HYDRATES AND CARBONATES OF THE ALK ALT-METALS, ETC. 461 



it was purified in the following manner : — A solution of the salt in water was poured into 

 a solution of more than the calculated weight of tartaric acid in water acidulated with 

 hydrochloric acid, the bitartrate allowed to settle, collected on a funnel over a small 

 filter, and washed with small instalments of water, until the last washings were free of 

 chlorine, when it was assumed that the small quantity of soda which the salt undoubtedly 

 contained had passed into the filtrate ; the function assigned to the hydrochloric acid was 

 to convert any calcium that might be present into chloride. 



The washed bitartrate was dried and heated in a covered platinum basin over a large 

 flame, until all the organic matter was apparently destroyed ; the black mass was then 

 treated with water, the charcoal filtered off, the filtrate treated with washed carbonic acid, 

 until every trace of caustic alkali that might have been formed was sure to have been 

 converted into, at least normal, carbonate, and then evaporated in platinum to dryness. 

 The residue was made into a coarse powder, kept in a covered platinum vessel over a 

 Bunsen at a temperature just short of the fusing-point of the salt, with occasional turn- 

 ing over with a platinum spatula, and then preserved for the experiments. In the course 

 of these it was observed that the caustic potash produced volatilised far more readily than 

 the caustic soda had done in the previous trials with its carbonate, so that the outlet tube 

 of the hydrogen crucible not unfrequently got clogged up, and had to be cleared by 

 applying a special lamp and introducing a stout red-hot wire, to assist the hydrogen in 

 blowing out the liquid alkali. 



Experiment I. — 1*67 14 grm. of dry carbonate of potash were mixed with spongy 

 platinum, and the mixture, after having been put into a platinum foil cornet, heated 

 within the gas-crucible in hydrogen for an hour and a half. Weight of product (as far 

 as in the cornet after the heating process) = 0*4892 grm. Carbonic acid in it, 0*1422 ; 

 sulphate obtained = 0*6474. Hence, by calculation, 



Carbonate of potash, K 2 C0 3 , . . . . . 91*346 



Oxide of potassium, K 2 0, ..... 9*286 



100*632 



The apparent absence of alkali hydrate, KHO, in the product causes me to look 

 upon this analysis with suspicion ; I give the experiment for what it may be 

 worth. 



Experiment II. — In this experiment 9*45 grm. of carbonate of potash were used and 

 placed direct in the crucible, without spongy platinum. The blowpipe was again used 

 from the first, and the heating continued for an hour and a half. The product was 

 analysed twice : — 



Substance taken, ..... 

 Carbonic acid obtained, .... 

 Sulphate of potash obtained, 



VOL. XXXV. PART II. (NO. 12). 



(1) 



(2) 



1*835 



1-676 grm. 



0-5323 



0*4861 



2-3468 



2*1452 





4 G 



