METALLURGY. 2fll 



union forms a metallic substance, which penetrates the copper 

 contiguous to it, changing its colour from red to yellow, and aug 

 menting its weight in a great proportion. The greater the surface of 

 a definitive weight of copper, the more space has the metallic vapour 

 of the calamine to attach itself to ; and (his is the reason that the cop. 

 per is granulated, and that it is kept from melting and running 

 into a mass at the bottom of the vessel, till near the end of the 

 operation, when the heat is increased for that purpose. 



The German brass-makers, in the time of Erckern, used to mix 

 sixty. four pounds of small pieces of copper with forty- six pounds 

 of calamine and charcoal, and from this mixture they generally 

 obtained pounds of brass*. Cramer recommends three parts 

 of powdered calamine to be mixed with an equal weight of charcoal 

 dust and two parts of copper, and says that the brass obtained by 

 the process exceeds the weight of copper by a fourth, or even a 

 third part of its weight t. At most of our English brass-works 

 they use forty. five pounds of copper to sixty pounds of calamine 

 for making ingot brass, and they seldom obtain less than sixty, or 

 more than seventy, pounds of brass ; at Holywell they reckoned 

 the medium product to be sixty.eight : and heure a ton of copper 

 by this operation, becomes rather more than a ton and a half of 

 brass. This is a larger increase of weight in the copper than is 

 observed in any of the foreign manufactories that I have ever read 

 of; and it may be attributed to two causes to the superior excel, 

 lence of our calamine, and to our using granulated copper. Pos- 

 tlethwayte, in his Commercial Dictionary, attributes the difference 

 in the increase of weight acquired by the brass to the different na- 

 tures of the coppers which are used : " There is an increase of 

 forty.eight or fifty pounds in an hundred, if copper of Hungary 

 or Sweden be used; that of Norway yields but thirty .fight, and 

 that of Italy but twenty," When they make brass which is to be 

 cast into plates, from which pans and kettles are to be made, and 

 wire is to be drawn, they use calaminf of the finest sort, and in 

 a greater proportion than when common brass is made generally 

 fifty six pounds of calamine to thirty-four of copper. Old brass 

 which has been frequently exposed to the action of fire, when mix. 

 ed with the copper and calamine in the making of brass, renders 



Flet* minor, by Sir J. Pettys. j. 286. Newman gives the tame proportion, 

 p. 65. 

 fCram. An Doc. Vol. II. p. 246. 



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