152 [June 19, 



attention towards procuring a source of thallium which would enable 

 me to prepare this body on the large scale ; my experiments having 

 hitherto been confined to mineralogical specimens which I had diffi- 

 culty in tracing to their source, and the whole amount of thallium 

 which I had as yet obtained not exceeding three grains in weight. 

 . After some delay, Mr. Thornthwaite was good enough to supply 

 me with a considerable quantity of crude sulphur distilled from 

 Spanish copper pyrites. In this I found thallium present to the 

 extent of one or two grains to the pound, and up to within the last 

 few months it has been from the element prepared from this source 

 that I have been working. I have recently, however, succeeded in 

 finding an ore containing thallium, which is worked in this country, 

 and from which I hope to be able to prepare the metal in larger 

 quantities. 



I have found the following the most advantageous method for 

 extracting the new element from sulphur or pyrites : 



Powder the ore very finely, and dissolve it as completely as possible 

 in strong hydrochloric acid, with gradual addition of nitric acid until 

 all solvent action ceases ; then dilute with water, and filter. Evapo- 

 rate down to drive off the excess of nitric acid, add a little sulphuric 

 acid if necessary, and take care that the solution does not get dry, 

 or even pasty. Then dilute with water, and heat gently, to be cer- 

 tain of getting all the soluble portion dissolved. Filter : if lead be 

 present, the greater portion will be left behind in this operation in 

 the form of insoluble sulphate. Dilute the. filtrate considerably, and 

 add a solution of carbonate of soda until the reaction is distinctly 

 alkaline ; then add an excess of solution of cyanide of potassium (free 

 from sulphide of potassium). Heat gently for some time, and then 

 filter. The precipitate contains the whole of the lead and bismuth 

 which may be present as carbonates, whilst the thallium is in solu- 

 tion. A current of sulphuretted hydrogen now being passed through 

 the liquid, precipitates all the thallium, whilst the copper, antimony, 

 tin, and arsenic remain dissolved. If cadmium and mercury are pre- 

 sent, they will accompany the thallium. The former can readily be 

 dissolved out by warm dilute sulphuric acid, which has scarcely any 

 solvent action on the sulphide of thallium, whilst this in its turn can 

 be separated from the sulphide of mercury by being boiled in mode- 

 rately dilute nitric acid, in which the sulphide of mercury is insoluble. 



