184/.] On the Re/mage of under standard Stive?. o&? 



present Assay blaster, I have been enabled to convince myself that in 

 skilful and conscientious hands this method ensures all the accuracy 

 which is required in the operations of the mint and for commercial 

 purposes. Its range of error will not exceed 2 parts in 1000, and be 

 still within the deviation permitted by the law with reference to the 

 impossibility of ensuring an exact mathematical alloy in all minting 

 operations. But this system of assay demands the appliance of so 

 much skill and such cumbrous apparatus that to the experimentalist 

 " in the jungle" it affords no resource. 



The French method, by solution in nitric acid and precipitation of 

 the silver as chloride by common salt, is only applicable where the 

 silver under assay is alloyed with copper only. If it contain lead, 

 mercury, tin or iron, the results are fallacious. I enter upon no details, 

 as I am not addressing these remarks to assay ers. It is enough to 

 say that the solution becomes so milky from the presence of chloride 

 of lead, calomel, or peroxide of tin, that it is impossible to see and note 

 correctly when the proper quantity of the salt test-liquor has been added ; 

 or on the other hand, if the experimentalist desires to weigh the preci- 

 pitate, he is liable to be deceived by the quantity of insoluble chlorides 

 of base metals united with that of silver. 



I pass therefore to another and a ready resource, which only requires 

 a Florence flask or two and a little nitric acid for its performance, and 

 by which the experimentalist may proceed as follows : — 



Weigh 24 grains of the silver to be examined, and dissolve it by 

 means of one fluid drachm of pure nitric acid, about sp. gr. 1350, and 

 half an ounce (fluid) of rain or distilled water. When dissolved dilute the 

 fluid to two ounces with distilled water and introduce a clean slip of 

 pure copper. Boil the contents of the flask over a lamp or on a pan 

 of sand over a charcoal fire, so long as silver is deposited on the 

 copper, and until a fresh slip of copper introduced is not tarnished — 

 then let the liquid settle, decant the blue liquid, replace with water, 

 decant once more, placing the thumb on the mouth of the flask 

 invert it and let the silver escape upon a small China saucer — let the 

 moisture drain off and dry the silver thoroughly over the hot sand. 

 Weigh it now in your medicine chest scales, which ought to turn fairly to 

 T ^th of a grain or less. Now if your silver be the Company's standard, 

 the 24 grains (== to 24.00) should give you 22.00. An English shilling 



4 K 



