EECENT PROGRESS IN PHYSICS. 6l\) 



and remains in solution. Pure S O4 H (concentrated sulphuric acid) 

 does not afford the water, and the remaining S O3 is decomposed by a 

 secondary action. 



We are thus able to represent equally well the increased facility of 

 decomposition of water, either by the addition of an acid or of an 

 alkali, (in the latter case secondary action may, however, take place,) 

 and this, too, from a purely chemical point of view, chosen without 

 reference to electrolytic action. 



One further remark is required. In the salt type N 11, is capable 

 of takin -2; the place of a metal ; this is simply a statement of the fact, 

 but in electrolysis this substitution for the metallic element is with- 

 drawn instead of the metals but not being capable of an independent 

 existence, (under the circumstances, if at all,) it appears in the form 

 of hydrogen and ammonia N H3 + H. We do not pretend to follow 

 out the cases in which one or more of the equivalents of the hydrogen 

 of the N H, are replaced by some other elements which experience has 

 shown can be introduced instead of them. The mode of reasoning 

 and the consequences will be similar. 



It will not be difficult, by carrying out the same theory of the com- 

 position of salts to explain the electrolysis of the phosphates and 

 arseniates, noticed in a subsequent part of this report. 



Daniell's views, then, are correct, as far as they go, in showing the 

 manner in which salts are broken up in eleltrolysis, but they are in 

 error in considering that the two parts into which the salt is broken 

 are two distinct substances which are capable of independent existence. 

 Hence the failure of Daniell in his attempts to isolate his " Oxysul- 

 phion," S 0^, a compound incapable of independent existence. 



The difference between these two theories of the constitution of 

 salts, beyond the im})ortant fact that one is far more general than the 

 other, may by some be considered as trivial ; but this is not the case, 

 for at least one valuable result is obtained, that chemists are relieved 

 from the opprobrium of describing and descanting upon the important 

 properties of certain compounds which tliey cannot produce and which 

 the most intelligent among them do not deem capable of production 

 or of independent existence. 



In commencing this note the intention was simply to announce that 

 the hypothesis of Daniell, as to the constitution of salts, was not in 

 accordance with the commonly received opinion of chemists of the 

 present day, and to follow out the latter, with reference to the phe- 

 nomena of electrolysis, to what were deemed their inevitable results. 

 But, upon examination, it does not appear that any formal announce- 

 ment of the concordance of the present views of chemists with the laws 

 of electrolysis has been made, though doubtless every intelligent man 

 has followed up this concordance, for it is inevitable. This reflects 

 greater credit upon those who have, in a more advanced state of the 

 science, announced correct purely chemical theories, and upon Davy, 

 who, at a much earlier period, gave the hint of, possibly, a far higher 

 generalization, while still much credit is due to Daniell for leading 

 back the scientific world to sounder views. — Gr. C. S.] 



§ 172. Deposits upon diaphragms. — In the memoir just discussed 

 Daniell also describes some very interesting phenomena, the considera- 



