Combination of Sulphuric Acid and Water. 261 



written on the subject ; namely, that the heat evolved 

 when sulphuric acid and water are mixed, is owing to the 

 formation of a new compound, whose specific heat is less 

 than the mean of that of the two constituents ; we must 

 compare the specific heats as above given with the mean 

 specific heats of the compound, supposing no change what- 

 ever to have taken place. This is done in the following 

 table : 



+ 10 



Sp. heats by 

 experiment 



10000 

 0-3593 

 0-4707 

 0-4786 

 0-5228 

 0-5690 

 0-6091 

 0-6428 

 0-6699 

 0-7003 

 0-7201 



Mean sp, 

 heats. 



0-4587 

 0-5326 

 0.5869 

 0-6306 

 0-6660 

 0-6952 

 0-7197 

 0-7405 

 0-7585 



Differences. 



+ 0-0120 



— 00540 



— 0-0641 



— 00616 



— 0-0569 



— 00524 



— 0-0498 



— 0-0402 



— 0-0384 



The slightest comparison of the second and third columns 

 of this table is suflacient to show that the hypothesis of 

 Dr. Irvine cannot be accurate. The specific heat of a com- 

 pound of 1 atom oil of vitriol and 1 atom water is greater 

 than the mean by about -j^ih ; yet, if we turn to the table 

 in page 257, we see that the heat evolved amounts to no less 

 than 185°. Now, it is impossible that this evolution of 

 heat can be occasioned by a diminution of specific heat 

 when no such diminution takes place. In all the other 

 compounds there is a diminution of specific heat, but that 

 diminution by no means corresponds with the quantity of 

 heat evolved. The greatest diminution takes place when 1 

 atom of oil of vitriol is mixed with three atoms of water. 

 It amounts in that case to 0-0641, or very nearly ^th, and 

 the heat evolved is 208°. But, when 1 atom of oil of vitriol 

 is mixed with 2 atoms of water, the heat evolved is 219°, 

 yet the diminution of specific heat is only 0*054 or about 

 -j^th, and consequently less than when the evolution of 

 heat is only 208°. When 1 atom of oil of vitriol combines 

 with 5 atoms of water, the diminution of specific heat is 



