﻿42 Mr. W. H. Walenn on Solutions for depositing 



and the zinc solution was allowed to infiltrate considerably into 

 the external cupric solution ; the result was that the botryoidal 

 form entirely disappeared, the metal being deposited in tufts 

 close together (when viewed by the naked eye) and rising verti- 

 cally from the surface of the cathode. These, when viewed with 

 a microscope, were seen to be perfectly separate tufts standing 

 up at right angles to the surface. The influence of a small pro- 

 portion of zincic sulphate to the gallon of depositing solution, 

 as recommended by Napier* (one ounce to the pound of ^cupric 

 sulphate), is known to nearly annul the botryoidal form, and to 

 render the deposit tough, compact, and even ; but, to test the 

 action of an excess of this salt, a solution was made as follows: — 



2. Abnormal solution.— Cupric sulphate, one pound; sulphuric 

 acid, one pound; zincic sulphate, four ounces; water, one gallon. 



On trial with a Maynooth cell, this solution yielded a result 

 like in character to that produced by the infiltration of the zinc 

 solution from the porous cell, but more marked. 



The general characteristic of electrobrassing-solutions, when 

 in good order, is to deposit the metal in needles at right angles 

 to the surface, more or less detached from one another, accord- 

 ing to the state of the solution and the electric power employed. 

 This peculiarity can be traced to the fact of alkaline solutions 

 being used for this purpose, the metal of the alkali being prone 

 to be deposited (for an infinitely small duration of time) toge- 

 ther with the heavy metals, and to the hydrogen copiously given 

 off during deposition. With Morris and Johnson's solution f 

 (the solvent solution of which is composed of potassic cyanide 

 and ammonic sesquicarbonate) it was found impossible to deposit 

 a thickness of metal of more than *01 inch free from spongy or 

 tree-like formation. Other solutions were found to give a like 

 result. Although in facility of management and constancy of 

 action the author found that a solvent solution composed of po- 

 tassic cyanide and neutral ammonic tartrate J was superior to 

 the other known brass solutions, this solution would not deposit 

 good metal of more than *03 inch thick, hydrogen being given 

 off (in less quantity than in other solutions) during deposition. 



Having observed that a solution containing the sulphates of 

 the metals, together with potassic cyanide and an excess of am- 

 monia > could be worked with a single- cell arrangement (the 

 porous cell containing the same materials as the external cell 

 without the copper and zinc) without the evolution of hydrogen, 

 the author found that this was owing to the presence of the oxides 

 of the metals, as well as their cyanides, in the solution ; and, 



* Electro-metallurgy. By James Napier, F.C.S. Fourth edition, p. 49. 

 t Morris and Johnson's Patent- Specification, No. 1032, a. d. 1852. 

 X Walenn's Patent-Specification, No. 1540, a.d. 1857. 



