OF RENDERING PLATINA MALLEABLE. 
3 
operator, in the later stages of grinding, will find his work much facilitated by 
the addition of water, in order to remove the finer portions, as soon as they are 
sufficiently reduced to be suspended in it. 
Those who would view this subject scientifically should here consider, that 
as platina cannot be fused by the utmost heat of our furnaces, and conse- 
quently cannot be freed like other metals, from its impurities, during igneous 
fusion, by fluxes, nor be rendered homogeneous by liquefaction, the mechani- 
cal diffusion through water should here be made to answer, as far as may be, 
the purposes of melting ; in allowing earthy matters to come to the surface by 
their superior lightness, and in making the solvent powers of water effect, as 
far as possible, the purifying powers of borax and other fluxes in removing 
soluble oxides. 
By repeated washing, shaking, and decanting, the finer parts of the gray 
powder of platina may be obtained as pure* as other metals are rendered by 
the various processes of ordinary metallurgy; and if now poured over, and 
allowed to subside in a clean basin, a uniform mud or pulp will be obtained, 
ready for the further process of casting. 
The mould which I have used for casting, is a brass barrel, 6§ inches long, 
turned rather taper within, with a view to facilitate the extraction of the ingot 
to be formed, being 1.12 inches in diameter at top, and 1.23 inches at a quarter 
of an inch from the bottom, and plugged at its larger extremity with a stopper 
of steel, that enters the barrel to the depth of a quarter of an inch. The inside 
of the mould being now well greased with a little lard, and the stopper being 
fitted tight into the barrel by surrounding it with blotting-paper, (for the paper 
facilitates the extraction of the stopper, and allows the escape of water during 
compression,) the barrel is to be set upright in a jug of water, and is itself to 
be filled with that fluid. It is next to be filled quite full with the mud of pla- 
tina ; which, subsiding to the bottom of the water, is sure to fill the barrel 
become firmly welded together ; but if the surfaces have previously been burnished with any hard 
substance, the welding will be effected, if at all, with very great difficulty. 
When the powder of platina has been over-heated in decomposing the ammonio-muriate, or has been 
burnished in the grinding, I have in vain endeavoured to give it a welding surface, by steeping it in a 
solution of sal-ammoniac in nitric acid. 
* Sulphuric acid, digested upon the gray powder of platina, thus purified, extracted less than 
-ns V o-th part of iron. 
