1885.] 



on the Heat of Dissolution of Salts. 



407 



Then Q T =1503 when T=40°. 



= 1537 when T =42°. 

 = 1572 whenT=44°. 



From 40° to 44° observed 1494. 



There is not much difference here, but the observed is less than 

 the calculated number. 



Carbonate of sodium was next examined on account of its close 

 resemblance to sulphate of sodium in water of crystallisation, melting 

 point, and solubility. 



Sodium Carbonate, Na 2 C0 3 , in 100 molecules of Water, or 106 parts 

 in 1800 parts by weight. 



Weight of Salt used . . - . 5 '005 grams. 

 Weight of Water used.. ..85-0 



Specific Heat of Solution ^a 2 CO 3 .100H 3 O=-933. 





Water 



Temperature. 









Number 









Total 

 rise. 



Molecular 



of 

 expt. 



equiv. 

 calorim., 

 &c. 



Before 



After 



Correction. 



heat of 

 dissolution. 



solution. 



solution. 









26 



116-2 



21-85 



24-37 



+ -075 



2-595 



6388 



27 



116-3 



21-80 



24-25 



+ -058 



2-508 



6177 



28 



117-5 



22 -545 



25 '050 



+ -1075 



2-6125 



6485 



29 



117-4 



22-39 



24-82 



+ -079 



2-509 



6238 



30 



116 -2 



35-60 



38-40 







2-800 



6887 



31 



116 -2 



35-28 



38 -08 







2-800 



6887 



32 



116-2 



35-70 



38-50 







2-800 



6887 



33 



116-3 



38-18 



40-90 



+ -004 



2-724 



6708 



34 



116 3 



38 -97 



41 -60 



+ -112 



2-742 



6753 



35 



116-1 



43-55 



46-30 



+ -015 



2-765 



6785 



36 



116-3 



50 -40 



53-16 



+ -020 



2-780 



6846 



37 



115-1 



55-25 



58-08 







2-790 



6783 



38 



114 -9 



54-73 



57-58 







2-850 



6923 



39 



116 1 



54 -60 



57-50 



- -002 



2-898 



7128 



40 



116-2 



54-30 



57-18 







2-880 



7067 



41 



115-1 



56-00 



58 -875 







2-875 



7004 



The carbonate of sodium used in these experiments had been 

 heated to redness, but at times which varied from a few hours to 

 several days before the experiment. Some of the irregularities in the 

 numbers may be not improbably due to this circumstance. But the 

 mean results show on the whole an increase in the heat of dissolution 

 with rise of temperature. 



