Aqueous Solutions of Acids and Alkalies. 301 



effected by 1 atom of SO 3 (or of any other substance) is that 

 which occurs when it combines with the largest possible 

 quantity of water. The extent to which this holds true is 

 best seen on examining the specific gravity of a very dilute 

 solution, for example, that of 1° : 



1*00000000 = specific gravity of water. 



0*00035 252= fraction indicating the mean specific 



gravity of 1° of acid. 

 0*00104748= increase of specific gravity due to 



condensation. 



1*00 140000= real specific gravity of acid of 1°. 



The effect produced by condensation is here three times as 

 great as that due to the mere difference of weight between 

 the anhydrous acid and the water which it replaces. 



The common attribution of the greatest condensation to 

 the third hydrate is nevertheless true, provided we take the 

 protohydrate as the point of comparison. Thus, 47'437 sep- 

 tems of SO 3 , H 2 added to 16*07 septems of water = 63*507 

 septems, whereas the atomic measure of SO 3 + 2H 2 is only 

 58*276 septems, showing a condensation of 5*231 septems. 

 Again, 47*437 septems of SO, H s O added to 32*14 septems 

 of water = 79*577 septems, whereas the atomic measure of 

 SO 3 + 3H s O is 73*403 septems, showing a condensation of 

 6*174 septems, which exceeds the former condensation by 

 0*943 septems. 



The extent to which the mean specific gravity of a solution 

 is increased by condensation depends necessarily on the ac- 

 tual amount of the condensation. As it is easy to ascertain 

 that amount, it will be proper to point out the exact relation 

 between condensation and the term expressing the real spe- 

 cific gravity of a solution. 



If we suppose 500 septems of acid to combine with 500 

 septems of water, and to condense so much as to form only 

 999 septems of solution, we shall require 1 septem more of 

 water to fill the standard measure of a decigallon. This adds 

 7 grs. to the weight of the solution, and therefore increases 

 its specific gravity by *001. If the condensation is such as 

 to require 5 septems of water to complete the decigallon mea- 

 sure, the weight of the liquor will be increased by 35 grs. 

 and its specific gravity by *005. For every septem of con- 

 densation per decigallon, that is to say, for the condensation 

 of every thousandth part by measure of the solution, the in- 

 crease in specific gravity will be *001. This law is universal. 

 The nature of the chemical substance that causes the con- 

 densation, the quantity of it contained in the solution, its 



