RECENT PROGRESS IN PHYSICS. 377 



I of it is conducted by the water, and I by the hydrate of sulphuric 

 acid, and thus we obtain : 



At the positive pole — At the negative pole — 



f equiv. 0, f equiv. H, 



^ equiv. SO^, I equiv. H, 



and by the decomposition of SO^ : 



At the positive pole — At the negative pole — 



f equiv. 0, f equiv. H, 



I equiv. SO3 + {- equiv. 0, ^ equiv. H, 



I equiv. SO, -{- 1 equiv. 0, . ' 1 equiv. H, 



exactly as demonstrated by the experiment. 



In support of his view of the electrolysis of acid salts Daniell also 

 mentions the fact, that from a neutral solution of sulphate of copper 

 the metal is deposited in a compact mass at the negative pole, and 

 firmly adheres to it ; while the copper is deposited in a more pulveru- 

 lent state when reduced from a strongly acid solution. 



In the neutral solution only SOjCu. is decomposed, and therefore 

 only Cu. deposited at the platinode; while in an acid solution HO and 

 SO4H are also electrolized, and, therefore, besides Cu., H is also libe- 

 rated at the negative pole. 



Daniell also relates some additional observations on the electrolysis 

 of secondary combinations. He examined carbonate ofpotassa, of soda, 

 and of ammonia, and found that the carbonic acid and oxygen, both 

 given off as gas at the positive pole, were equivalent to the alkali and 

 hydrogen at the negative pole. He considers, therefore, the carbo- 

 nates as oxycarbonions of potassium, sodium, ammonium, &c. 



Note. — [Daniell' s theory of the constitution of salts, although 

 affording, as far as it goes, a simple explanation of the phenomena 

 of electrolysis, is not adopted by chemists at the present time. The 

 theory now becoming general is one which, while it is perfectly in 

 accordance with the whole range of chemical facts, explains, as well 

 as that of Daniell's, everything relating to electrolysis, but is sus- 

 ceptible of far greater extension. In this view salts are considered 

 not as made up of two pre-existing substances, but as a ivhole, a form 

 or type dependent upon laws of nature which we can yet but partly 

 determine. The general expression for a salt will then be E. M., or, 

 rather, R. Mn., in which M. represents a metal, or hydrogen, (a metal,) 

 which may be replaced by any other metal. li, in this case, repre- 

 sents that element, or those elements, which combine with a metal or 

 metals so replaceable. This view is only an extension of that of Davy, 

 which, by a splendid generalization, includes the so-called haloid 

 salts — the chlorides, iodides, &c. — under a common head with the 

 salts of, what are called, oxygen acids. A departure from this view 

 at one time led to the separation of common salt (chloride of sodium) 

 from the very family to which it gave name, and involved an intricate 

 and circuitous explanation of phenomena which were evidently iden- 

 tical. 



But the theory of the constitution of salts to which we refer not 



