292 



SCIENCE 



[N. S. Vol. XXVII. No. 686 



same results with citric acid failed, the 

 urine showing, if anything, a slight in- 

 crease of acidity. Even a half normal 

 solution of citric acid produced the latter 

 effect. When taken internally, the acids 

 mentioned acidify the urine. Thus it ap- 

 pears that when, for instance, sulphuric 

 acid is taken in through the skin quite a 

 different physiological effect is produced 

 from that found when the acid is taken 

 into the digestive tract. 



The work demonstrates clearly that liv- 

 ing membranes act differently osmotically 

 from dead ones, and that different living 

 membranes may act very differently indeed 

 toward some substances and yet much the 

 same toward others. Whether a substance 

 will be absorbed or not depends upon its 

 specific nature and that of the membrane. 

 The results of the experiments are a step 

 forward toward a better understanding of 

 ■the processes of absorption and secretion. 



On the Befra-ctive Indices of Absolute and 

 of Aqueous Alcohol: Launcelot An- 

 drews. 



Absolute alcohol prepared by the use of 

 calcined marble has the same density, the 

 same refractive index and the same critical 

 temperature of solution as that which has 

 been dried by the use of metallic calcium 

 or of magnesium amalgam. 



The observations of Caismer to the effect 

 that the critical temperature of solution of 

 absolute alcohol in kerosene is the best 

 criterion of the dryness of alcohol is fully 

 confirnied. 



Absolute alcohol was found to have the 

 following constants: 



Density 25V40° 0.78510 0.00002 



Zeiss immersion refractometer, 



85°.30 0.02 at 25° H 

 Index of refraction .... 1.35941 0.00002 25° H 



A table is presented, showing the re- 

 fractive indices by the Zeiss immersion 



refractometer readings of aqueous alcohols 

 for each per cent, of water from to 30. 

 It is shown that aqueous alcohol has a 

 maximum refractive index of 1.363315 

 0.000010 at 20.7 per cent, of water, cor- 

 responding to the formula. 



On the Refractive Indices of Ether Alcohol 



Mixtures: Launcelot Andrevps. 



It is in general possible to determine the 

 concentration of the solution of an organic 

 substance in an organic solvent more rap- 

 idly by an observation of the refraction 

 index than by the density. This is emi- 

 nently so when the observation is made by 

 the Zeiss immersion refractometer, which 

 is frequently possible when the solvent is 

 ether, alcohol or especially methyl alcohol. 



Having occasion to determine the ether 

 content of the mixtures named in the title 

 by wholesale, a table was constructed show- 

 ing the Zeiss constants for mixtures of 

 absolute ether with aqueous (91 per cent.) 

 alcohol, over the range from 100 to 84 per 

 cent, of ether. 



This table is given in the paper, together 

 with a description of the experimental 

 Avork on which it is based. 



The Latent Heat of Vaporization of 

 Methyl Silicate: Louis Kahlenberg and 



EOBERT KOENIG. 



Methyl silicate was prepared by treating 

 silicon tetrachloride with absolute methyl 

 alcohol. The pure product was found to 

 possess a latent heat of vaporization of 

 46.48. Its specific heat between 23° and 

 115° C. was found to be 0.5011. The liquid 

 boiled at 121° C. under 750 mm. pressure. 

 The latent heat of silicon tetrachloride was 

 redetermined and found to be 36.1. The 

 value determined by Andrews was 37.3. 

 The specific heat of silicon tetrachloride 

 was found to be 0.1904 between 40° and 

 25° C. This agrees well with the value 

 found by Eegnault. 



