404 Mr. Graham on the Heat disengaged in Combinations. 



On the other hand, the cold, on dissolving several equiva- 

 lents of nitrate of potash successively at a constant tempera- 

 ture, in the same quantity of water diminishes considerably 

 with the number of equivalents of salt dissolved. The capa- 

 city for heat of the crystallized salt is 0*239 (Regnault). 

 Dissolved in 1544 grains of water, 

 First equivalent of nitrate of potash : — 

 62°'34 63°*68 



56°-68 57°-90 



Fall 5°-66 5°-78 Mean 5°'72. 



Second equivalent of nitrate of potash: — 

 63°-47 63°- 12 



58°-17 57°'86 



Fall 5°-30 5°-26 Mean 5°'28. 



Third equivalent of nitrate of potash : — 

 63°-40 63°'S6 



58°-47 58°-61 



Fall 4°-93 4°-95 Mean 4°'94. 



Fourth equivalent of nitrate of potash : — 

 63°*57 63°-35 



58°-95 58°-76 



Fall 4°-62 4°-59 



Fifth equivalent of nitrate of potash : — 

 63°*40 63°-34 



59°'Q8 59°-10 



Fall 4°-32 4°-24 Mean 4°-28. 



Sixth equivalent of nitrate of potash : — 

 63°*45 

 69°-63 

 ^ Fall 3°-82 

 In consequence of this diminished absorption of heat in the 

 solution of the latter equivalents of nitrate of potash, the ad- 

 dition of water to the strong solution finally obtained occa- 

 sions a further absorption of heat; or dilution produces cold. 

 The last prepared solution, which consisted of 379*5 grains 

 of nitrate of potash dissolved in 1544 grains of water, and is 

 a solution nearly saturated for the temperature, was mixed 

 with another 1544 grains of water in a pint silver crucible 

 with silver spatula, weighing 1650 grains, both liquids being 

 at the same temperature : — 



Before mixture . . 63°*19 

 After mixture . . . 61°'91 

 Fall of temperature . 1 0, 28 



