300 Mr. Griffin on the Constitution of 



plies to solutions of all substances, and has therefore a general 

 interest. 



If we deduct 1 from the specific gravity of anhydrous 

 sulphuric acid, and divide the residue by the number of test 

 atoms of anhydrous acid that fill a decigallon at 62° F., the 

 product is a fraction, which, when added to 1, represents the 

 mean specific gravity of a solution containing 1 test atom of 

 acid per decigallon. Thus — 



sp.gr. l-97-l _ -97 _. Q35252 



2y5l6 "27-516- ° 35252 ' 



The product -035252+ 1 = 1'035252 is the mean specific gra- 

 vity of a solution of acid of 100°. 



The same decimal fraction multiplied by any given number, 

 say 20, and then added to 1, gives the mean specific gravity 

 of a solution of the chemical strength indicated by the given 

 number. Thus — 



(-035252 x 20) + 1 = 1'70504, 

 which is the mean specific gravity of a solution of acid of 

 2000°. 



If now we compare the mean specific gravities thus calcu- 

 lated with the real experimental specific gravities of the 

 several solutions, and take the differences, we obtain a series 

 of numbers which show the precise extent to which the spe- 

 cific gravities are increased by the condensation resulting 

 from the chemical action of the acid upon the water. I give 

 these differences in the following Table. 



Table III. Showing the increase of Specific Gravity occa- 

 sioned in Solutions of SO 3 by condensation. 



It is commonly stated, in reference to the hydrates of sul- 

 phuric acid, that the greatest condensation occurs in the for- 

 mation of the hydrate S0 3 + 3H 2 = 13G2-3°; but this table 

 shows that the greatest condensation occurs in the formation 

 of the hydrate S0 3 + 2H 2 0=1716°. What I mean by the^ 

 greatest condensation is that which occurs in a given mass of 

 solution ; for, speaking absolutely, the greatest condensation 



