Mr. Graham on the Heat disengaged in Combinations. 411 



An alkaline chloride was little affected by the presence of 

 an equivalent of these acids in the water in which it was dis- 

 solved. Thus chloride of sodium was dissolved with a fall — 



In lOOOgrs. water, of0 o, 57, 0°-60, MeanO°'59R. 



... + HC1, of 0°'60, 0°-60, 0°'60, ... 0°'60R. 

 ... + N0 5 , of0°*50, 0°-50,0°'52, ... 0°*51 R. 

 ... +S0 3 , of 0°'50, O '50, 0°'43, ... 0°'48R. 



To obtain light upon this influence of acids on the thermal 

 phsenomena of the solution of salts, experiments were made upon 

 two other salts. Sulphate of ammonia without any water of cry- 

 stallization (1 equivalent, or 41*41 grains) was observed to dis- 

 solve in 1000 grains of water with a fall of 0°'5L R. In water 

 containing i HC1, with a fall of 1°-12, 1°-10, and l°-12 R.; 

 mean 1°*1 1. In water containing HC1, with a fall of 1°*30, 

 l°-22, l°-28; mean 1°*27 R. In water containing N0 5 , with a 

 fall of l°-28, 1°*30, l°-30; mean 1°'29 R. In water containing 

 SO 3 ,withafallof0 o -92,0 o, 92,0 o -90; mean0°-92 R. The addi- 

 tion of a second equivalent of highly diluted sulphuric acid to 

 the last solution produced a change of temperature in three 

 experiments of o, 02, 0, 00, 0°'00. The addition of a second 

 equivalent of sulphate of ammonia to the preceding solutions 

 of the bisulphate of ammonia, occasioned a fall of o, 58, o, 55, 

 0, 60 R. ; mean 0, 58, or very little more than in pure water 

 (0 0, 51). In 1544 grains of water containing 1 equivalent of 

 acetic acid (32-15 grains), with a fall of 0°-84, O 0< 78, 0°*81 F., 

 of which the mean is 0°*81 F., the experiment being made 

 at 67° F. In 1 equivalent of oxalic acid (22*64 grains), with 

 a fall of l°-20, 1°*21 and 1°'22 F., the experiment being made 

 at 65° F. To render the last two experiments comparable 

 with the former, they must be reduced in the proportion of 

 19 to 13, that is, the effect of the acetic acid to 0°'55 R., of 

 the oxalic acid to 0°*83 R. ; so that the influence of the acetic 

 acid is almost nothing, of the oxalic acid much less than that 

 of the mineral acids. 



While 1 equivalent of nitrate of potash was dissolved in 

 1000 grains of water at 63° F., with a fall of 3°'76, 3°*72 and 

 3 0, 80 R., of which the mean is 3°*76 ; it was dissolved in the 

 same quantity of water containing 1 equivalent of nitric acid 

 at 67° F., with a fall of 3 0, 64, 3°-54, 3°'64 R., of which the 

 mean is 3°*57 ; in the same quantity of water containing 1 

 equivalent of sulphuric acid at 58° F., with a fall of 3 0, 53, 

 3°-50, 3 0, 50 R., of which the mean is 3°*51. 



The mere mixing of solutions of such neutral salts as are 

 understood to combine together and form a double salt, is not 

 attended with such changes of temperature. No sensible 



