162 Dr. Percy on the Composition of Beudantite. 



were identical both in physical and chemical properties with 

 cube-ore ; and that the latter were principally composed of 

 hydrated arseniate of sesquioxide of iron containing in acci- 

 dental mixture oxide or sulphuret of lead. 



Mr. Brooke having supplied me with some of Levy's 

 original specimen of Beudantite, from which the portion ex- 

 amined by Wollaston was taken, I am now able to present 

 quantitative analyses of this mineral. As, however, the quan- 

 tity placed at my disposal was comparatively small, and as 

 "Wollaston mentioned only the presence of oxide of iron and 

 lead, I shall consider it necessary to state somewhat minutely 

 the results of my examination. It wili be seen, by referring 

 to Levy's description previously inserted, that only the black 

 crystals of Descloizeaux agree with that description. 



Qualitative Analysis. 



1. Heated in the closed tube, colourless liquid was given 

 off, which reddened litmus-paper, and produced a white pre- 

 cipitate in a solution of chloride of barium. 



2. A yellow-brown bead was obtained by heating with 

 borax in the outer flame of the blowpipe. 



3. By heating on charcoal in the inner flame with carbonate 

 of soda and a little borax, a dark-coloured bead was produced, 

 from which, by trituration and laevigation, numerous brittle 

 metallic particles and a disc of soft metal like lead were ob- 

 tained. 



4. By roasting the metallic particles (3.) in an inclined open 

 tube, the characteristic odour of arsenic was instantly per- 

 ceived, and a very sensible quantity of white crystalline sub- 

 limate was formed. 



5. The disc of soft metal (3.) dissolved without residue in 

 dilute nitric acid. The solution, evaporated to dryness, gave 

 a white crystalline residue, in the aqueous solution of which 

 iodide of potassium produced a voluminous deep yellow pre- 

 cipitate. 



6. The mineral completely dissolved in hydrochloric acid 

 by the aid of heat, forming a brown solution like that of ses- 

 quichloride of iron. 



7. Solution (6.) was not rendered turbid by dilution with 

 water. 



8. Solution (6.) gave a red-brown precipitate with ammonia, 

 like sesquioxide of iron. 



9. Solution (6.) gave a black precipitate with sulphuretted 

 hydrogen in excess. 



10. Solution (6.) gave a very sensible white precipitate with 

 chloride of barium, not redissolved by dilution with water. 



