On the Structure of Electro-precipitated Metals. ^-^^ ^XTj'^'''''* ♦ 



we suppose a velocity equal and opposite to that of the aetttie^' '^ '**' 

 to be impressed, both on the aether and on the bodies of the 

 solar system, the case is reduced to that of the solar system 

 moving through the aether supposed to be at rest. 



IV. On the Structure of Electro-precipitated Metals. 

 By Warren De la Rue, Esq.^- 



'^r^HE following observations, being the result of an exten- 

 -*• sive series of experiments on the practical application of the 

 processes of electro-metallurgy, will, I am induced to believe, 

 be acceptable to the Chemical Society. 



The various appearances of the metallic deposit are fami- 

 liar to all manipulators in electro-metallurgy, and are distin- 

 guished by the names crystalline, lesser crystalline, malleable, 

 sandy and spongy ; the latter being produced by an excess of 

 power in the battery, the first by too small a power in rela- 

 tion to the strength of the solution operated on. All these 

 deposits are however merely modifications of each other, they 

 are essentially crystalline, and even the malleable, or in other 

 words the most cohesive, is very inferior in strength to metals 

 wrought by the processes in ordinary use. 



The malleable is that deposit usually required ; yet, even 

 with all the art of a practised electro metallurgist, it is diffi- 

 cult for a lengthened period to obtain it, inasmuch as the 

 power of the battery, the temperature of the air, and conse- 

 quently the conducting power of the fluids composing the 

 circuit are constantly changing their relation to the strength 

 of the electrolyte to be decomposed. There are other causes 

 presently to be considered which also play an important part 

 in producing these difficulties, and which we shall better 

 understand by considering what effect the form of the matrix 

 and the nature of its original surface have on the resulting 

 precipitate. 



It is well known to persons conversant with the precipita- 

 tion of metals from their respective solutions by means of 

 voltaic electricity, that these solutions become exhausted of 

 the metal at the cathode to such an extent, that if we place 

 the cathode on the surfiice of the liquid all action after a short 

 time ceases : the exhausted liquid being specifically lighter, no 

 mechanical transfer of fresh liquid takes placet, ^"'^^ conse- 



* Communicated by the Chemical Society; having been read Febi-iiary 

 17, 1845. 



t Professor Daniell and Dr. Miller, in a paper on the electrolysis of se- 

 condary compounds, have entered into the investigation of these phaeno- 

 niena. 



