EXPERIMENTS ON VARIOUS ALLOYS OP GOLD. 239 



GOLD ALLOYBD WITH COBALT. 



Experiment I. to IV. 

 This addition debafed the colour of the gold, and rendered GoId *nd cobalt, 

 ft brittle. When to an alloy of about 10 parts gold, and 1 

 part copper, nearly half a quarter part of cobalt were added, 

 the metal began to be ductile. 



GOLD ALLOYED WITH NICKEL. 



Experiment I. to IV. 

 The colour and dudility of gold were injured by nickel, Gold and *Ml 

 but lefs than by any other of the brittle metals. When to 

 about eleven parts of gold, and one of copper, one fourth 

 of a part of nickel was added, the compound was fcarcely 

 brittle. 



GOLD ALLOYED WITH MANGANESE. 



Experiment I. to III. 

 The black oxide of manganefe ftrongly heated with gold GoM * n(1 roan- 

 did not affect it. But when olive oil had been previoufly 

 burned on the oxide, this powder ftrongly and permanently 

 heated with gold, rendered it pale and brittle. This alloy is 

 lefs fulible than pure gold ; it does not change by long ex- 

 pofure to the air; and the manganefe is defended from the 

 ufual action of acids. It may be leparated by cupellation, or 

 better by quartation and nitric acid. 



GOLD ALLOYED WITH BISMUTH. 



Experiment I. to VI. 

 Bifmuth added to pure, or to alloyed gold, is exceedingly Gold and bif- 

 injurious to its colour and ductility. It produces thefe effects m 

 when the quantity is no more than -^Vs part of the mafs; and 

 the combination takes place by the vapor of bifmuth, in open 

 as well as clofe veffels. 



GOLD ALLOYED WITH LE AD. 



Experiment I. to IX. 



Lead is nearly as injurious to gold as bifmuth ; one quarter Gold and lead, 

 of a grain in the ounce producing complete brittlenefs. Its 

 vapor in clofe veffels greatly contaminates gold, but in open 

 veffels the effect was inconfiderable. 



Vol. VI. — August, U goljb 



