CHEMICAL SCIENCE. 199 



salts is also changed. The acid of the salt is to be regarded as uniting 

 directly with the metal, and not wiih its oxide, according to the old system, 

 the oxygen of the oxide being referred to the acid. Thus nitrate of silver, 

 on the old system, was written XQj + AgO; but, according to the new sys' 

 tern, the metal takes the place of the hydrogen in the acid, and it is expressed 

 NOsAg. 



ON THE INFLUENCE OF PRESSURE ON CHEMICAL AFFINITY. BY 



DR. LOTHAR MEYER. 



In the twelfth volume of Poggendorff s Annalen, there is a note by Babinet, 

 which contains the proposal to use, as a measure of chemical affinity, the 

 pressure which a gas generated by chemical decomposition must attain in 

 order that the decomposition may cease. The author states that for zinc and 

 sulphuric acid the limit is reached when for O 3 C., the pressure of the liberated 

 hydrogen amounts to thirteen atmospheres; at 2^ C., on the contrary, this 

 pressure exceeds the height of thirty-three atmospheres. 



Experiments which I have made in Prof. Wcrther's laboratory do not agree 

 with these statements. With the most varied strengths of sulphuric acid, 

 even in the presence of large quantities of different sulphates, and by the use 

 of citric and acetic acids, the pressure of the hydrogen liberated by zinc far 

 exceeds the limits given by Babinet. The reason of this appears to lie in 

 the fact, that Babinet used copper vessels closed by a cock, while I used sealed 

 glass tubes. 



The decomposition appears, however, to attain- a limit ; at any rate, the 

 liquid, even with excess of zinc, has still a strong acid reaction after stand- 

 ing for months. But what the maximum of this pressure may be, I have 

 not been able to determine, inasmuch as the only tubes I could obtain which 

 would stand the pressure were too narrow to allow a manometer to be intro- 

 duced. The greatest pressure which I -observed directly at the manometer 

 was sixty-six atmospheres. The acid consisted of one volume SH->04, and 

 three volumes of HaO; the temperature was C. The tube exploded 

 shortly after observing this pressure. Poggendorff' s Annalen, vol. civ., p. 

 189. 



FURTHER OBSERVATIONS ON THE ALLOTROPIC MODIFICATIONS OF 

 OXYGEN, AND ON THE COMPOUND NATURE OF CHLORINE, BRO- 

 MINE, ETC. 



The following remarks on the above subject, were addressed as a letter by 

 Professor Schonbein, to Professor Faraday, and by him communicated to 

 the L. E. and D. Phil. Mag., xvi., 178: 



These last six months I have been busily working on oxygen, and flatter 

 myself not to have quite in vain maltreated my old favorite; for I think I 

 can now prove the correctness of that old idea of mine, that there are two 

 kinds, or allotropic modifications of active oxygen, standing to each other 

 in the relation of + to ; i. e., that there is a positively active and a nega- 

 tively active oxygen, an ozone and an antozone, which, on being brought 

 together, neutralize each other into common or inactive oxygen, according 



o o 



to the equation (+ O) + ( U) = O. At present I confine myself to general 

 statements ; but a full detail will, before long, be published in the Transac- 

 tions of the Academy of Munich. 



