of the Argillcmous Iroi%-Or&. . ^^ 



more than ordinarily refractory, the flux may be very benefi- 

 cially strengthened by the addition of a small quantity of 

 either of these two substances. They both flux, with nearly 

 equal vigour, either silica or lime, and as they have compara- 

 tively httle tendency to retain the oxide of iron in a state of 

 permanent combination, they are most valuable resources 

 for the assayist in the case of a refractory or a barren ore. 

 We cannot take leave of this subject, however, without clear- 

 ly stating this caution, that neither these nor any saline fluxes 

 whatever should be had recourse to by the assayist, except 

 in those extreme cases where their use can scarcely be dis- 

 pensed with. It is of the utmost importance to the practical 

 metallurgist to maintain a strict analogy between the assay 

 process and mar,ch of the blast furnace : but this analogy is 

 evidently destroyed in the most essential point, when he in- 

 troduces into the assay crucible substances which are never 

 employed in the smelting of the iron-ore on the large scale. * 



Having now considered in what manner a flux should be 

 adapted to each particular class of the argillaceous, the sili- 

 ceous, and other most abundant of our ores, the next object 

 which we have proposed is to point out in what manner the 

 several ingredients which may be required to compose a flux 

 may be obtained by the assayist in sufficient purity. In do- 

 ing this, he will not encounter any difficulty, the substances 

 in question being hme, silica, clay, borax, and fluor spar. We 

 shall subjoin a simple mode of preparing each of them. 



To prepare the lime, let a crucible be filled with pieces of 

 pure white-coloured marble, and then exposed to the intense 

 heat of a furnace for about an hour. Immediately after cool- 

 ing, it should be pulverized, the powder should then be sift- 

 ed with a fine sieve, and secured in a well-stoppered bottle. 

 The reason why it is necessary to pulverize this, and all the 

 other ingredients in an assay, is because it is essential to the 

 success of the operation that all the materials should be ex- 

 hibited in such a form as admits of their being thoroughly in- 

 corporated with each other. 



The uncalcined carbonate of lime, as marble, or any pure 

 common limestone, may be substituted in the assay with 

 little inconvenience for quicklime. But in this latter case. 



