264 ON COATING GLASS VESSELS WITH COPPER. 
ART. LVIIL— ON COATING GLASS VESSELS WITH COPPER. 
By J. B. Edwards, F. C. S. 
Late Chemical Assistant in the Pharmaceutical Laboratory. 
While assisting Mr. Redwood last session, I had occa- 
sion to make some experiments for him on this subject, with 
a view to obtain the necessary data for the best process. 
We then succeeded in coating vessels with copper, but did 
not obtain that smooth, equable surface and even texture 
peculiar to the specimens brought from Paris. 
I have lately resumed these experiments, and succeeded 
in obtaining many specimens equal in every respect to the 
French ones both in smoothness and texture. 
I first tried to deposite the metal from the cyanide of 
copper and potassium, and with success, for that salt 
deposites it in a state of great smoothness and beauty. I 
found, however, several objections to this mode — it was 
troublesome, on account of requiring an elevated tempera- 
ture (from 100° to 130°.) The solution did not keep of 
uniform strength, as it soon became surcharged with copper 
which checked the operation, and though of great beauty 
when just finished, the coating soon changed color, assuming 
a blackened appearance. I therefore again tried the sul- 
phate, and found no difficulty occurring with that salt, if 
the following points are carefully attended to : — 
1st. The bronze-powder must be of the best quality and 
finely divided — the varnish should be nearly dry before 
being covered with it, and after the bronze is on should be 
allowed to become perfectly hard and dry before it is im- 
mersed in the solution. 
2d. The battery power should be regulated by the size 
of the vessel to be covered. A few experiments will point 
out the proper size. 
3d. The solution (that recommended in Practical Phar- 
macy, page 320, answers perfectly,) should be kept as 
