216 THE USE OF IODINE IN BLOWPIPING. 
above the copious plumbic iodide. This is a test re- 
quiring much skill and good judgment. 
These are the only tests employing iodine in blow- 
piping that I can find published prior to 1883, and I want 
to call your attention to two salient features in them. 
Bunsen’s films demanded a white surface rapidly 
chilled. 
Von Kobell’s films demanded a support that should 
withstand the heat of the blowpipe flame. 
The next step was published in 1883 by Dr. E. Haanel, 
Professor of chemistry in Victoria college, Coburg, 
Province of Ontario, in the Transactions of the Royal 
Society of Canada. Hewas led, he says in his paper, to 
remove the difficulty experienced by students in dis- 
_tinguishing the oxide coatings of bismuth on charcoal 
from the similar one of lead by converting both these 
coatings intoiodides. The method was to drop hydriodic 
acid on the coating in question and then direct the flame 
upon the charcoal just in front of the moistened spot. 
The heat of the flame volatilized the respective iodides. 
which were again deposited on the charcoal at a greater 
distance, and assumed. characteristic colors: bismuth, 
brown ; lead, canary yellow. This was an improvement 
on Von Kobell’s method since a suspected film could 
readily be differentiated. The drawback was the use of 
the unstable hydriodic acid. 
In extending his observations, he soon came to find 
that charcoal was not a satisfactory support on which to 
utilize to the fullest extent the peculiar reactions of 
hydriodic acid, so he set out to find a substitute. It must 
be cheap and readily made. Its surface must be smooth 
and white, uninfluenced by the flame and readily chilled. 
The first two are Bunsen’s conditions ; the last two are 
Von Kobell’s. Dr. Haanel’s additional requirement was 
that it should absorb hydriodic acid. After much ex- 
perimentation he produced tablets made of plaster of 
100 
