242 Johnston and Adams — Hiah Pressures on th 



le 



Attention is directed to the first line* of Table YI, in refer- 

 ence to which Spring writes as follows : 



a When the mixture had been compressed for some instants to 

 about 6000 atm., it was found that 59*16 per cent of the quantity 

 of barium carbonate had been transformed into barium sulphate. 

 This transformation is not, however, the exclusive result of 

 compression ; for the mixture obtained by shaking, but not yet 

 compressed, when analyzed under the same conditions, furnished 

 49*79 per cent of barium sulphate. Moreover, simply by treat- 

 ing an identical weight of barium carbonate with a solution of 

 sodium sulphate, the concentration of which was similar to that 

 produced during the process of analysis, I obtained 40*29 per 

 cent of barium sulphate. By taking account of these circum- 

 stances, one is led to the conclusion that simply shaking dry 

 barium carbonate with sodium sulphate produced 49*79 — 

 40*29 = 9*5 per cent of barium sulphate ; and that the process 

 of compression in turn produced 9*37 per cent." 



To all of this there is one fatal objection : namely, that it is 

 absolutely useless to try to determine equilibrium conditions 

 by means of any process which of itself disturbs the equili- 

 brium. Therefore, the above results show only the relative 

 amounts of the substances after the addition of the water, but 

 can give us no certain information with regard to the actual 

 state of equilibrium between the dry solid phases. 



The truth of this reasoning is perfectly obvious, and so 

 also is the inherent absurdity of the position that the equili- 

 brium conditions between the solid phases may be ascertained 

 by treatment with water. This is illustrated by the fact that a 

 system composed of successive layers of powdered barium car- 

 bonate and sodium sulphate, when treated with water, would 

 show considerable transformation,! although it is certain that 

 the reaction between the solids under such conditions must 

 have been absolutely inappreciable. 



Now it is well known that the system, 



BaC0 3 +Na 2 S0 4 ±^ BaS0 4 + Na 2 C0 3 



when in presence of water, reaches in the lapse of time a state 

 of equilibrium ; indeed it was upon an experimental study of 

 this equilibrium that Guldberg and Waage based the law of 

 mass action. The condition of equilibrium is determined, in 

 accordance with the law of mass action and the most generally 



* Similar control experiments with the reverse reaction showed that only a 

 trace of BaS0 4 was transformed by simply shaking together the two pow- 

 dered components. 



f Indeed this is nearly identical with Spring's experiment in which he 

 treated powdered barium carbonate with sodium sulphate solution, and 

 found that 40 per cent of the carbonate had been transformed into barium 

 sulphate. 



