions are observed. The milk is obtained 

 from healthy tuberculin-tested cattle. These 

 are kept in a well-ventilated, clean stable with 

 a cement floor. Before milking the animals are 

 carefully cleaned and curried, and taken into a 

 smaller building designed for a milking room 

 and kept as far as possible free from dust. The 

 milk is immediately passed through a separator 

 and cooled to about 45°. It is then brought to 

 the bottling laboratory in cans, when it is placed 

 in thoroughly clean sterilized bottles, which are 

 sealed with paraflSued paper caps. This milk is 

 called sanitary milk, to distinguish it from other 

 milk which is still further improved by pasteur 

 ization. Ordinary milk may contain from 60,- 

 000 to two or three millions of bacteria per cc. , 

 whilst by the above method a milk has been 

 obtained which contained only from 1,200 to 

 3,000 bacteria per cc. 



Dr. Hillebrand read a paper on ' The Colori- 

 metric Estimation of Small Amounts of Chro- 

 mium with Special Reference to Kocks and 

 Minerals.' The time required for the separa- 

 tion of chromium from certain other constituents 

 which have likewise to be determined in rock 

 and ore analysis is very considerable ; the 

 amounts in question are often extremely small, 

 and the separations are, therefore, more or 

 less imperfect ; hence, a rapid and accurate 

 method for these small amounts is very much 

 needed, and seems to be fully afforded by a 

 comparison of the color of an alkaline solution 

 of the chromium as chromate with a similar 

 solution containing a known amount of chro- 

 mium. The method was thoroughly tested 

 with prepared chromium solutions whose con- 

 tents ranged in amounts from 1 mg. to 7.5 mg. 

 counted as CrjOa, in varying dilution, though 

 the figures given by no means represent the 

 limits of the method. The standards employed 

 contained KjCrOi, corresponding to .1 and .2 

 mg. per cc. , respectively, of CrjOj, and in mak- 



ing the determinations were always diluted to 

 agree with the purposely made weaker test 

 solutions. The maximum and minimum devia- 

 tions from the truth were -|-.32 mg. and — .26 

 mg. ; the average error being a little less than 

 + .02 mg. 



The method was given a severe practical test 

 by adding to several grammes of an iron ore, 

 and also to a silicate, known amounts of chro- 

 mium and subjecting the mixture to fusion with 

 sodium carbonate and potassium nitrate, pre- 

 cipitating PjOs, V3O5 and CrOa from the aqueous 

 extract with mercurous nitrate, igniting the 

 precipitate, fusing the residue with sodium 

 carbonate and thus obtaining a small bulk of 

 highly colored solution. The results were 

 equal to those of the preliminary tests and 

 show the method to be highly accurate for small 

 and moderate amounts of chromium. "When 

 there is enough chromium in a sample to give 

 a sufficiently colored extract of the first alkali 

 fusion the color comparison may be made at 

 once with this solution and thus much time may 

 be saved. Maganese, however, must be thor- 

 oughly removed, most quickly by reduction 

 with methyl alcohol. The glasses used by the 

 author were shown and the simple precautions 

 for securing proper illumination were described. 

 For amounts less than .1 mg. it is best to use 

 Nessler tubes. 



Mr. Tassin exhibited specimens of products 

 obtained in Moissan's electric furnace consist- 

 ing of carbides of aluminum, boron, iron, 

 cobalt, cerium and calcium, the elements 

 molybdenum, uranium, tungsten, titanium and 

 chromium and a piece of iron containing a 

 diamond. The high temperature which it is 

 possible to obtain with this furnace was illus- 

 trated by a specimen of fused lime. 



Dr. Bolton presented a postscript to his paper 

 on ' Earl J' American Chemical Societies,' which 

 he read at the meeting held on April 8, 1897. 

 He called attention to a club of German chem- 

 ists which was organized in New York in the 

 winter of 1863-64. The president of the club 

 was Dr. Friedrich Hoffman and prominent 

 among its members were Ferdinand F. Mej'er, 

 M. Alsberg and Isidore Walz. 



William H. Keug, 



Secretary. 



