1815.] in the Physical Sciences. 21 



cliemical purposes. Its specific gravity is in general not so high as 

 our London platinum, though 1 once had a cruciiile made in Paris 

 above il in specific gravity. M. Leithner, who has the charge of 

 the porcelain manufactory at Vienna, has lately proposed a new 

 method of rendering platinum malleable. It is exceedingly simple, 

 atid appears to answer well enough in a small scale, though it is not 

 adapted for the construction of large vessels. It consists in making 

 up the fine powder of pure platinum into a paste with oil of tur- 

 pentine, and laying it in coats upon ])aper, allowing one coat to dry 

 before another is applied, and continuing to add coats till the layer 

 of platinum is of sufficient thickness. V\ hen this is done upon 

 porcelain, and the vessel afterwards exposed to the temperature of 

 from 14° to 18° Wedgwood, the platinum adheres, and may be 

 burnished. When laid upon paper, and then exposed to a strong 

 heat gradually raised, a sheet of platinum remains, which may be 

 hammered, and converted into any shape that is wanted. 



7. Palladium and Rhodium. — Vauquelin's method of separating 

 these metals from crude platina, and obtaining them in a state of 

 puritVj has been given so lately in the Annals of Philosophy, that I 

 do not think it necessary to repeat it here, it is sufficiently comj)li- 

 cated ; and, as far at least as palladium is concerned, does not 

 seem nearly so easy as the method previously given by Dr. Wol- 

 laston by means of prussiate of mercury, though it is possible that 

 Vauquelin's process may yield a greater quantity. 



8. Gilding on Sled. — Gehlen has tried the following method of 

 gilding on steel, and found it to answer. The steel is to be in the 

 first place polished ; the part to be gilt is to be rendered rough by 

 means of nitric acid ; the steel is then to be dipped into the solution 

 containing the gold ; the gold adheres to the rough part of the 

 steel, and may be burnished. 



y. Phosphuret of' Copper. — If we believe Bobereiner, phosphuret 

 of copper, prepared by Sage's method, contains not only copper 

 and phosphorus, but likewise calcium, lo this last metal, in his 

 opinion, the analogy of the phosphuret to steel is owing. 



10. Separation of Gold and Silver. — Professor Schnaubert, of 

 Moscow, has lately made several attempts to separate silver from 

 gold by boiling the alloy in sulphuric acid ; this acid dissolves the 

 silver, and leaves the gold, 'i'he process, though Ijy no means 

 brought to a state of perfection, promises at present to be attended 

 with success. The great difference between the price of sulphuric 

 acid and nitric acid, which is usually employed for the purpose. 

 Tenders it desirable that this process, which 1 conceive originated 

 with Mr. Kcir, should be subjected to farther trials. 



1 1. Zmr. — From my analysis of blende, published in the Annals 

 of Philosophy, iv. 8!), we may conclude that oxide of /inc is com- 

 jiosed of 100 metal + 'I'i'^'l oxygen; and sulpliuret of zinc of 

 100 metal + 48-81 sulphur; and an atom of /iiic weighs l-OyS. 



12. Antimony. — From my analysis of sul|)lunct of antimony, 

 (Ibid. p. y5,) it foHows that it is composed of 100 metal + ;{5-55(> 



