of rendering Plallna malleable. 3 



prevent the particles from cohering in the further stages of the 

 process. Since the whole will require to be well washed in 

 clean water, the operator, in the later stages of grinding, will 

 find his work much facilitated by the addition of water, in or- 

 der to remove the finer portions, as soon as they are suffi- 

 ciently 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 consequently cannot be freed like other me- 

 tals, from its impurities, during igneous fusion, by fluxes, nor 

 be rendered homogeneous by liquefaction, the mechanical dif- 

 fusion through water should here be made to answer, as far 

 as may be, the purposes of melting; in allowing earthy mat- 

 ters to come to tlie 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 platuia may be obtained as pure * 

 as other metals are rendered by the various processes of or- 

 dinary metallurgy ; and if now poui'ed over, and allowed to 

 subside in a clean basin, a uniform mud or pulp will be ob- 

 tained, ready for the further process of casting. 



The mould which I have used for casting, is a brass barrel, 

 G^ inches long, turned rather taper within, with a view to fa- 

 cilitate 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 witli 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 tjuite full with the mud of platina ; 

 which, subsiding to the bottom of the water, is sure to fill the 



been burnished with any liard substance, the welding will be eflected, if at 

 all, witli very izrcat difliciilty. 



When the powder of platina h^^ been over-heated in decomposing the 

 amnionio-inniiate, 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 

 i.al ainuioniac in nitric acid. 



• Sulphuric acid, digested upon the gray powder of platina, thus purified, 

 extracted Icbi than 1-lOOOdth [lart of iron. 



\\ 2 barrel 



