Dr. Turner's Examination of the Oxides of Manganese, 97 



reduced by hydrogen to the state of pure protoxide. I have 

 in no instance estimated the quantity of oxygen by means of 

 the deutoxide, the formation of this compound being in my 

 opinion too uncertain to admit of any analytic process being 

 founded upon it. 



In searching for the presence of foreign matters I have em- 

 ployed the following processes. The water which was expelled 

 from the ores by heat, was examined with test paper, but was 

 always found quite free from alkaline or acid reaction. The 

 absence of carbonates was ascertained by the entire want of 

 effervescence on the addition of dilute nitric acid. Strong sul- 

 phuric acid did not cause the evolution of chlorine or any acid 

 fumes. 



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 com- 

 pletely 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 manganese. By well known methods I satisfied myself of 

 the absence of sulphuric acid, alumina, and magnesia. In se- 

 veral of the ores the oxalate of ammonia detected a trace of 

 lime. It is remarkable 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 man- 

 ganese-ore or black hematite, and the manganese oxide noir 

 barytifere of Haiiy, 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 sulphuric 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 pre- 

 sence, and employed the ferrocyanate of potash and hydrosul- 

 phuret of ammonia as re-agents for its detection. The muriatic 

 solution of the different species yielded a white precipitate with 

 the ferrocyanate 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 

 uncleavable manganese-ore, which has been placed among the 

 ores of iron, are perfectly free from iron, as well as from cop- 

 per, lead, and similar metallic substances. 



Analysis of Manganite or the Prismatoidal Manganese-ore. 

 — This ore, even when selected with the greatest care, yields 

 to distilled water traces of the muriates and sulphates of lime 

 and soda. It dissolves without residue in muriatic acid, and 



New Series. Vol. 4. No. 20. Aug. 1 828. O is 



