PRESENCE OF ARSENIC. 605 
About the time I was making these experi- 
ments, I communicated my ideas to my friend, 
Dr. Haworth, of this town (Bolton); and, in 
several weeks afterwards, he informed me that a 
number of the Lancet, just published, stated that 
M. Orfila had been describing in France different 
processes whichmight be adopted in distinguishing 
of which of the two metals a crust consisted, and 
amongst them he mentioned the application of 
heat ; I, however, did not get to see the Lancet, 
nor did I learn the particulars of what was said 
regarding the application of heat, but about the 
beginning of this month my friend kindly put into 
my hands the British and Foreign Medical 
gaseous matter be generated during the process. This, if true, 
would have been exceedingly favourable to my mode of dis- 
tinguishing between arsenic and antimony ; but the assertion 
is not to be relied upon. I took a narrow tube, sealed at one 
end, nearly filled it with cold silex in very fine powder, 
which had only a few minutes before been exposed to a red 
heat, and then pushed into it, through the powder, a slip of 
glass, having crusts of antimony upon it. By this manage- 
ment the metal was secluded from air of every kind, and 
confined in a medium for which it possessed no chemical 
affinity. Thus prepared, the tube was immersed to about half 
its depth in boiling oil, and the antimony volatilized, and left 
that part of the slip surrounded by the hot oil in as short a 
time as if atmospheric air had been present. 
I submitted a slip having arsenic upon it, to a similar 
experiment, and obtained a corresponding result. 
