ON OXIDE OF ZiriC. 
361 
izing action in the interior. This is an ingenious plan of regu- 
lating this kind of cold vulcanization. 
Another process which appears preferable on account of the 
salubrity and regularity of the operation, is due to the same in- 
ventor ; it consists of immersing in a closed vessel for three hours 
the objects to be vulcanized, in a solution of polysulphuret of po- 
tassium indicating 25° Beaume, at a temperature of 284°, and 
then washing in an alkaline solution, and afterwards in pure water. 
In this manner the useful amount of sulphur is combined with the 
caoutchouc without an excess being left in its pores ; and we thus 
avoid the inconveniences which result from the unequal sulphuriza- 
tion of the organic substance. — London Chem. Gaz. ,May 15, 1852. 
from Comptes Rendus> March 29, 1852. 
ON OXIDE OF ZINC. 
By Dr. Wittstein. 
Mohr (Archiv der Pharmacie, lxv., 137) has found that a full 
red heat is not essential for the complete separation of carbonic 
acid and water from the carbonate of zinc, but that a temperature 
of from 280° to 300° C. (= 536° to 572° Fahr.) suffices for 
their speedy and perfect expulsion. The operation can be per- 
formed in an uncoated glass alembic or porcelain dish. The 
preparation undergoes no change of color thereby (i. e., it re- 
mains perfectly white, whereas, the over-heated oxide shows a 
trace of yellow.) We now observe that it has become very mobile, 
and no longer adheres to the capsule, but floats on a layer of car- 
bonic acid and aqueous vapor. 
If a glass flask be used, it must be half filled with finely pulver- 
ized* carbonate of zinc, and placed on a triangle not too near a 
gentle coal fire. As soon as condensation of watery vapor takes 
place in the neck of the flask, this is to be stopped with a piece 
of cloth, and gently shaken in a circular direction. Thereby those 
parts at the lower surface of the flask are mixed with the rest of 
* This condition is essential to the success of the operation. 
