302 Intelligence and Miscellaneous Articles. 



trace of water, or to the solution of substances from the sides of 

 the receiver. 



In order to estimate the degree of influence of these various 

 causes, I first added to specimens of the same alcohol increasing 

 weights of distilled water, the resistance of which w T as nearly ten 

 times less than that of the alcohol used. I ascertained that the 

 resistance of the mixtures thus obtained goes on decreasing, and 

 attains a maximum which does not much differ from the resistance 

 of water, when there is not more than 3 per cent, of water, and 

 then increases up to the resistance of water. But a notable alte- 

 ration of composition is always necessary to produce a distinct 

 change in the resistance of the mixture. The difference between 

 the numbers cited above cannot therefore be ascribed to the small 

 quantity of water which commercial absolute alcohol might retain. 



If, on the contrary, a trace of a standard solution of chloride of 

 sodium is added, an enormous alteration is produced in the resist- 

 ances. A fall in the ratio of 1 : 0*527 is obtained by the addition 

 of a weight of salt representing 2 ,6oo,ooo * na * °^ alcohol. We are 

 thus led to attribute the variations to the absorption by the alcohol 

 of some ten millionths of salts from the vessel which contains it. 



I have, in fact, observed that the conductivity of alcohol increases 

 in glass vessels more rapidly than that of water. It may double 

 in a few hours. Absolute alcohol prepared with great care and 

 kept for two years in a closed and full glass vessel in the chemical 

 laboratory of the Ecole Normale was ten times as good a conductor 

 as commercial absolute alcohol. Burnt upon a platinum plate, this 

 alcohol coloured the flame yellow. It contained a trace of soda 

 salts from the glass. 



I endeavoured to avoid these alterations by dispensing with the 

 use of glass vessels ; and with this view I had absolute alcohol 

 collected in porcelain vessels in the manufactory of M. Billault. I 

 have observed the resistance to increase, and for the specimens in 

 question to 5*14 and 5*44 megohms at 15°. The second specimen, 

 contained in biscuit porcelain, retained a remarkable constancy for 

 several days. 



M. Delacbanal was kind enough to prepare for me, by a series of 

 distillations, alcohol at its minimum density like that which is used 

 for determining the point 100 of the new alcoholometers. Two 

 specimens of this were sent to me, one in a porcelain and the other 

 in a glass vessel. The former gave at 15° the resistance 7*031 

 megohms, the greatest I have observed ; the other, which was 

 already altered by the glass, was 2*823 megohms. A fresh specimen, 

 prepared in the same way six days after the first and kept in a por- 

 celain vessel, gave 6*899 megohms, only differing from the other 

 by -5^ of the value. Although traces of dissolved salts cannot ap- 

 preciably alter the density of alcohol, it might be desirable to distil 

 and preserve in porcelain receptacles the alcohol intended for 

 delicate chemical operations. 



I have also examined the changes which alcohol experiences 

 when its temperature varies. I found that the resistance dimi- 

 nishes in the mean by 0*0145 of its value, when the temperature is 



