M. Kuhlmann on the Extraction of Thallium. 211 



When the dry protoxide is heated with absolute alcohol it is 

 dissolved, and a thallic alcohol formed analogous to potassic 

 alcohol. It is a limpid oil of the specific gravity 3*50, and 

 scarcely less refrangible than bisulphide of carbon. It is little 

 soluble in alcohol, and is decomposed by water, forming pure 

 protoxide of thallium. 



When thallium is completely burned in oxygen, it forms an 

 insoluble black oxide of the composition ThO 3 . This melts at a 

 red heat and disengages oxygen. It forms salts with hydro- 

 chloric, sulphuric, and nitric acids, which are not very stable. 



When sesquichloride of thallium is treated with potash, a 

 brown oxide is precipitated, and protochloride of thallium remains 

 in solution. This oxide unites with acids more readily than the 

 black oxide, from which it differs by containing an equivalent of 

 water. 



The carbonate of thallium, ThO CO 2 , dissolves to the extent of 

 about 5 per cent, in water at the ordinary temperature, and to 

 about 22 in water at 100° C. It crystallizes in long, flattened, 

 prismatic needles, readily fusible to a grey mass whose density 

 is 7-06. 



The sulphate, ThO SO 3 , crystallizes in beautiful oblique rhombic 

 prisms, somewhat less soluble than the carbonate. 



The nitrate, ThO NO 5 , is the most soluble of the salts of thal- 

 lium. 100 grms. of water at 18° dissolve 9'75 grms., and 580 

 grms. at a temperature of 107°. 



Thallium appears to form three chlorides. The most stable is 

 the protochloride, ThCl, which has great analogy with chloride of 

 silver, except in the matter of solubility. The sesquichloride of 

 thallium, Th 2 CI 3 , forms beautiful yellow hexagonal plates, soluble 

 without decomposition in acidulated water to the extent of about 

 5 per cent. It melts at 400° to a brown volatile liquid, and 

 solidifies to a yellowish-brown mass, the density of which is 5*90. 



Both these chlorides appear capable of absorbing 1 to 1*5 

 equivalent of chlorine to form unstable perchlorides > which heat 

 alone decomposes. 



Although the metal thallium has, by means of the spectro- 

 scope, been found to exist in several specimens of pyrites from 

 different sources, yet Bottger, who had tried to detect its 

 presence in a great many samples of the deposits in sulphuric 

 acid works in which pyrites is burned, was not able to do so; 

 Kuhlmann, in the deposits from whose works Lamy extracted 

 thallium, describes* their exceptional construction, which per- 

 mitted the accumulation of large quantities of this substance. 



* Cornptes Rendus, January 26, 1863. 

 P2 



