6 DR. WOLLASTON ON A METHOD 



straightened by blows upon the extremities, dexterously directed, so as to reduce 

 to a straight line the parts which project. 



The work of the operator is now so far complete, that the ingot of platina 

 may be reduced, by the processes of heating and forging, like that of any other 

 metal, to any form that may be required. After forging, the ingot is to be 

 cleaned from the ferruginous scales which its surface is apt to contract in the 

 fire, by smearing over its surface with a moistened mixture of equal parts by 

 measure of crystallized borax and common salt of tartar, which, ^vhen in fusion, 

 is a ready solvent of such impurities*, and then exposing it, upon a platina tray, 

 under an inverted pot, to the heat of a wind-furnace. The ingot on being taken 

 out of the furnace, is immediately to be plunged into dilute sulphuric acid, 

 which in the course of a few hours will entirely dissolve the flux adhering to the 

 surface. The ingot may then be flattened into leaf, drawn into wire, or sub- 

 mitted to any of the processes of which the most ductile metals are capable. 



The perfection of the methods above described, for giving to platina complete 

 malleability, will best be estimated by comparing the metal thus obtained, in 

 respect of its specific gravity, with platina which has undergone complete fusion ; 

 and by comparing it, in respect of its tenacity, with other metals possessing that 

 quality in the greatest perfection. 



The specific gravity of platina, drawn into fine wire, from a button which had 

 been completely fused by the late Dr. E. D. Clarke with an oxy-hydrogen 

 blowpipe, I found to be 21.16. The aggregate specific gravity of the cake of 

 metallic mud, when first introduced into the barrel, exclusively of moisture, is 

 about 4.3; when taken from the press, is about 10. That of the cake fully con- 

 tracted, on being taken out of the wind-furnace before forging, is from 17 to 

 17-7- The mean specific gravity of the platina, after forging, is about 21.25, 

 although that of some rods, after being drawn, is 2 1 .4 : but that of fine platina 



• The chemist will find this flux very serviceable for removing from his crucible or other vessels 

 of platina those ferruginous scales with which, after long use, and particularly after being strongly 

 heated in a coal or coke fire, they become incrusted. In the analysis of earthy minerals, I have been 

 in the habit of using a similar flux, composed of 2 parts by weight of crystallized carbonate of soda, 

 and 1 of crystallized borax, well ground together. It has the advantage of not acting, like caustic 

 alkali, upon the platina crucible, and is a powerful solvent of jargon and many other minerals, 

 which yield with difficulty to other fluxes. If the mineral to be operated on requires oxidation, in 

 order to decompose it, a little nitre or nitrate of soda may be added. 



