NICCOLITE. 101 



nitrate of potassa and 2 parts of carbonate of soda, in 

 a platinum crucible, the bottom and sides of which 

 have previously been carefully covered with carbonate 

 of soda; the mass is then ignited for some time, and 

 when cold is digested with water ; the oxides formed 

 are filtered off and thoroughly washed. 



The solution contains all the arsenic in the form of 

 arsenates of the alkalies; it is supersaturated^ with 

 hydrochloric acid, and then mixed with concentrated 

 caustic ammonia and sulphate of magnesia. 



After twenty-four hours the precipitate is collected 

 on a weighed filter, washed with dilute caustic am- 

 monia, dried at 100 and weighed. (See No. 51.) 



The arsenic may also be determined from the loss. 



The oxides are dissolved in concentrated hydro- 

 chloric acid, and the copper and bismuth precipitated 

 from the solution by sulphuretted hydrogen. The 

 precipitate is treated as in No. 50. 



The liquid filtered off from the precipitate is heated 

 nearly to boiling, and mixed with some chlorate of 

 potassa in order to peroxidize the iron, which may 

 then be separated from the nickel and cobalt in the 

 same manner as from manganese, either by'succinate 

 of ammonia or by carbonate of baryta. (See No. 25.) 



From the liquid filtered off from the succinate of 

 iron, nickel and cobalt are precipitated at a boiling- 

 heat by caustic potassa, filtered off, and washed witk 

 hot water. 



From the liquid separated from the carbonate of 

 baryta, the dissolved baryta is precipitated by sul- 

 phuric acid, and the nickel and cobalt are then pre- 

 cipitated from the hot solution by caustic potassa. 



The precipitate containing the hyd rated oxides of 

 nickel and cobalt is gradually mixed, whilst still moist, 

 with dilute hydrocyanic acid and solution of potassa 

 (or cyanide of potassium), and a gentle heat applied 

 until it is dissolved. The yellowish-red solution is 



