£92 1XPERIMENTJ ON VAfclOUS ALLOYS OP GOLD. 



To 476 grains of fine malleable copper, in fufion, four 

 grains of antimony were added, and, being well mixed, the 

 whole was poured into a mould. 



The colour of this copper, when filed and poliftied, was 

 fuch as not eafily to be diftinguifhed from that which had not 

 been thus alloyed. 



It wasalfo hammered and rolled, without (hewing any figns 

 of brittlenefs. The fpecific gravity was 8,354 *. 



The like quantity of copper was alloyed with four grains of 

 lead. 



This alfo was ductile, and did not fufFer any apparent 

 change of colour. 



The fpecific gravity was 8,472. 



The fame experiment was repeated with four grains of bif- 

 muth ; but the copper thus alloyed was exceedingly fpongy 

 and brittle. 



It appears, therefore, that four grains of antimony, or of 

 lead, may be prefent in one ounce, or 480 grains of copper, 

 without producing any very apparent change in colour or 

 ductility, and but little in fpecific gravity ; fuch copper may, 

 therefore, without fufpicion, be occafionally employed to alloy- 

 gold; then, however, the antimony or lead will produce a 

 powerful effect ; for it has been proved, that -j-^Ve of either of 

 thefe will deftroy the duclility of gold. But, fuppofing one 

 ounce troy of copper which contains four grains of antimony, 

 or of lead, to be employed to alloy eleven ounces of gold, 

 24 carats fine, there would then be four grains of the above- 

 mentioned metals in the 12 ounces or troy pound ; and there- 

 fore the quantity of thefe would be confiderably more than is 

 required to deftroy the ductility of gold. For the troy pound 

 contains 5760 grains; and 4 is to 5760 as 1 to 1440; con- 

 sequently, this proportion much exceeds the quantity which is 

 capable of producing the above-mentioned effect, 

 It often contains g u t the copper of commerce often contains a much greater 

 ablcproportion." proportion of one or other of thefe metals ; and, although it 

 then appears more pale than common, yet it has, without 

 fufpicion, been purchafed by thofe who, from their profeflion, 

 are fuppofed to be competent judges, and who efpecially 



* The fineft Swedifli copper was employed in thefe experiments j 

 the fpecific gravity of it was 8,895. 



2 require 



