Organic Bodies containing Metals. 161 



being employed ; the sealed tubes containing these ingredients 

 should be placed near the focus of a large parabolic reflector, 

 the temperature being prevented,, if necessary, from rising too 

 high by immersing them in water or in a solution of sulphate of 

 copper. The unconcentrated rays of the sun, or even diffused 

 daylight, are quite sufficient to determine the formation of the 

 crystalline body; but an exposure of several vreeks, or even 

 months, would be necessary for the completion of the change, 

 which is effected by the use of the reflector in a few days of 

 bright sunshine. The liquid gradually assumes a straw-yellow 

 colour, but its solidification is prevented as long as possible at 

 the end of the operation, by allowing the temperature to rise 20° 

 or 30° C. above that of the atmosphere; thus nearly the whole 

 of the iodide of sethyle becomes united with tin. When heat 

 instead of light is employed to effect the combination, the tubes 

 should not be more than half an inch in diameter ; and to avoid 

 the risk of explosion, should not be more than one-fourth filled 

 with the materials : the combination takes place at about 180° C. 

 The agency of heat is therefore much less convenient than that 

 of light in the production of this reaction, which is also never so 

 complete as when the latter agent is employed ; I have satisfied 

 myself, however, that the results are the same in both cases. 



Examination of solid products. — The capillary extremities of 

 the tubes in which the iodide of sethyle had been exposed to the 

 action of tin, were broken off under sulphuretted water and 

 beneath a jar filled with the same liquid*; the gases evolved 

 were preserved for eudiometrical investigation. The crystalline 

 product of the reaction was then withdrawn from the tubes, and 

 after being exposed to a gentle heat for a few minutes to expel 

 the iodide of sethyle that had escaped combination, was treated 

 with alcohol, in which the crystals readily dissolved, leaving only 

 a small residue of a bright red colour, which proved to be proto- 

 iodide of tin. The filtered alcoholic solution was then placed 

 over sulphuric acid in vacuo, where it soon deposited a large 

 crop of long needle-like crystals, which, when freed from the 

 mother-liquor, washed with a small quantity of dilute alcohol, 

 dried between folds of bibulous paper, and finally over sulphuric 

 acid in vacuo, yielded the following analytical results : — 



I. 1'6806 grm., treated with aqueous solution of ammonia, 

 was immediately decomposed, iodide of ammonium being formed, 

 whilst the iodine in the original compound became, as I shall 

 show below, replaced by oxygen ; this oxide, which is almost 

 absolutely insoluble in ammonia, collected on a filter and dried 

 at 100° C., weighed '7263 grm.; decomposed by boiling nitric 

 acid it gave -5811 grm. peroxide of tin. The ammoniacal solu- 

 * Journal of Chemical Society, vol. ii. p. 267. 



