522 Dr. Andrews's Report on the Heat of Comhinaiion. 



sufficient to decompose completely the chloride of barium. The en- 

 tire weight of the water employed to dissolve the salts was 234 grms., 

 of which one-third was taken to dissolve the sulphate of magnesia, 

 and two-thirds to dissolve the chloride of barium. The solutions 

 were contained in vessels of thin copper, the smaller of which, when 

 filled with its solution, floated in the larger, and could be rapidly 

 rotated, so as to produce in a short time a perfect equilibrium of 

 temperature throughout the whole apparatus. The thermometer 

 attained a maximum about 8' after the solutions were mixed. I have 

 elsewhere indicated the precautions to be taken in such experiments, 

 and shall therefore not refer to them here. In the following state- 

 ments, I have given the temperature of the air, the increment ac- 

 tually observed in Centigrade degrees, and the number of degrees 

 through which 1 grm. of water would be raised by the precipitation 

 of 1 grm. and 1 equiv. (oxygen = 1) of the precipitate. In calcu- 

 lating the latter numbers, all the usual corrections were applied to 

 the observed increments of temperature : — 



o o 



Temperature of air 18*3 M'^ 



Increments observed 1*95 I '96 



Heat for 1 grm. BaO, SO,, 25-4 25-2 



Heat for 1 equiv. BaO, SOg . . 368'9 



Chloride of Barium and Sulphate of Soda. — The same weight of 

 chloride of barium taken as before, and an equivalent weight of sul- 

 phate of soda. 



o o 



Temperature of air 20*2 18'7 



Increments observed I "57 l'5!i 



Heat for 1 grm. BaO, SO, .... 20-4 201 



Heat for 1 equiv. BaO, SO3 . . 294'5 



Chloride of Barium and Sulphate of Zinc. 



00 



Temperature of air 19*7 19*6 



Increments observed 1*69 1*72 



Heat for 1 grm. BaO, SO3 .... 22*2 22*4 



Heat for 1 equiv. BaO, SO3 . . 325-1 



Chloride of Barium and Protosulphate of Iron. 



o 



Temperature of air 18-8 



Increment observed 1*99 



Heat for I grm. BaO, SO, 25*6 



Heat for 1 equiv. BaO, SO3 373*2 ,.,, 



Chloride of Barium and Sulphate of Copper. ^ 



Temperature of air 17*5 17*6 



Increments observed 1*85 1*85 



Heat for 1 grm. BaO, SO3 24*7 24*6 



Heat for 1 equiv. BaO, SO3 . . 359*4 



