ON THE SPECIFIC GRAVITY OF SULPHURIC ACID. 
15 
The mean error in this series of experiments is consequently equal to 4-’676, 
and the most probable error of a single observation = S‘151.. 
Regarding the heat evolved by one atom of concentrated acid (SO»+ H,0), 
for which Hess in another series of experiments has found the value to be 
229‘41, thb acid should, if it followed the same law as the other hydrates, 
produce six portions of heat or 278'4'1, and the diflerence between the ob¬ 
served and calculated value would bo equal to -- 5(K). Hess supposes there¬ 
fore that it only produces 5 portions of beat, or 232*01, and the same difference 
will only be — 2*50. 
If now we suppose that the diffused heat is proportionate to the maximum 
of coutraction of an acid, which in one atom SO- contains n atoms water, or 
if we put 
= .( 11 .) 
where W is the quantity of beat evolved by the acid employed, anil C the 
maximum of contraction calculated before (Table V.), we obtain for the de¬ 
termination of ?n the following equations:— 
Table X. 
n. 
1 W mC. 
W calculated. 
1 A. 
2 
134*20 = 0*038819« 
139*36 
~5*I6 
3 
94*18 = 0*025809« 
92*65 
4- 1*52 
4 
77*23 = 0*019330ffi I 
69*40 
4- 7*83 
6 
48*94 = 0*0l2869w | 
46*20 
+ 0-74 
The most probable value for m will he 
m = 3590*0 + 71*25, 
and the probable error of a single observation = 3*71. 
A like result will be obtained, if for W is taken the values of the 
ot contraction directly found In Table IV., which give tlio equations 
maxima 
Table XI. 
n. 
1 W=m'C. 
W calculated. 
A. 
2 
134*2 = 0*032266m' 
130*16 
+ 4*04 
3 
94*18 =0-023I95w' 
98*57 
+ 0-61 
4 
77*23 = 0-OI9265W' 
77*72 
— 0*49 
6 
46*94 = 0*014028t«' 
56*59 
-9*65 
from which we obtain m' ~ 4034*14. + 86*49, and the probable error of a 
wngle observation 4*01. “ 
As the probable error in these two cases is very slightly different from the 
uncertamty of the values of the quantities of heat calculat'd according to 
of Hess, it may be supposed with the same degree of proba- 
biiity, that the heat evolved by a certain hydrate of sulphuric acid on the 
ditioo of aa excess of water is proportionate to the maxiitiuni of con- 
ractioD of the same hydrates; or that both are inversely proportionate to 
the number of atoms of water which the acid employed coutnms corabiued 
With one atom of pure acid. 
This law at least ajipuars to hold good for the larger degrees of dilution, 
egarding tlie acid SO 3 11,0, Hess supposes, as previously stated, that it 
