604 ON DETECTING THE 
and, in other instances, crusts less thick disap- 
peared in about eight minutes ; the length of time 
required for the entire volatilization depending 
upon the thickness of the crust; but very thin 
films of antimony stood the temperature for an 
hour, without volatilization taking place in any 
perceptible degree. I next conducted similar 
experiments at a temperature ranging only from 
355° to 365°, and found very thick crusts of arse- 
nic to be volatilized in three or four hours, thin 
ones disappearing in half an hour or less; those 
formed from gas produced by acting upon zine 
with 400 gr. mea. of diluted sulphuric acid, (one 
volume concentrated acid to seven water) con- 
taining one drop of a solution of arsenious acid, 
sp. gr. 1.026, disappeared in half an hour, while 
those of antimony, apparently of the same den- 
sity, did not diminish in the slightest perceptible 
degree in twenty hours; and it did not seem 
probable that they would have diminished, how- 
ever long they had been submitted to the same 
temperature, that bemg lower than the point at 
which antimony begins to volatilize.* 
* From the eleventh edition of Dr. Henry’s Elements of 
Chemistry, Vol. II, page 81, it is to be found that Thenard 
asserts that antimony is not volatile, when exposed to heat in 
closed vessels, if atmospheric air be carefully excluded, and no 
