416 Mr. Graham on ike Heat disengaged in Combinations. 



0°'68, 0, 68; mean 0°*68 F. If it were therefore possible to 

 dissolve a whole equivalent of the salt in a whole equiva- 

 lent of the acid contained in the quantity of water to which 

 we are restricted, the fall would be four times greater, or 

 2°*72 F., which is nearly the same as the cold on dissolving 

 crystallized oxalate of potash in water, namely 2°*66. Here 

 again little or no heat is observed in forming a double salt, for 

 the binoxalate of potash must be regarded as such. 



Binoxalate of Potash. KO, C 2 O s + HO, C 2 3 , 2 HO.— 

 As with bisulphate of potash, the saturation of the excess 

 of acid in this salt causes the disengagement of more heat 

 than the saturation of the same quantity of free acid. One- 

 fourth of an equivalent of the crystallized binoxalate, 22*91 

 grains, was neutralized by hydrate of potash at 67°: — 



Before mixture . . 66°*80 66°*85 66°*96 

 After mixture . . . 69°*91 69°*96 70°*04 

 Rise of temperature . 3°*11 3°-ll 3°*08 Mean 3°*10 



The mean quantity, multiplied by four, gives 12°*40 F., 

 as the heat evolved on neutralizing by potash the second 

 equivalent of oxalic acid in binoxalate of potash. Now dis- 

 tributing the heat from the saturation of two equivalents of 

 oxalic acid, 20°*68 ( = 10 o, 34 x2), as was done in sulphuric 

 acid, we have — 



Heat disengaged in the formation of binoxalate of pot. 8°*28 

 in saturating acid of binoxalate of pot. 12 o, 40 



20°-68 



One-fourth of an equivalent of binoxalate of potash, 22*91 

 grains, containing 6*25 grains of water of crystallization, was 

 dissolved in 1538 grains of water at 64° F., with a fall of 1°*65, 

 1°*66, 1°*65 ; mean 1°*65 F. The mean result multiplied by 

 four, gives 6°*60 F, as the fall on dissolving a whole equivalent 

 of binoxalate of potash in water. This is 0°*89 more than the 

 sum of the falls on dissolving the constituent salts separately, 

 2°-66 + 3°*05 being equal to 5°*71 only. 



Quadr oxalate of Pot ask. KO, C 2 O s + HO, C 2 O a + 2 

 (HO, C 2 3 + 2HO). — Four-sixths of an equivalent of hy- 

 drated oxalic acid, 26*22 grains, were mixed with one-sixth 

 of an equivalent of potash exactly to form this salt: — 



Before mixture . . 64°*25 64°*23 64°*25 

 After mixture . . . 66°*01 66°'Q1 65°*99 

 Rise of temperature . 1°*76 1°*78 1°*74 



The mean result 1°*76 multiplied by six, gives 10 o, 56 as the 

 heat evolved in the formation of quadroxalate of potash; that 

 is, in the saturation of 1 equivalent of potash by 1 of oxalic 



