142 
NEW TEST FOR PRUSSIC ACID, ETC. 
The gutta percha is in thin films, varying in colour from 
a pale yellow to a pinkish tinge, and is destitute both of 
taste and smell. It is hard at* a common temperature, but 
when immersed in boiling water, it softens so much, as to 
be capable of being beaten into a mass, and formed into 
any shape required ; this, however, must be done imme- 
diately, for the mass on cooling becomes hard and un- 
yielding. 
When in a soft state, it can be stretched out into thin 
slips much beyond its usual length, but it does not recover 
its former bulk when the force is withdrawn. The slips 
are transparent and elastic. 
I feel no hesitation in pronouncing the guita percha a 
species of caoutchouc, possessing unquestionably some of 
its principal properties, but it is a species which I believe 
has not been examined before. — Pharm. Journ. from 
Journal of the Agricultural and Horticultural Society of 
India. 
ART. XLVJI. — ON A NEW TEST FOR PRUSSIC ACID, AND ON 
A SIMPLE METHOD OF PREPARING THE SULPHOC YANID E 
OF AMMONIUM. 
By Professor Liebig. 
When some sulphuret of ammonium and caustic ammo- 
nia are added to a concentrated aqueous solution of prussic 
acid, and the mixture heated with the addition of pure 
flowers of sulphur, the prussic acid is converted in a few 
minutes into sulphocyanide of ammonium. This metamor- 
phosis depends on the circumstance, that the higher sul- 
phurets of ammonium are instantly deprived by the cyanide 
