FRAUDULENT GOLD. 67 



phimc acid, and triturate the resulting paste of sulphate ^^'it]l 

 pure, finely-divided copper, diffused in water at 140°-158°. 

 There must be sufficient copper to form a composition of 70 

 pts. mercury and 30 pts. copper, or enough to reduce all the 

 mercury salt employed, and to alloy the mercury eliminated. 

 After rubbing for some time, the amalgam is to be well 

 washed, pressed in a leather bag, and formed into small cakes 

 for use. 



Various Alloys. — Stirling forms an alloy of zinc and iron, 

 by throwing a quantity of zinc into a cupola after the metal is 

 run out and the blast stopped, whereby an alloy is formed with 

 the iron still adhering to the sides, fuel, &:c. When the alloy 

 contains more than 7 per cent, iron, zinc is to be added to it ; 

 when less than 4 per cent., iron is to be added, the best alloy 

 containing from 4 to 7 per cent. iron. This alloy is used for 

 other alloys instead of zinc. An alloy of copper and man- 

 ganese is made by adding to melted copper from J to 2 per 

 cent, of black oxide of manganese, or by mixing them before- 

 hand and then melting, keeping the metal in either case 

 covered with a reducing flux. A gold-colored alloy is pro- 

 duced by adding 1 pt. of the zinc alloy to 4 pts. of the copper 

 alloy : it is very malleable and ductile, and takes a fine polish. 

 The addition of | per cent of tin hardens the gold alloy, al- 

 though as much as 4 per cent, may be used. To prevent 

 heating by friction, lead may be added to the alloy. An 

 improved German silver is made by melting 10 pts. copper, 

 2 pts. nickel, and 6 pts. of the iron-zinc alloy ; or 8 pts. cop- 

 per, 2 pts. nickel, and 4 pts. of the iron-zinc alloy. A much 

 larger proportion of iron-zinc renders the metal too hard for 

 rolling, but good for some casting. An excess of copper 

 spoils the color. The nickel and copper are first melted and 

 the zinc alloy then introduced under cover of a reducing 

 flux. (Rep. Pat. Inv. July, 1850.) 



Fraudulent Gold. — When gold of 12 carats or less, is al- 

 loyed with zinc instead of silver, it still retains a true golden 

 color, and this property has caused its extensive use in the 

 manufacture of fraudulent jewelry. (Technologiste, 1847.) 



