524> Dr. Andrews's Report on the Heat of Combination, 



Acetate of Lead and Sulphate of Soda^^'*-'^^^'^'^ 



o b 



feraperature of air 12'3 12*2 



Inerernents observed 0'84< 0*86 



Heat for 1 grm. PbO, SO3 8-3 , , , 8;^„ , ,^^ 



Heat for J equiv. PbO, SO3 . . 159-?, „« b„y noifit 



Acetate of Lead and Sulphate of Zinc. 



00 

 Temperature of air 12"3 13'9 



Increments observed 0"41 0*37 



Heat for 1 grm. PbO, SO3 4*1 3'7 



Heat for 1 equiv. PbO, SO3 . . 73-9 ^^^ 



In the last experiment the precipitation was so slow that the ther- 

 mometer did not attain the highest point for thirteen minutes after 

 the solutions were mixed. 



When the salts of lead are precipitated by a neutral oxalate, the 

 beat disengaged is much greater than when they are precipitated by 

 a sulphate. I have not examined in detail the increments of tem- 

 perature in this class of precipitations, but in one experiment, in 

 which the acetate of lead was precipitated by the oxalate of potash, 

 36"2 units of heat were obtained for each gramme of oxalate of lead. 



In the experiments next to be described, a dilute acid was substi- 

 tuted for one of the neutral solutions. 



Chloride of Barium and Sulphuric Acid. — The same quantities of 

 chloride of barium and of water were taken as in the experiments 

 with the neutral sulphates. A slight excess of sulphuric acid was 

 employed to secure complete precipitation. 



IBli^ 7,1— .toi'>^ X^\f 000 



ailt Temperature of air ... Mir 17?gn 18-4 15-1 9-8 ■'■ 



viii Increments observed S^i 346 3'38 3*42 ?. 



-i i Heat for 1 grm. BaO, SO,,. . 45-6 45-6 44-0 44-2 



Mbh Heat for I equiv. BaO, SO3 "rfrwdriyl 654*6 i 



Nitrate of Barytes and Sulphuric Acid. — As in the former expe- 

 riments, half the usual equivalents only were taken. 



00 

 Temperature of air 15*0 15'S 



Increments observed 1*50 1*49 



"^^ Heat for 1 grm. BaO, SO3 40-4 39*2 



Heat for 1 equiv. BaO, SO3 . . 580-2 



Acetate of Barytes and Sidphuric Acid, — Half equivalents were 

 taken in this case also. 



o o ■, 



Temperature of air 12*3 12*5 



Increments observed 1*90 1'91 '^ 



Heat for 1 grm. BaO, SO, 49*5 49-3 '^ 



Heat for 1 equiv. BaO, SO, . . 720-2 ^" 



Acetate of Barytes and Oxalic Acid. — 11*2 grms. of lldeialtft^^f 

 barytes and 5*33 grms. oxalic acid taken, q yi379 dguoixU bss^^na 



