1824.] Mineral Substances before the Blowpipe. 37 



baryta will be known by the greenish -yellow, and strontita by 

 the crimson colour it imparts to the flame. By employing only 

 three fluxes, carbonate of soda, borax, and the triple phosphate 

 of soda and ammonia (salt of phosphorus), with the occasional 

 use of the nitrate of cobalt, we can readily ascertain the presence 

 of silica, alumina, magnesia, and almost all the fixed metallic 

 oxides ; and by the further examination of the fused globule, 

 especially that with carbonate of soda, by dissolving it in a 

 drop of muriatic or nitric acid, on a slip of glass, and applying 

 the proper tests, unequivocal evidence may be obtained of the 

 presence of any of the other earths or oxides of which the sub- 

 stance is composed, and even a tolerable estimate may fre- 

 quently be formed of their respective proportions. By substi- 

 tuting nitrate of baryta as the flux, and using a slip of platina 

 foil for the support, instead of the wire, the presence of either of 

 the alkalies may, by the usual well-known processes, be de- 

 tected, with equal ease and certainty, on the same minute scale 

 of operation. 



An advantage peculiar to this microscopic chemistry is the 

 very small quantity of matter that is sufficient for examination, 

 which may generally be detached from rare and costly speci- 

 mens without injury, whereas for operations on a larger scale, it 

 is necessary wholly or in great measure to destroy them. When 

 the exact proportions of the ingredients of a mineral are required, 

 recourse must necessarily be had to more elaborate processes, 

 but even then previous examination by the blowpipe is of essen- 

 tial service, since by indicating the different substances present, 

 it enables us to determine the most advantageous method to be 

 adopted in the subsequent analysis. Convinced of the utility of 

 this sort of investigation, I propose, from time to time, to pub- 

 lish in the Annals the blowpipe characters of such minerals as 

 have not already been so examined. For those which form the 

 subject of the present communication, I am indebted to the 

 kindness of Mr. Brooke. 



1. Arfwedsonite. (Phillips's Mineralogy, p. 377.) 



Atone in the glass matrass, gives off a very little moisture at a 

 red heat : no decrepitation ; appearance of the assay scarcely at 

 all altered. 



Alone in platina forceps, swells up, and fuses with great ease 

 into a brilliant, opaque, black globule. 



With soda, on platina wire, in the oxidating flame, fuses 

 readily into a dark-brown opaque globule, while hot; olive- 

 green, cold. By the addition of nitre the green colour becomes 

 much brighter. In the reducing flame the colour changes to a 

 dark, slightly greenish-brown. 



With borax, dissolves readily, and gives a transparent globule 

 of a garnet-red colour, hot, which changes to a deep wine-yellow 



