418 Mr. Graham on the Heat disengaged in Combinations. 



Doubling 3°*35, the mean result, there is obtained 6 o, 70 as 

 the heat disengaged on saturating the second proportion of 

 carbonic acid in the bicarbonate of potash. 



One equivalent, 62*76 grains, of the crystallized bicarbonate 

 was dissolved in 100 grammes of water at 67°, with a fall in 

 three experiments of 3 0> 68, 3 0, 69 and 3°*74 ; mean 3°*70. 



One equivalent of anhydrous carbonate of potash was dis- 

 solved in 100 grammes of water at 67°, with a rise in three 

 experiments of 2°-48, 2°*43 and 2°«47 ; mean 2 0, 46. The heat 

 evolved on dissolving anhydrous acetate of potash is nearly 

 the same, being 2°*45. 



VII. Neutralization of Arsenic and Phosphoric Acids by 



Hydrate of Potash. 

 Half an equivalent of arsenic acid, 36'00 grains, in solution 

 as usual, was mixed with exactly half an equivalent of hydrate 

 of potash, to form the binarseniate of potash (2 HO, KO, 

 AsO s ):— 



Before mixture . . 63°*04 63°-19 63°-29 



After mixture . . . 68°-14 68°-30 68°-38 



Rise of temperature . 5°-10 5°-ll 5 o, 09 



Doubling 5 o, 10, the mean result, we obtain 10°*20 F. as 



the heat disengaged by neutralizing 1 equivalent of potash in 



the formation of binarseniate of potash. 



One-fourth of an equivalent of arsenic acid, 18*00 grains, 

 was mixed with exactly half an equivalent of potash, to form 

 arseniate of potash (HO, 2KO, AsO s ) : — 

 Before mixture . . 63°-27 63°*33 63 0, 42 

 After mixture . . . 67°'87 67°'94 68°-Q5 

 Rise of temperature . 4°*60 4°-61 4°*63 Mean 4°*61. 

 Twice 4°*61, or 9°*22 R, is therefore the heat disengaged 

 on neutralizing 1 equivalent of hydrate of potash in the for- 

 mation of the neutral arseniate of potash. 



The same salt was formed by mixing together solutions of 

 half an equivalent of binarseniate of potash, 56*37 grains, and 

 exactly half an equivalent of potash : — 



Before mixture . . 64°*28 64°-27 64°*20 



After mixture . . . 68°-31 68°-33 68°-26 



Rise of temperature . 4°-03 4°-06 4°-06 



Taking 4 o, 05 as the mean, we have twice that quantity, or 



8 o, 10 F., as the heat disengaged on neutralizing 1 equivalent 



of potash with the acid in binarseniate of potash. 



On forming the subarseniate of potash (3KO, As0 5 ), by 

 mixing together solutions of one -sixth of an equivalent of 

 arsenic acid and exactly half an equivalent of potash : — 



