364 On some Comlinations ofPIathia. 



obliged me to relinquish this design. I shall, however, state 

 a few facts I have observed relative to these compounds. 



The potash muriate of plalina, when properly prepared, 

 Biakcs, I presume, a good colour for painters. I am not 

 aware that this substance has been proposed as a pigment, 

 or that the fact is generally known ; I shall therefore de- 

 scribe the method 1 have adopted to procure it, together 

 with the properties which seem to characterize and fit it for 

 this purpose. 



The purified platina of commerce should be dissolved ia 

 nitro-muriatic acid, composed of about three parts of muria- 

 tic and one part of nitrous acid, the solution evaporated 

 nearly to dryness, redissolved in water, filtered and treated 

 with a strong solution of nitrate or muriate of potash, till no 

 further precipitate takes place. The precipitate should be 

 washed with a little distilled water, and dried at a mode- 

 rate heat. As the purified platina of commerce sometimes 

 contains other foreign metals, it is a necessary precaution, 

 first, to treat a little of the acid solution with a few drops 

 of muriate of ammonia. If the precipitate be of a bright 

 yellow colour, the platina is sufficiently pure for the pur- 

 pose; if, on the contrary, it be of a reddish or muddy 

 yellow, it should all be precipitated by muriate of ammonia, 

 ihe metal reduced at a red heat in a platina crucible, again 

 redissolved, and treated as at first proposed. 



This substance is of a fine yellow colour. It is not ap- 

 parently affected by the atmosphere. It mixes with the 

 oils without undergoing any sensible change. It is insolu- 

 ble in the mineral acids at the common temperature. It is 

 not acted on by a strong solution of caustic potash, soda or 

 ammonia. When well dried, it scarcely contams more 

 than 1 per cent, of water. When heated to a dull red in 

 close vessels, it undergoes little permanent change^ At a 

 strong red heat it affords chlorine gas, and an olive sub- 

 stance which I conceive is a peculiar compound which has 

 not been examined. The soda muriate of platina, when 

 dried and heated, furnishes analogous results. The olive 

 compounds obtained in these instances consist, I presume, 

 of chlorine, platina, and the alkali. 



From Bergman's experiments, Dr. Thomson'* states the 

 existence of triple sulphates and nitrates of platina. The 

 guiphate of plalina was unknown to ibis celebrated chemist, 

 and the nitrate is still unknown. These compounds, from the 

 experimcius I have made, appear to be merely the alkaline 

 muriates of platina. 



* System of Chemistry, vol. iiJ.p.l35. 



Platina 



