1885.] 



on the Heat of Dissolution of Salts. 



Sodium Sulphate, Na 2 SO 4 10H 2 O in 190 molecules of Water, or 322 

 parts by weight in 3420 parts of Water. 



Weight of Salt used . . . . 8 *05 grams. 

 Weight of Water used . . . . 85 "5 



Specific Heat of Solution Na 2 SO 4 .200H 2 O = -955. 



Water 

 equiv. 

 calorim., 

 &c. 



Temperature. 



Correction. 



Total 

 change. 



Molecular 



heat of 

 dissolution. 



Mean. 



Before 

 solution. 



After 

 solution. 



1214 

 121 1 

 121-4 

 121-3 



16 -390 

 16*250 

 34-180 

 48*150 



12 *945 

 12 -800 

 34-040 

 48 *200 



■*• *255 

 + *300 



- *0 14 



- *004 



-3*700 

 -3*750 

 -0*136 

 + *046 



-17939 

 -18131 

 - 660 



+ 223 



-18035* 



- 660 

 + 223 



Sodium Carbonate, Na 2 CO 3 .10H 2 O, in 180 molecules, or 286 parts in 

 3240 parts by weight of Water. 



Weight of Salt used . . . . 7 '150 grams. 

 Weight of Water used. . . . 81 "00 



Specific Heat of Solution NaCO 3 .190H 2 O-= '950 approximately. 



Water 

 equiv. 

 calorim., 

 &c. 



Temperature. 



Correction. 



Total 

 change. 



Molecular 



heat of 

 dissolution. 



Mean. 



Before 

 solution. 



After 

 solution. 



117*3 

 116*1 

 116*1 

 116-1 

 116*1 

 116*1 

 116*1 



15 025 

 34 -820 

 34 -300 

 39 *390 

 47*710 

 48 -040 

 48 *230 



12 020 

 34-500 

 34 -050 

 39 300 

 47*690 

 48 *100 

 48*300 



+ 1312 



- -014 

 + -005 

 + '0075 





 



- -005 



-3*1362 

 •306 

 •255 

 •0975 

 •020 



+ 0-062 

 •075 



-14714 



- 1405 \ 



- 1171 J 



- 446 



- 91 

 + 2751 

 + 347 J 



-14714 



- 1288 



- 446 



- 91 



+ 311 



The very rapid decline in the heat absorption attending the solu- 

 tion of these two salts cannot be accounted for by Person's principle, 

 whatever value be considered probable for the specific heat of the solid 

 salt. 



The process of dissolving a solid in a liquid must be considered as 

 involving several distinct operations. Person seems to have been the 

 first to point out that the change of state from solid to liquid must 



* Thomsen's figure at 18° is -18509. 



