Aqueous Solutions of Acids and Alkalies. 297 



In this case the water present is in greater quantity than 

 would suffice to fill the decigallon measure if water alone was 

 present. The 5° of acid (25'05S grs.) condense their own 

 volume and *1203 septem besides. The effect produced by 

 100° of acid, or 1 test atom, is of course 20 times as much, 

 namely, 2*406 septems. I have put this and similar negative 

 quantities in the table with the minus sign ( — ) prefixed to them. 



By this calculation we effect a complete analysis of the so- 

 lution. We begin with — 



the volume"! c , , , , • 



• Li. p-or the solution, 

 the weight J * 



and we find the volume! c , fc . 



i.u • ^i rot the water, 

 the weight J * 



and the volume! r , , , , . j 



4.L • n r oi the anhydrous acid, 

 the weight J J 



The numbers in column 6, which represent the condensa- 

 tion that takes place, are found by subtracting the numbers 

 contained in column 5 from the number which represents the 

 volume of the test atom of uncombined acid SO 3 , which 

 number is placed at the head of column 5. 



The numbers in column 6 represent the actual condensa- 

 tion effected in each mixture by the chemical power of one 

 test atom of SO 3 . I do not mean to ascribe the diminution 

 of bulk to the acid, but to the compound which the acid 

 helps to form. There is consequently a fallacy in the state- 

 ments given in column 5. It is not absolutely true that SO 3 

 occupies the volume there assigned to it in different solutions. 

 It is only true if the actual condensation that occurs is 

 reckoned solely upon the acid, and none ascribed to the water 

 or the resulting hydrate ; but in reality the hydrate alone 

 suffers the whole condensation. This compound has the 

 property of existing, at a given temperature, within a smaller 

 volume than that occupied by its uncombined elements. 

 None of the condensation therefore can be properly ascribed 

 either to the acid or to the water individually. This being 

 understood, the fallacy in the table can lead to no error. 

 The plan adopted has the advantage of rendering the effects 

 of different substances acting on water readily comparable 

 with one another. 



The numbers contained in column 7 represent the atomic 

 volume of the different solutions, that is to say, the volume 

 of solution that contains a test atom of the anhydrous acid. 

 To find these numbers we divide 1000 by the numbers con- 

 tained in column 3 } or by the degree expressed in test atoms. 



The numbers contained in column 4, which represent the 

 state of hydration expressed in atomic proportions, are deter- 



Phil. Mag, S. 3. Vol. 29. No. 194. Oct. 1846. X 



