iMR. HENRY ON THE COMPOUNDS OF TIN AND IODINE. 365 



tiful acicular crystals, which, after being washed with a little water, lost their lustre 

 by drying at a very gentle heat. 



50 parts gave 20*7 parts peroxide =32"36 per cent, tin ; 10 grs. of tliis were heated 

 in a small tube, tightly corked, at first gently, and afterwards to complete fusion ; a 

 little water condensed on the upper part of the tube with a minute portion of binio- 

 dide. When cold the tube was cut, the fused mass removed, and found to have lost 

 \'o gr. ; it was slightly oxidized on the surface, and perfectly resembled the protiodide 

 procured in the former experiments. 



25 '3 grs. of the same salt were heated to from 380° to 400° in an open porcelain 

 crucible, a sublimate was produced, which was received in a paper cone, so placed 

 on the crucible as not to prevent the access of air ; when no more vapour was given 

 off, the crucible was cooled and weighed ; the residue was found to weigh 6 04 grs. ; 

 it was ignited, and then weighed 5*91 grs., and was peroxide of tin. The sublimate, 

 which was in small brilliant orange-red crystals, was biniodide of tin ; for 460 grs., 

 decomposed with nitric acid and ignited, gave 1*115 peroxide = 1 906 per cent, of metal. 



Now, supposing that two atoms of protiodide of tin had been decomposed, giving 

 rise to one atom of periodide, and cme atom of peroxide of tin, 25*3 grs. of protiodide 

 should have left 5*13 grs. of peroxide, which is sufficiently near the quantity obtained 

 to determine the nature of the decomposition. Berzelius states that the proto- 

 fluoride of tin is converted, by the action of the atmosphere, into SnF^, SnO^ ; a 

 decomposition exactly analogous to that above described. 



I have not succeeded in obtaining a combination of tin and iodine corresponding 

 to the sesquioxide, although Boullay conjectured that some yellow crystals, which 

 he obtained on adding to a solution of protochloride of tin a solution of iodide of 

 potassium, in which an additional half-atom was dissolved, were sesqui-iodide ; the 

 crystals I obtained by this method were found to be pure protiodide. 



On adding iodine to a solution of protochloride of tin, this salt suffers a remarkable 

 decomposition ; if its solution be concentrated, an iodide of tin is precipitated, and a 

 combination of chloride and iodide of the metal, in definite proportions, remains dis- 

 solved in the solution. If the iodine be added in excess, so that the solution acquires 

 a brown colour, it yields crystals of biniodide on evaporation ; if, on the other hand, 

 the protochloride be in excess, a portion of the protiodide is precipitated, and the re- 

 mainder unites with protochloride of tin, in the proportion of one equivalent of each 

 substance, and it remains dissolved in the solution of protochloride, but may be sepa- 

 rated by evaporation in the form of delicate acicular crystals of a silky lustre, and 

 straw-yellow colour. 



On adding iodine to an equal weight of protochloride of tin, dissolved in a small 

 quantity of water, I obtained some minute red crystals, which yielded on analysis 



Per cent. 

 Iodine 79*30 



Tin ...... 19-98 



99-28 



