﻿On Solutions for Electrodeposition of Copper and Brass. 41 



bisulphide of carbon, the danger of an explosion in the case of 

 fire is eliminated; for if the liquid happen to be ignited by 

 some cause or other, the gun-cotton will be only slowly destroyed. 

 When required for use, a brief exposure to air restores its ex- 

 plosive properties. 



The Hague, December 1870. 



VII. On Solutions for depositing Copper and Brass by means of 

 Electric Force. By W. H. Walenn, F.C.S.* 



THE practical value of an electro-deposit mainly depends 

 upon its structure. As this structure is formed under 

 circumstances that have no analogy in the ordinary treatment 

 of metals by heat, it is worthy of separate study. When a 

 metal is cast into the desired form, the homogeneousness of 

 the result is, to a great extent, ensured by the whole of the metal 

 being in the same state at the same time ; the electro-deposit, 

 on the contrary, takes time, and frequently has to bear the in- 

 fluence of fluctuating electric power in its production, besides 

 other irregularities that none can realize except those who have 

 studied them and have submitted the resulting deposit to rigo- 

 rous examination. 



The variety of structure of deposits of metals and alloys from 

 their electrolytical solutions is very great, and is sometimes 

 much affected by slight alterations and impurities in the solu- 

 tion, to an extent not generally known. To obtain trustworthy 

 results in the examination of deposits, it is necessary to observe 

 minutely the surface of the metal as soon as it comes from the 

 solution, as well as the fracture of the deposit, with a compara- 

 tively low magnifying-power, a single lens being sufficient. 



The deposits from the solution of a neutral salt of a metal, or 

 of a neutral salt with an excess of its acid radical, are well known, 

 and may be classified into the " powdery " (great electric power 

 upon a weak solution giving a black powder with the principal 

 metals), the "reguline," and the "crystalline." The reguline 

 deposit is subject to variation in quality ; in the case of copper, 

 perhaps the best solution to deposit the normal quality is : — 



1. Normal solution. — Cupric sulphate, one pound; sulphuric 

 acid, one pound ; water, one gallon. 



This solution deposits the metal in a compact mass, quite 

 solid, and having an exterior surface somewhat botryoidal in 

 character. 



On one occasion the normal solution was worked by means of 

 a porous cell without a separate battery (the single-cell process), 



* Communicated by the Author. 



