190 Mr. W. W. J. Nicol on the Molecular 



Again: — 



BaCl 2 + K 2 S0 4 = BaS0 4 + 2KC1. 



Mol. vol. of BaCl 2 . . . 3626-5 



„ „ K 2 S0 4 . . . 3637*6 



7264-1 



Mol. vol. of BaS0 4 . . . 51-8 



„ „ 2KC1 + 5400 . 7257-1 



7308-9 

 7264-1 



Difference . . = 44-8 



The value found by experiment was 43*7 ; just one unit 

 lower, due to the contraction produced by the dilution of the 

 2NaCl or 2KC1 solution by the 3600 water set free in the 

 reaction. The density of BaS0 4 (solid) was taken as 4*5. 



The above proves most clearly the accuracy of the values 

 given in Table II., and the justice of my statement that the 

 volumes of the metals and acid radicals are independent of the 

 mode of combination. It also appears from the preceding 

 Tables that the volume occupied by a metal, for instance, is 

 the same whether it be combined with a monatomic or dia- 

 tomic acid radical. The cause of this may be that in a solu- 

 tion there are aggregations of two or more molecules* ; but I 

 must reserve this point for future discussion. 



Further evidence in support of the constancy of the mole- 

 cular or atomic volume is to be found in the results of expe- 

 riments by Ostwaldt, on the volume-change on neutralization 

 of certain acids, organic and inorganic, by potash, soda, and 

 ammonia. He found the difference in volume-change between 

 KHO and NaHO, and between NaliO and NH 4 HO, remained 

 a practically constant number. His results are given in 

 Table VII., along with the values I have found for some of 

 the same reactions. Now since 1 have shown above that the 

 difference (K— Na)R is constant for H 2 S0 4 , HC1, and HN0 3 , 

 it follows that this also holds good for all the salts examined 

 by Ostwald, and that the molecular volumes of the salt-radicals 

 are also constant. 



* Meyer, Die modernen Theorien der Chemie, 5th edit. p. 321 &c. 



f Meyer, he, cit. p. 453: and Oswald, Journ.f.prakl, Chemie, 1877, &c. 



