160 



Abfolute prccl- 

 fion not to be 

 expedted. 



Specific gravity 

 of ftandard gold 

 of different 

 kinds. 

 That of our 

 ftandard gold 

 muft occafion- 

 ally differ. 



EXPERIMENTS ON VARIOUS ALLOYS OF GOLD. 



3. The unequal diftribution of the metal, or metals, employed 

 as an alloy, throughout the mafs intended to be alloyed. 



4. The peculiar effeds which certain metals produce, when 

 ufed fingly or conjointly as alloys, and which are very different 

 from the refults of calculation.* 



5. Heat, whether produced by fridion or excited in any other 

 manner. 



As, therefore, the fpecific gravity of metals is liable to be in- 

 fluenced by fuch a variety of caufes, it is almoft in vain to expe6t 

 abfolute precifion in the refults of experiments made by different 

 perfons ; but, at the fame time, it may be obferved, that by 

 proper care and attention to the above circumftances, a degree 

 of accuracy may be attained, fufficient to anfwer almofl every 

 ufeful purpofe, although, from what has been faid, it mufl 

 appear improper to form opinions upon fmall fractional varia- 

 tions. By the experiments which were made, with every poffible 

 precaution, upon feparate and intire ingots of gold, reduced to 

 ftandard by filver, by filverand copper, and by copper alone, 

 when cafl in an iron mould like a cupel, it appeared, that the 

 fpecific gravity of each of thefe kinds of ftandard gold is as 

 follows. 



Gold made ftandard by filver - - - - 17,927 

 Gold made ftandard by filver and copper - 17,3 l-l- 



Gold made ftandard by copper - - - - 17,157. 

 Now, as our gold coin commonly contains filver as part of the 

 alloy, and as at different times this proportion of filver muft have 

 been various, and even contiderable, particularly when the gold 

 of Portugal, which is alloyed with filver, was brought to the 

 Mint, it naturally follows that, exclufive of the many other 

 caufes of variation which have lately been enumerated, the fpe- 

 cific gravity of our ftandard gold muft occaiionally be different, 



* There can be no doubt but that the effefts of compound alloys 

 are, in general, very different from thofe of each metal feparately 

 confidered; and that fuch metallic combinations or compound al- 

 loys, like neutral falts, and many other compounds, have peculiar 

 properties, which aft varioufly upon the metals to which thefe com- 

 pound alloys are added. A great number of accurate experiment! 

 are, however, requifite to elucidate a queftion lb intricate. 



It may here be alfo obferved, that the peculiar properties of com- 

 pound alloys, prove them to be real chemical combinations. C. H. 



according 



