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Proceedings of the Royal Society 
reaction. Although the liquid, after addition of the cyanide, is 
markedly alkaline, nevertheless the presence of free acid in the 
bismuth solution is necessary ; that this acid need not be nitric acid 
was shown by adding potassium cyanide to solution of bismuthous 
oxide in slight excess of hydrochloric and sulphuric acids respect- 
ively; in each case the puce-red salt was obtained on boiling. 
It is, I think, evident, that to ensure production of the new 
salt, rapid chemical change — partly oxidation, partly formation of 
bismuth cyanide — must occur; neither bismuthous oxide nor any 
other salt must be allowed to get permanently produced, the whole 
system must not settle down into stable equilibrium until it is 
forced to assume that configuration of which the complex oxy- 
cyanide is a component part. 
5. Bismuth Oxycyanide — probably 2Bi(dST) 5 .5Bi 2 0 5 — when dried 
at 140°-150° is a reddish-brown solid, somewhat similar in 
appearance to lead dioxide, but showing a more decided puce 
colour than that salt. It begins to undergo change at about 200°, 
but the loss of weight at that temperature is small ; about half a 
gram of the salt lost 3*50 per cent, at 210°, and 7 -50 per cent, at 
350° (the oxycyanide in changing to Bi 2 Q 3 loses about 12 per cent.). 
When a large quantity of the salt is heated in a crucible, a consider- 
able amount of metallic bismuth is produced ; but when quantities of 
from 0 *5 to 1 *0 grams are so heated the residue consists only of 
bismuthous oxide. 
The oxycyanide scarcely takes up water when exposed to ordinary 
or to moist air ; thus about half a gram increased only 1’80 per cent, 
in weight after 144 hours’ exposure over water. It does not suffer 
change when covered with water and exposed to< the action of 
sunshine. 
Bismuth oxycyanide is dissolved by hot concentrated nitric or 
sulphuric acid, with production of dark-red liquids, from which 
water causes precipitation of red substances containing bismuth, 
and soluble in hot potash solution. Hydrochloric acid dissolves the 
oxycyanide more slowly, a portion remaining undissolved even after 
continued action. When heated with a slight excess of potash 
these liquids yield reddish precipitates, which are mostly soluble in 
hot concentrated potash solution, and when any of these deep red 
acid solutions is boiled it is very slowly decomposed with ultimate 
