Physiological effect caused by vapor of mercury. 7 
¢ 
and changes its density and refracting power, effects which do 
time in use. 
Physiological effect caused by the vapor of mercury.—We 
learn from Faraday that mercury is volatile at the freezing 
temperature in a confined atmosphere. The chemists of Hol- 
land have observed that an atmosphere becomes destructive to 
plants if it contains vapor of mercury. The same chemists 
have recognized that sulphur constitutes a sure antidote in this 
case. On repeating and confirming these experiments, Bous- 
singault found that the neutralizing effects of the sulphur lay in 
the formation of sulphuret of mercury. e plants sensitive 
to mercury resist its action and continue to flourish, if their 
leaves have just been sprinkled with sulphur. In this case the 
sulphur at the end of a month takes a dull grayish appearance, 
due to the sulphuret produced. Sulphur is doubtless a little 
volatile at the ordinary temperature, and the tension of its va- 
por is not appreciable; but the results obtained show that the 
tension is not nul; and as the densities of the two vapors are 
nearly the same, and as the equivalent of mercury is nearly 
six times that of sulphur, it is evident that one volume of sul- 
