Procefs for rendering Plaiina malleable. 3 



A ftrong, hollowj inverted cone of crucible earth being 

 procured, with a correfponding ftopper to fit it, made of the 

 fame materials, the point of the latter is cut off about three- 

 fourths from the bafe. The platina, now in the ftate of a 

 hght yellow powder, is prefled tight into the cone, and, a 

 cover being fixed (lightly on, it is placed in an air-furnace*, 

 and the fire raifed gradually to a ftrong white heat. In the 

 mean time the conical ftopper, fixed in a pair of iron tongs 

 fuitable for the purpofe, is brought to a red, or to a bright 

 red heat. The cover being then removed from the cone, the 

 tongs with the heated ftopper is introduced through a hole 

 in the cover of the furnace, and preffed at firft gently on the 

 platina, at this time in a ftate nearly as foft as dough, till it 

 at length acquires a more folid confiftence. It is then re- 

 peatedly ftruck with the ftopper, as hard as the nature of the 

 materials will admit, till it appears to receive no farther im- 

 preflicn* The cone is then removed from the furnace, and- 

 being fiTr'^ lightly with a hammer, the platina falls out in 

 a meta!!ic Iratton, from which ftate it may be drawn, by re- 

 peatedly heating and gently hammering, into a bar fit for 

 flatting, drawing into wire, planifliing, &c. 



Befides the comparative facility of this procefs, it has the 

 farther advantage of rendering the platina much purer than 

 when red-hot iron is obliged to be had recourfe to ; for pla- 

 tina, when of a white heat, has a ftrong affinity ^or iron, and, 

 with whatever care it may have been previoufly feparated 

 from that metal, will be found to have taken up a portion of 

 it, when it is employed, of a red heat, to ferve to unite the 

 particles of the platina. To the fupcrior purity of platina, 

 rendered malleable by the procefs before defcribed, I attri- 

 bute the greater fpecific gravity which I find it to poflefs, 

 than that prepared by other methods. Having taken the 

 fpecific gravity of about ten penny weights of it, which I 

 had previoufly pafTed repeatedly through a flatting mill, I 

 found it to be 22*26. 



Fofter Lane, January 3, 1800. 



• The one I employ is portable, and tho chamber for the fire only 

 eight inches in diameter. K, 



B» II. Reflect 



