164 Dr TURNER'S Chemical Examination 



On dissolving the ores in muriatic acid and evaporating the 

 solution to perfect dryness. the residue, with the exception of a 

 little siliceous matter and red oxide of manganese proceeding 

 from slight decomposition of the chloride, was always complete- 

 ly redissolved by water. This circumstance demonstrates the 

 absence of phosphoric and arsenic acids, which, if present, would 

 have been left as the insoluble phosphate or arseniate of manga- 

 nese. By well known methods I satisfied myself of the absence 

 of sulphuric acid, alumina, and magnesia. In several of the ores 

 the oxalate of ammonia detected a trace of lime. It is remark- 

 able that every species, with one exception, contains baryta. In 

 most of them, indeed, it is present only as an impurity ; but in 

 two of the ores, the uncleavable manganese-ore or black hema- 

 tite, and the manganese oxide noir barytifere of HAUY, it is an 

 essential ingredient of the mixture. In those species in which 

 this earth exists as an impurity, it is not united with the sul- 

 phuric or carbonic acid; but is most probably combined with 

 the peroxide of manganese. 



From the frequency with which iron has been found accom- 

 panying the ores of manganese, I was led to expect its presence, 

 and employed the ferrocyanate of potash and hydrosulphuret of 

 ammonia as re-agents for its detection. The muriatic solution 

 of the different species yielded a white precipitate with the ferro- 

 cyanate of potash, and the characteristic flesh-coloured sulphuret 

 of manganese with the hydrosulphuret of ammonia. It hence 

 follows that all the ores submitted to analysis, even the uncleav- 

 able manganese-ore, which has been placed among the ores of 

 iron, are perfectly free from iron, as well as from copper, lead, 

 and similar metallic substances. 



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