PREPARATION OF OXIDE OP ZING, 
171 
ratory, and found that it was very deficient in the power of 
covering, which is dependent upon the opacity of the 
paint. 
Mr. Midgley said he had seen it used, and thought 
that although it did not cover so well as white lead, yet, 
taking this deficiency into account, the price at which it 
could be made would compensate for the defect. He had 
calculated that three coats of zinc paint would be equiva- 
lent to two coats of lead paint. 
Mr. Hooper remarked that oxide of zinc paint was at 
present sold in London, and he believed the oxide of zinc 
used in making it was imported from abroad. This, at 
least, he knew to be the case with the paint prepared at 
one manufactory. 
Mr. Scaklan had been engaged some years ago in some 
experiments on the preparation of oxide of zinc by combus- 
tion ; his object having been to effect the oxidation by 
causing a current of hot air to pass over the surface of 
melted zinc. The results, however, had not realized his 
anticipations. 
Mr. Bell had tried, in the preparation of zinc ointment, 
some of the oxide of zinc made by combustion as a substi- 
tute for that made in the usual way by precipitation and 
calcination, but found that in the state in which he had re- 
ceived it, it was not sufficiently smooth and impalpable. It 
required to be treated by elutriation before being used, so 
as to remove any minute particles of metal that might re- 
main mixed with it. 
Mr. Redwood thought that some benefit would result from 
the discussion of this subject, by its affording an opportu- 
nity for again directing the attention of the retail Pharma- 
ceutist to the impurity of much of the oxide of zinc of com- 
merce. He (Mr. R.) had read a paper before the Society 
some years ago on this subject, the object of which was to 
show that nearly all of what was met with in commerce, and 
used in medicine as oxide of zinc was either carbonate of 
