APPLICATION OF PLATINUM UPON OTHER METALS. 113 
and express all the air lodged between the two plates. The 
pressure, to effect this, should be very great, and the prelimi- 
nary experiments with a roller not producing the desired 
effect, attempts were made with a hydraulic press at a pres- 
sure of about thirty atmospheres. The first attempt was 
made about two years since, upon a plate of two inches; and 
since, the experiment has been repeated many times upon 
plates of three and four inches square, and on plates of five 
and six inches in length. 
To prevent costly and useless attempts in those who desire 
to repeat these experiments, the following details are given: 
A very pure piece of platinum in the form of a square and 
thin plate is to be taken, together with a plate of copper some- 
what larger and much thicker. The pieces are to be tho- 
roughly polished, more especially on the sides which are to 
be in contact; they are then to be placed the one on the other, 
and being pressed close together, they are to be enveloped in 
a thin band of copper wound around in a spiral, (this precau- 
tion is indispensable to prevent the oxidation of the copper on 
its interior surface.) This being complete, they are to be ra- 
pidly heated in a forge previously in operation, and when a 
red heat is attained, they are taken out, placed under the pis- 
ton of the press, and rapidly compressed while yet red. On 
being released from the piston, the two pieces will be found 
united, the plating with platinum being completed in a very 
short time, but a few minutes sufficing for the experiment 
when every thing is prepared. 
The experiments by compression give very good results; 
the adhesion between the two plates takes place over the 
whole surface; the two pieces are perfectly united together, 
and by passing them between rollers we can obtain very 
thin plates. 
By this first process, we may obtain vessels of great thin- 
ness as to the platinum, while at the same time protection is 
afforded by another metal with which it is connected. The 
proportion of the metals in the experiments made, was as one 
to thirty, and the platinum on each square inch weighed only 
VOL. V. — NO. II. 15 
