METALLURGY. 253 



processes in which metals are extracted from their ores. Most 

 ores require to be fluxed in contact with charcoal, or some other 

 substance containing phlogiston, before they will yield their 

 metals; and when they are thus fluxed, the metal, instead of 

 being dispersed in vapour, is collected into a mass at the bottom 

 of the vessel, or furnace, in which the operation is performed. 

 Calamine, in like manner, must be united to phlogiston, before 

 its metallic part, which is called zinc, will be properly formed ; 

 but as soon as it is formed, it flies off in vapour, and taking fire, 

 burns with a vivid flame. This phenomenon is easily made appa- 

 rent, by mixing calamine in powder and charcoal dust together, and 

 exposing the mixture to a melting heat ; for a flame will issue from 

 it very different from what charcoal alone would yield : no mass 

 of any metallic substance will be found at the bottom of the vessel ; 

 but in tht place where the experiment is made, there will be seen 

 many white flocks floating in the air: these flocks are the ashes of 

 the metallic substance of the calamine j they are called flowers 

 of zinc, lana philosophorum, nihil album, and by other fanciful 

 names. The metallic vapour which rises from a mixture of cala. 

 mine and charcoal, when exposed to a proper degree of heat, and 

 the firing of which causes the flame which may be observed, can. 

 not burn without air; and it was on this principle that Marggraf 

 proceeded, when he extracted zinc from calamine by distillation in 

 close vessels in 1746. He put eight parts of powdered calamine, 

 and one of powdered charcoal, well mixed together, into an ear- 

 then retort ; and having fitted a receiver, with a little water in it, 

 to the m-rk of the retort, in such a manner as to exclude the air, 

 he exposed the mixture to a strong heat; there rose into the neck 

 of the retort, where it was condensed, the metallic vapour of the 

 calamine. By this method he ascertained the quantity of zinc 

 contained in different sorts of calamine. 



Parts. Parts. 



Calamine from near Cracow 16 gave 2{ of zinc. 



from England 16 3 



from Breslaw 16 4% 



from Hungary 16 



from Holywell in Flintshire 16 



He tried some stones from Aix.Ia-Chapelle, which had been given 

 him for calamine, in the same way, but obtained no zinc from 



