Intelligence and Miscellaneous Articles. 385 



M. Lassaigne observes that this iodide contains exactly half as 

 much iodine as that which he first prepared in 1829 by treating 

 perchloride of platina with iodide of potassium. {Journal de Chimie 

 Medicate.) That iodide, of course consisted of 



One atom of iodine . . 126 



Two atoms of platina 192 



318. 



Action of Iodide of Potassium upon Protiodide of Platina. — Dis- 

 solve iodide of potassium in six parts of water, and put some prot- 

 iodide of platina into the solution ; suffer them to remain at the tem- 

 perature of the air, with occasional stirring, for twenty-four hours : 

 the solution becomes of a light orange colour, and the greater part 

 of the iodide remains undissolved. When heated in a water bath 

 nearly to ebullition, for several hours, the solution becomes of a 

 deeper colour, but the greater part of the iodide of platina remains 

 undissolved. There appears to be formed a double iodide of potas- 

 sium and platina, which crystallizes, by slow evaporation, in rect- 

 angular tables of a lemon-yellow colour. As it is impossible to 

 separate this salt from a portion of free iodide of potassium, it has 

 not been analysed. 



Hydriodic Acid and Protiodide of Platina. — Hydriodic acid of 

 sp. gr. 1*038, when mixed with protiodide of platina at common 

 temperatures, gradually decomposes and converts it into bi-iodide, 

 which dissolves in the acid and produces a red compound, and 

 metallic platina, which appears on the surface of the liquid, in the 

 state of a steel-gray pellicle. 



Bi-iodide of Platina is very easily prepared, by adding a solution 

 of iodide of potassium to one of bichloride of platina diluted with 

 water. At the moment these liquors are mixed, an orange red co- 

 lour is produced, which soon becomes deeper and of a wine red-colour, 

 without the formation of any precipitate ; but if the mixture be 

 heated it becomes brown, turbid, and when boiling deposits a flaky or 

 crystalline black powder, according to the strength of the solutions. 

 During precipitation vapour of iodine is given out, owing to the 

 decomposition of a portion of iodide of potassium by an excess of 

 acid, which remains mixed with the bichloride of platina ; when this 

 excess of acid is avoided as much as possible, no vapour of iodine 

 is evolved. The bi-iodide of platina, after washing with boiling 

 water, may be dried over sulphuric acid or by a water bath. 



This iodide, like the protiodide, is a black powder, similar to pow- 

 dered charcoal, and stains the fingers like it ; sometimes it has a cry- 

 stalline appearance, resembling powdered peroxide of manganese. It 

 is inodorous, insipid, unacted upon by water, suffering no decom- 

 position even when boiled in it. It is more easily decomposed by 

 heat than the protiodide, giving out iodine at 268° Fahr. - It is solu- 

 ble in cold alcohol, but more so in hot; the solution is of a greenish 

 yellow colour: it is not decomposed by water, and by evaporation to 

 dryness it leaves a brownish residue, which is insoluble in water 

 and has the properties of protiodide of platina. When iodine is 



Third Scries. Vol. 3. No. 17. Nov. 1833. 3 D 



