274 COMBINATION OF MERCURY 



mercury which ib obtained by dift illation from 

 white precipitated mercury, with a mixture of 

 iron filings, or fixed alkali. But I cannot think 

 this to poilefs any higher virtues than other pure 

 quick ill vet. Cold that has contracted an unna- 

 tural hardnefs and brittlenefs, by intermixture 

 with other metals, or by tlie action of their va- 

 pour, recovers its natural ductility, it" it be melt- 

 ed, and a quantity of corrofivc fublimate cafl 

 upon it ; for the marine acid having a greater 

 affinity with mod of the other metals than with 

 quickfilver or gold, fortiikcs the quickiilver with 

 which it was united in the corrolive fublimate, 

 and attracts them from the gold. In this pro- 

 cefs care mufl be taken, that the operator iuf- 

 fer no inconvenience from the vapours which a- 

 rife from the corrolive fublimate diilblved by the 

 heat of the fire, the pure mercury, and the ex- 

 traneous metals Separated from the gold. 



This mode of .purifying gold is preferable to 

 the pvoceis by deflagration with nitre ; f<*r the 

 deflagration of the nitre ieparates riot only the 

 bafer metals, but even lilver from gold. It is of 

 importance to obferve, that corrolive fublimate 

 may be employed to prefcrvc metals that are 

 mixed and fufed with zinc, from contracting any 

 undue rigidity. Upon this principle, according 

 to Neuman, workers in brafs throw fait on the 

 metal in fulion, to render it fofter and more duc- 

 tile. 



Corrofivc 



