172 Dr. C. A. Burghardt on the 



methods have been devised for arriving at satisfactory- 

 results by modifying, in various ways, the well-known 

 fusion processes, but so far without very much real 

 improvement. 



I venture to-night to lay before you a general process 

 which deals with all the refractory silicates, several refractory 

 oxides and compounds of oxides, and some other insoluble 

 mineral compounds. I am still occupied in ascertaining 

 whether this process is applicable in the case of minerals 

 where sulphur, arsenic, and antimony enter largely into 

 their composition, and hope later on to lay the results 

 obtained before this Society. After many experiments I 

 found that the best results were obtained by mixing the 

 finely divided mineral with about ten per cent of its weight 

 of finely divided charcoal, and projecting the mixture care- 

 fully into a silver crucible containing fused hot caustic soda 

 or potash, about six times the weight of the mineral powder 

 taken for analysis. The crucible and its contents are then 

 carefully heated over an ordinary Bunsen-burner until the 

 reaction arising has taken place, this point being easily 

 ascertained by the fact that all further evolution of com- 

 bustible gas has ceased, and the mass remaining in the 

 crucible has become dry, and generally white or grey in 

 colour. From the experiments which I have made I con- 

 clude that hydrogen gas is evolved from the caustic alkali, 

 and possibly a small quantity of carbon monoxide, whilst 

 undoubtedly carbon dioxide is largely produced by the 

 combination of the carbon with the oxygen of the caustic 

 alkali and the oxygen of the oxides present in the minerals 

 taken for analysis. Further, there is no doubt in my mind 

 that metallic sodium or potassium is liberated during the 

 course of the reaction, and these metals, whilst in the 

 status nascendi, combine either with the metallic oxide 

 (as in the case of oxide of zinc and oxide of tin) or with 

 the acid present in the minerals. The latter conclusion 



