1 76 Prof. Daniell and Dr. Miller on the 



established. First. When aqueous solutions of the neutral 

 metallic salts are exposed to the action of the voltaic current, 

 they are invariably decomposed. When the metal is one of 

 that class which does not decompose water at ordinary tem- 

 peratures, it is precipitated in the metallic state at the plati- 

 node : when it is of the class which does decompose water, its 

 oxide, with an equivalent proportion of hydrogen, appears at 

 the same electrode. The acid at the same time is set free at 

 the zincode, accompanied by an equivalent proportion of oxy- 

 gen. Second. When these results are compared with those of 

 an independent voltameter in the same circuit, it is found that 

 a certain proportion of the force which resolves a single equi- 

 valent of a simple* electrolyte into its anion and cation, pro- 

 duces the resolution of a full equivalent of the complex electro- 

 lyte into a simple metallic cation and a compound anion. 

 Third. When aqueous solutions of ammoniacal salts are elec- 

 trolysed, similar results are obtained ; but instead of a simple 

 metal being disengaged at the platinode, an equivalent of am- 

 monia, accompanied in all cases by an equivalent of hydrogen, 

 appears at the platinode. Fourth. We are thus entitled to 

 conclude that in the electrolysis of complex electrolytes, dif^ 

 ferent elements travel together under the influence of the vol- 

 taic current as compound anions and cations, or as iso-electric 

 bodies; that is, groups which are equivalent to each other, 

 and to simple ions, in their relations to the electric forces. 



One of the most interesting results of this investigation, was 

 the independent confirmation which it afforded of two cele- 

 brated hypotheses, viz. that of Davy regarding the constitu- 

 tion of aqueo-acids, and the general analogy in the constitu- 

 tion of salts, whether derived from oxyacids or hydro-acids ; 

 and that of Berzelius concerning the constitution of ammo- 

 nium. 



It was with a view to extend our knowledge of such iso- 

 electric groups, and to trace their connexion with chemical 

 radicles, that we commenced our experiments. 



Before we enter upon their detail, it will be best to make a 

 few remarks upon the mode of measuring their results, which 

 has been adopted. It is founded upon the undoubted law of 

 definite electric action ; and we have indifferently taken the 

 amount of the ions disengaged at either or both the electrodes 

 by the primary action of the current, or the secondary action 

 of the elements. But there is another mode of effecting this 

 purpose, by a diaphragm cell, in which the products of elec- 

 trolysis may be kept separate ; a method founded upon the 



* By a simple electrolyte is meant one containing only two elementary 

 substances, being the simplest form of matter capable of electrolysis. 



