266. oJ. P. Cooke, Jr.—Berthelot’s Thermo-Chemistry. 
gram units. Two series of reactions may now be arranged 
so as to fulfill the conditions we have assumed— 
First Series. 
K,+ Br, (gas) + Aq=(6KBr-+ Aq) 570,000 units. 
Al,+Cl,=AlLCl, 321,800 units. 
Al,Cl, dissolved in (6K Br+ Aq) 152,000 units. 
1,043,800 units. 
Second Series. 
K,+Cl,+ Aq= (6KCl+ Aq) 604,800 units. 
Al,+Br,=Al,Br, x units. 
A1,Br, dissolved in (6KCl+Aq) 173,800 units. 
778,600 units. 
a+ 778,600 =1,043,800. «= 265,200. 
In studying these two series of reactions it will be evident 
that we begin in each case with the same amounts of the sam 
elementary substances, namely: K,, Al,, Br,, Cl,, and that we 
end with aqueous solutions in the same condition. Hence, 
the total amount of heat evolved in each of the two series 
must be the same, and we can at once deduce the value of the 
tes, 
although it would be very difficult if not impossible to form 
these substances with a definite composition in the calorimeter. 
Thus, to determine the heat evolved in the reaction SO, + 
H,O = H,SO,, we have only to dissolve in one experiment SO, 
and in another H,SO, in a comparatively large amount of 
theorem enables us to determine very sup the 
y ra 
