PRESENCE OF ARSENIC. 603 
and then hermetically sealed, with a blow-pipe 
flame, the orifice of the tubes. Thus arranged, 
the tubes enclosing the slips were immersed to a 
little more than the depth of the coated part of 
the slips, (25 inches, the length of the tubes 
being about five inches,) in a bulb containing 
rape oil in a state of ebullition. In one minute 
the arsenic had entirely disappeared from that 
part of the slip surrounded by the hot oil; but the 
antimony did not entirely disappear before the 
expiration of seven minutes. Other subsequent 
experiments of the same kind, corroborated the 
conclusion arrived at in this instance, that a very 
thin film of antimony was very much longer in 
evaporating away, by the heat given by boiling 
oil than a very thick crust of arsenic. The next 
object was to endeavour to find a temperature 
lower than that of boiling oil, at which arsenic 
would entirely volatilize, and antimony remain 
permanently fixed; and about the beginning of 
November I made numerous experiments, similar 
to the above, but taking care that the oil from 
which the heat was communicated was kept at a 
temperature ranging from 490° to 500°, a ther- 
mometer being all the time kept immersed in it. 
In some instances thick crusts of arsenic were 
entirely volatilized in about fourteen minutes, 
