258 Chloriodide of Platinum. 



precipitate, and the solution is finally left colorless. This change Is 

 owing to the precipitation of the biiodide of platinum, while the hy- 

 driodate of potassa remains in solution. 



M. Lassaigne may have observed this fact, as the principle is in- 

 volved in the formation of the biiodide of platinum by his process, 

 but he does not mention it. 



Some of the iodoplatinate of potassium weighing 2.26 grains, was 

 put into a small dry quill-glass tube, hermetically sealed at one end, 

 and drawn down to a small beak at the other. The tube was heated 

 to redness, and iodine vapors escaped in abundance. The loss of 

 weight was 1.110 grains. 



Adopting Thomson's and Berzelius' numibers for iodine, platinum, 

 and potassium, upon the supposition that the compound is analogous 

 in composition to the ammonia muriate of platinum, the loss would 

 have been for Thomson's numbers, 1.08 grains, and for Berzelius' 

 numbers, 1.109 grains. From the near approximation of the loss 

 observed to the hypothetical composition, by the numbers of both 

 Thomson and Berzelius, and particularly the latter, there is no doubt 

 but it is composed of biiodide of platinum, 1 atom — iodide of potas- 

 sium, 1 atom, or by 



Thomson's numbers. By Berzelius* numbers. 

 Biiodide of platinum, 67.71 _ _ _ - - 67.86 

 Iodide of potassium, 32.29 32.14 



100.00 100.00 



VII. Chloriodide of Platinum. 



This compound and the preceding, were observed by me in tl:\e 

 winter of 1830. The iodoplatinate of potassium, had been observed 

 by several persons ; bvit not examined. Several years since Profs. 

 Silliman, Torrey, Berzelius and others had observed the red color 

 on adding hydriodate of potassa to muriate of platinum. 



The chloriodide of platinum, is easily formed by adding an excess 

 of hydriodic acid to muriate of platinum, evaporating to dryness, and 

 heating the dry mass to about 300° F. The excess of hydriodic acid 

 with some chloride of iodine, pass over into the receiver, while the 

 chloriodide of platinum remains. It is a black powder, stains the 

 fingers, is insoluble in water, slightly soluble in alchohol, soluble in 

 potassa giving a red solution from which it is precipitated unchanged 

 by sulphuric acid. At a temperature between 400° and 600° F. 

 it is decomposed, brownish yellow vapor of chloride of iodine, and 



