260 METALLURGY. 



made by Mr. Emerson is whiter and brighter than any other either 

 English or foreign zinc ; but I do not know that it owes these qua. 

 litits to its being purified by sulphur. Zinc and copper, when 

 melt< (I to^rthi r in different proportions, constitute what are called 

 pinchbecks, &c. of different yellow colours. Marggraf melted 

 pure zinc and pure copper together, in a great variety of propor- 

 tions, and he found that eleven, or even twelve parts of copper 

 being mixed with one part of zinc (by putting the zinc into the cop. 

 per when melted) gave a most beautiful and very malleable tombac 

 or pinchbeck*. Mr. Baunie gives the following process for mak- 

 ing a metal, which he says is called Or dc Manltcim, and which 

 is used for imitating gold in a variety of toys, and also on lace. 

 Melt an ounce and a half of copper, add to it three drams of zinc, 

 cover instantly the mixture with charcoal dust to prevent the cal- 

 cination of the zinc +. This covering the melted mass with char, 

 coal is certainly serviceable in the way the author mentions ; and 

 it is on a similar principle, that when they melt steel at Sheffield 

 they keep the surface of it covered with charcoal ; but I think it 

 probable also, that the charcoal contributes to exalt the golden 

 colour of the pinchbeck. These yellow metals are seldom so mal- 

 leable as brass, on account of the zinc which is used in making 

 them not being in so pure a state, as that is which is combined with 

 copper when brass is made; yet it appears from the experiments 

 of Marggraf and Baume before mentioned, that when pure zinc 

 and pure copper are used in proper proportions, very malleable 

 brass may be made thereby. Mr. Emerson has a patent for mak- 

 ing brass with zinc and copper, as I have been informed ; and his 

 brass is said to be more malleable ; more beautiful, and of a colour 

 more resembling gold than ordinary brass is. It is quite free from 

 knots or hard places, arising from iron, to which other brass is sub- 

 ject ; and this quality, as it respects the magnetic needle, renders 

 it of great importance in making compasses. The method of mak- 

 ing ordinary brass I will now describe. 



Copper in thin plates, or which is better, copper reduced (by 

 being poured, when melted, into water) into grains of the size of 

 large shot, is mixed with calamine and charcoal, both in powder, 

 and exposed in a melting pot for several hours to a fire not quite 

 itrong enough to melt the copper, but sufficient for uniting the 

 metallic earth of the calamine to the phlogiston of the coal ; this 



Mem. of Berlin, 1774. t Chy . par M, Bawoc, Vol. 11, p. 662. 



