CHEMICAL SCIENCE. 237 



anode of the required alloy. These solutions are subject to the same 

 treatment and control as those of the brass. 



COATING IRON WITH ZINC AND OTHER METALS. 



Messrs. Gressel and Redwood, of London, recently patented the 

 following method of coating iron with zinc and other metals. 



To Coat Iron with Zinc. The zinc is melted in an open vessel, and 

 on its surface is placed a layer of the chloride of zinc, or a mixture of 

 equal parts of chloride of zinc and chloride of potassium, in the pro- 

 portion of eight of the former and two of the latter. When the salt 

 is in a state of fusion, the metal to be coated is placed in the bath, and 

 allowed to remain there till a coating of sufficient thickness has been 

 obtained ; it is then withdrawn, and any parts of its surface imper- 

 fectly covered are sprinkled with sal ammoniac, and the sheet of iron 

 again immersed in the bath. 



To coat Iron with Silver. The metal must be first amalgamated 

 with mercury by the following process : 12 parts of mercury, 1 of zinc, 

 2 of sulphate of iron, 2 of muriatic acid, and 12 of water are mixed 

 together, and heated in an open vessel to about 200 Fah. ; the iron is 

 then immersed, and the mercury rubbed on its surface until amalga- 

 mation is effected. The silver or allov is to be melted in a crucible. 







and the amalgamated iron placed therein, when a coating of silver or 

 alloy will be deposited. 



To coat Iron with Copper or Brass. The copper or other coating 

 is to be melted in a suitable vessel, and a stratum of borosiiicate of 

 lead placed on its surface ; the iron is then to be plunged into the 

 molten metal, and retained there until a coating is deposited on it. 

 Iron coated with the tin or lead may be treated in a similar manner. 

 Another method of coating iron with copper is to place in a crucible 

 a quantity of chloride of copper, upon which is laid the iron to be 

 coated, and over that a quantity of charcoal. The crucible is then 

 submitted to a red heat and the chloride of copper fused, and a coat- 

 ing of copper deposited on the iron ; or the. vapor of chloride of 

 copper may be employed for the same purpose. The coating of cop- 

 per thus obtained, may be converted to one of brass by exposing the 

 sheet of metal to the vapor of zinc in a closed vessel. 



DESILVERING OF LEAD. 



A patent has recently been taken out by Mr. Parks, of England, for 

 a process by which he separates silver from argentiferous lead ores 

 entirely by one operation. To do this, the alloy of silver and lead 

 is melted in the usual way in a large iron pot. To this a small quan- 

 tity, a few pounds of zinc per ton, is added, the whole mixed up and 

 allowed to remain a short time. By this means the silver is brought to 

 the surface in the form of alloy with zinc, and this mixture is subse- 

 quently skimmed off and treated for the silver it contains. In order 

 to do this the zinc is first partially separated by oxydation and the 

 residual alloys afterwards treated in the cupel. 



