82 HYDROMETALLUKGY. [ill. 



For coppering larger vessels, the cyanide solutions are too 

 expensive, and blue vitriol solution, acidulated with sulphuric 

 acid, will be all-sufficient. — Eisner. 



Antique Bronze, or Patina. — The following composition is 

 said to produce the effect rapidly. 1 pt. salammoniac, 3 pts. 

 powdered argal, and 3 pts. common salt, are dissolved in 12 

 pts. hot water, and 8 pts. of a solution of nitrate of copper 

 added. (The strength of this solution is not given. — Eisner.) 

 Newly made articles of bronze are coated several times with 

 the above solution. A larger proportion of common salt gives 

 a yellowish, and less gives a more bluish tint. (Polytech. 

 Notizbl. 1846.) 



C. Ploffmann produces a beautiful chrome-green brown, by 

 first touching (not brushing) the surface of the bronze with a 

 very dilute solution of nitrate of copper, containing a little 

 common salt, brushing it off, then touching it with a solution 

 of 1 pt. binoxalate of potassa, 4|- pts. salammoniac, and 94|- 

 pts. vinegar, and again brushing it off. This operation is 

 repeated several times. In the course of a week, the article 

 has a greenish-brown hue, with a bluish-green tone in the 

 depressions, and withstands the weather. 



Elsraer proposed a method, some years since, which produced 

 an antique, almost identical with that produced naturally, on 

 bronzes. The bronze article, with a clean surface, was dipped 

 into dilute vinegar, and exposed for several weeks to a moist 

 atmosphere of carbonic acid. The operation is economical, 

 and easily executed. (Berlin. Gewerbe-Industrie u. Handelsbl. 

 xii. 78.) 



Bronzing and Brassing. — Brunnel, Bisson, and Gaugain, 

 have given (Newton's Journ. 1848) a new process for brassing 

 articles of iron, steel, lead, zinc, and their alloys with each 

 other and with bismuth and antimony, by means of the follow- 

 ing bath : 500 pts. carbonate of potassa, 20 pts. chloride of 

 copper, 40 pts. sulphate of zinc, 250 pts. nitrate of ammonia. 

 For bronzing, the zinc-salt is to be replaced by one of tin. 

 The object to be plated, after being brightened by scouring, 

 is connected with the negative pole of a Bunsen battery ; — a 



