BOILING OF LIQUIDS IN GLASS VESSELS. 333 
apparatus which I have found convenient for effecting the 
distillation of small quantities of balsam of copaiba. 
I Having observed that liquids, which are subject to bump- 
ing when boiled in vessels of glass, present no such effect if 
the process be conducted in those made of metal, I thought 
it probable that by coating the inner surface of the glass 
with silver, in the manner adopted by Mr. Drayton, the 
irregularity of ebullition alluded to would be prevented. 
This I have found to be the case, and I have repeatedly 
used glass flasks coated on the inside with silver, for the 
distillation of balsam of copaiba, without experiencing in- 
convenience from the bumping of the liquid. The method 
I have adopted for preparing the flasks has been to throw 
down the silver by Drayton's process, so as to cover the 
lower part of the vessel, while the upper parts are left un- 
silvered. This is effected by introducing as much of the 
ammoniacal solution of silver as will cover the part to be 
coated. After the siker has been deposited by the addition 
of the essential oils, it is necessary to clean the flask from 
adhering oil by means of rectified spirit, several successive 
quantities of which should be boiled in it until the silver 
becomes perfectly clean and bright, and no smell of the oil 
remains. When the process has been successfully per- 
formed, and every trace of oil removed, the coating of silver 
may be rendered thicker by depositing a fresh portion of 
metal, from a solution of oxide of silver in cyanide of po- 
tassium, by electricity. 
Glass vessels may also be covered with platinum, by 
putting into them a solution of the chloride of that metal, 
adding thereto some formic acid, and then boiling the mix- 
ture. The coating of metallic platinum thus obtained, will 
not, generally, be so perfect and uniform as that of the 
silver deposited by the preceding process; but I h^ave fre- 
quently succeeded in getting a deposit of perfectly bright 
platinum in this way, which has adhered very strongly to 
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