The New Metal Thallium. 



THE NEW METAL THALLIUM. 



On the 19th June Mr. Crookes read a paper on the new metal 

 thallium, before the Royal Society, and on the 25th of the same 

 month M. Lamy made a similar communication to the French 

 Academy. It is from these sources that we are able to lay 

 before our readers the following particulars : — In March 1861, 

 Mr. Crookes announced that a brilliant green line, exhibited by 

 some selenium residues, in the spectroscope method of analysis, 

 was an intimation of the existence of a new element. In the 

 following May he gave a further account of his discovery, 

 and named it thallium from our Greek OaXXos, on account of its 

 coloured line resembling the hue of vigorous vegetation. M. 

 Lamy, who was not aware of Mr. Crookes' s investigations, made 

 a subsequent but independent discovery of the same green ray, 

 which he noticed in the spectrum of a specimen of selenium 

 extracted by M. E. Kuhlmann from the refuse of chambers in 

 which sulphuric acid had been prepared by the combustion of 

 pyrites. Both chemists set to work to isolate the new metal ; 

 Mr. Crookes operating with crude sulphur distilled from Spanish 

 pyrites, and containing thallium to the extent of one or two 

 grains in the pound ; while M. Lamy used the selenium pre- 

 viously mentioned, from which he obtained salts of thallium that 

 gave up that metal by voltaic action. Mr. Crookes' s process 

 will be found in the Chemical News, July 5th. In substance 

 it consists in dissolving the metals out of crude sulphur or 

 pyrites by strong hydrochloric acid, to which nitric acid is 

 gradually added. The solution is evaporated to drive off the 

 nitric acid, and a little sulphuric added if required. It is neces- 

 sary to stop the evaporation before the solution becomes pasty. 

 It is then diluted, gently heated, filtered, rendered alkaline 

 with carbonate of soda, treated with an excess of cyanide of 

 potassium free from sulphide of potassium, heated once more, 

 and filtered again'. It is in the solution left after these pro- 

 cesses that the thallium remains, which is precipitated by sul- 

 phuretted hydrogen. If cadmium and mercury are present, 

 warm dilute sulphuric acid will remove the former, and the 

 sulphides of thallium and mercury are separable by dilute 

 nitric acid, which dissolves the first, and leaves the last. The 

 nitric acid solution is evaporated to dryness, the residue dis- 

 solved in hot sulphuric acid, and the thallium precipitated by a 

 piece of pure zinc. Thus obtained, the new metal looks first 

 like a deep brown powder, which soon changes to a heavy black 

 granular precipitate, to which fusion in hydrogen gives a co- 

 herent form. 



Thallium bears a strong physical resemblance to lead. Its 



