282 Dr Colquhoun on the Assaij 



stopper, and counterpoise the bottle with its contents upon a 

 balance. A determinate quantity of the ore (as from 50 to 100 

 grains) is next to be weighed oiit ; it ought to be previously 

 reduced to the form of small grains like coarse gunpowder, but 

 none of it should be finely pulverized. Put a small portion of 

 it into the bottle, then replace the stopper, and agitate the 

 mixture occasionally. An effervescence will take place, occa- 

 sioned by the disengagement of carbonic acid gas. The stop- 

 per will readily permit the escape of the gas, but will retain 

 any particles of liquid which the gas may carry up with it me- 

 chanically. When solution is nearly accomplished, introduce 

 an additional quantity of the ore into the bottle, and let this 

 process of adding the ore in small successive portions be re- 

 peated, until the whole is used. When the solvent power of 

 the acid begins to be weakened, towards the conclusion of the 

 process, it may be assisted by heating the bottle very gently ; 

 the temperature must not exceed 90% otherwise a portion of 

 muriatic acid would be expelled along with the carbonic acid 

 gas. When the action of the acid on the ore is completed, set 

 the bottle aside for two hours, in order that it may recover the 

 temperature of the atmosphere. Then remove the stopper,' 

 and having introduced into the bottle a narrow tube, draw out 

 the carbonic acid gas that it contains, which will thus be re- 

 placed by atmospheric air. Nothing now remains except to 

 place the bottle once more upon the balance, and ascertain the 

 addition of weight which it has acquired. This increase indi- 

 <jates the weight of all the ingredients of the ore, with the ex- 

 ception of the carbonic acid ; by subtracting it, therefore, from 

 the original weight of the ore, the quantity of the carbonic 

 acid may be ascertained. »5 



By this method of analysis, the assayist may always be 

 able to discover the true constitution of any of his iron-ores, 

 and he will find thaf: the result of his investigation determines, 

 with extreme precision, the nature of each constituent of the 

 mineral, and also its relative amount. When these are suffi- 

 ciently known, he has only to attend to the affinities considered 

 in page 255, in order to adapt the most appropriate flux to his 

 ore, so that with the smallest expenditure of time and fuel, he 

 may receive the largest return of metal for the furnace which 



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