Chemical Science. 377 



stance in question. If the distillation be suspended from time 

 to time, and the retort allowed to cool, beautiful crystals of the 

 substance form in it. If strong alcohol be used in the above 

 operations, and but little water, then, upon adding water to the 

 filtered liquor, the substance is precipitated in abundance. 



This substance is solid, of a lemon yellow colour, tastes like 

 nitric ether, and has an odour like that of saffron. Its form is 

 a compressed hexahedron (esaedro schiacciato). It is insolu- 

 ble in water, alkalies, or acids, but soluble in alcohol and 

 ether. It fuses and sublimes by a gentle heat, but at a highef 

 temperature becomes discoloured, is decomposed, and evolves 

 vapours of iodine, leaving behind a mere trace of carbon. — 

 Giornule cli Fisica, v. 241. 



II Sig. Taddei has more lately resumed the examination of 

 this substance, particularly with regard to its composition. He 

 recognises in it the same body as that discovered by M. Serullas, 

 and which the latter chemist formed in various ways, as by the 

 action of potash on an alcoholic solution of iodine; by the action 

 of alloys of potassium and antimony on a similar solution i and 

 by passing water and iodine in vapour over hot charcoal. 



Taddei found the substance to act on mercury, copper, and 

 silver, forming iodides of these metals. When raised to a high 

 temperature it was decomposed, hence he endeavoured in this 

 way to ascertain the presence of hydrogen in it. No gas could, 

 however, be obtained from it, and the absence of hydrogen was 

 considered as established. The presence of carbon was ascer- 

 tained in the residuum after decomposition by its producing 

 carbonic acid when burnt in oxygen, and by its converting sul- 

 phate of barytes into sulphuret, which, on treatment with an 

 acid, gave sulphuretted hydrogen gas. 



The next object was to ascertain the quantities of the two 

 elements found in it. The iodine was estimated thus : a given 

 weight was decomposed by heat in a long tube cf glass, and the 

 iodine washed out by alcohol ; the solution was dilutedwith 

 water, and sulphuretted hydrogen gas passed through it; when 

 it was presumed that all the iodine had been converted into 

 hydroidic acid, the sulphur thrown down was collected, "weighed, 

 and the quantity of iodine inferred by the theory of proportional 

 quantities. The carbon was carefully collected, introduced into 

 a porcelain tube, to one end of which was attached a bladder 

 containing a portion of oxygen, whilst from the other a tube led 

 to a mercurial apparatus; the tube was then heated, the charcoal 

 burnt, and its quantity estimated from the quantity of carbonic 

 acid gas produced. Nearly the same experiment was repeated 

 on the original iodide of carbon, and the same quantity of car- 

 bonic acid gas obtained. 



The results of these experiments give the proportion of the 

 carbon to the iodine as 1 to 17 by weight, and M. Taddei 

 concludes, therefore, that the substance is a protiodide of carbon. 



