Operation and Tests. 49 
(d) TESTS WITH REAGENTS. 
In the examination of sulphides, arsenides, 
antimonides and related ores, the assay should 
be roasted before using a _ flux, in order to 
convert the substance into an oxide. This is done by 
spreading the substance out on a piece of charcoal and 
exposing it to a gentle heat in the O. F.. The sulphur, 
arsenic, antimony, etc., pass off as oxides in the form of 
vapor, leaving the non-volatile metals behind as oxides. 
The escaping sulphurous acid gives the ordinary odor 
of burning sulphur, arsenic acid, from arsenic present, 
the odor of garlic, selenious acid, from selenium pres- 
ent, the odor of decaying horseradish, while antimony 
fumes are dense white and have no odor. 
After the finely pulverized mineral is roasted as 
directed above, take a piece of the thinner patinum wire, 
make a loop in one end of it about the eighth of an inch 
in diameter. Now heat the loop in the blowpipe flame 
and dip into the dry borax, soda or 8. Ph., as the case 
may be, the adhering material fused, and again 
dipping into the reagent and fused until a clear bead is 
formed within the loop. Now fuse the bead again, and 
this time dip it into the finely powdered mineral ; fuse 
this and dip again, noting each time the colors which 
the bead assumes, both when hot and cold. Care should 
be taken not to take too much of the mineral at a time, 
it being better to add it to the bead in minute quanti- 
ties until the desired depth of color is obtained. In se- 
lecting the mineral to be tested, care should be taken 
to not confound two or more minerals together as this 7 
often causes unnecessary conflicts in tests. 
(e€) TESTS ON CHARCOAL. 
s 
Mix the pulverized mineral and _ reagent 
(slightly moistened) together in a little round 
