ISO THALLIUM. 



sulphide of ammonium, in caustic alkalies, their car- 

 bonates and cyanides, and only slightly soluble in 

 acetic acid. Hydrochloric acid and soluble chlorides 

 precipitate a difficultly soluble white chloride ; hydro- 

 bromic acid and bromides precipitate a white nearly 

 insoluble bromide ; and hydriodic acid and iodides an 

 insoluble yellow iodide. Alkalies and alkaline car- 

 bonates produce no change in salts of the protoxide ; 

 phosphate of soda gives a white precipitate, nearly in- 

 soluble in ammonia, easily soluble in acids. Chromate 

 of potassa gives a yellow precipitate of chromate of the 

 protoxide. Bichloride of platinum precipitates a very 

 pale yellow insoluble double salt. 



From these reactions it appears that in examining 

 a mixed metallic solution, according to the ordinary 

 method of qualitative analysis thallium will be found 

 in the precipitate thrown down by sulphide of ammo- 

 nium, together with iron, nickel, manganese, &c. From 

 these metals it may be easily separated by precipitat- 

 ing with iodide of potassium, or bichloride of platinum, 

 or by reduction to the metallic state by zinc. Iodide 

 of potassium is next to the spectral reactions the 

 most delicate of all tests for thallium. 



3. Salts of the sesquioxide are easily distinguished 

 from those of protoxide by their behavior with alkalies, 

 and with soluble chlorides or bromides. Their solu- 

 tions give, with ammonia, and with fixed alkalies and 

 their carbonates, a brown, gelatinous precipitate of 

 sesquioxide, containing the whole of the thallium. 

 Hydrochloric acid and soluble chlorides or bromides 

 produce no precipitate in solutions of pure salts of the 

 sesquioxide ; but if any protoxide is likewise present 

 a sesquichloride or sesquibromide is formed. Chro- 

 mate of potassa produces no precipitate, except in a 

 solution of sulphate. 



V. Estimation and separation. Thallium, when it 

 occurs in solution as a salt of the protoxide, is most 



