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XVII. On the Compounds of Tin and Iodine. By Thomas H. Henry, Esq. 

 Communicated hy R. Phillips, Esq.^ F.R.S. 



Received March 31, — Read June 19, 1845. 



In a paper by Sii- H. Davy, published in the Philosophical Transactions, 1814, he 

 describes the compound of tin and iodine procured by heating these bodies together, 

 out of the contact of air, as of a deep orange colour, fusible at a moderate heat, and 

 volatile at a higher temperature. 



The compound obtained by Gay-Lussac, by gently heating tin with twice its weight 

 of iodine, and more recently by Rammelsberg, by the same method*, is described 

 by them as a reddish-brown, transparent substance, yielding a powder of a dirty 

 orange-yellow colour, and easily fusible. 



A compound of tin and iodine was procured by BouLLAY-f-, by precipitating a 

 solution of protochloride of tin with iodide of potassium, in slight excess. 



The combinations procured by these methods have been considered to be identical 

 in composition, although the compound procured both by Gay-Lussac and by Ram- 

 melsberg is stated by them to be decomposed by water, while the salt of Boullay 

 is described by him as soluble in water without decomposition. 



It will be seen, I think, from the following experiments, that the substance procured 

 by heating tin with twice its weight of iodine, is a mixture of two salts, differing in 

 composition, one of which is soluble in water to a slight extent, without suffering 

 decomposition, while the other is immediately decomposed on bringing it in contact 

 with water, the former being the real protiodide described by Boullay, and the latter 

 a biniodide, a salt which has not yet, to my knowledge at least, been described, but 

 which must have been the compound mentioned by Sir H. Davy, as it is of a brilliant 

 orange colour, and sublimes at a temperature of 356° Fahr., while the protiodide, I 

 find, may be heated to redness, out of the contact of air, without subliming. 



lOOgrs. of tin, in a state of minute division, were mixed with 220 grs. of iodine, 

 the mixture placed in a porcelain crucible well-covered, and sufficient heat being 

 applied to fuse the iodine, violent action immediately took place, accompanied by the 

 evolution of much heat and the sublimation of a portion of the iodine ; when the 

 action had ceased and the crucible had become cool, a brown transparent crystalline 

 mass, weighing 310 grs., was removed from it ; 10 grs. of iodine had been sublimed, 

 therefore, by the heat evolved during the combination ; upon breaking this mass, 

 however, a button of metallic tin, weighing 45 grs., was found inclosed in it. This 



* Gmelin, Handbuch, vol. iii. f Annales de Chimie, xxxiv. 372, 



