270 MACNETICAL PYRITES. 



fulphate of barytes will denote, nearly, 22.50 of fulphur ; fa 



that, with the addition of the J 4< grains previoufly obtained irt 



fubfiance, the total quantity will amount to 36.50. 



XfH mate of the E. Moreover, from what has been dated it appears, that 



pure iron in the lnti iron"' which, was obtained in the form of black oxide, 



weighed SO grains; and, by adding thefe SO grains to the 



36.50 of fulphur, an increafe of weight is found = 16.50. 



This was evidently owing to the oxidizement of the iron, 



■which, in the magnetical pyrites, exifts quite, or very nearly, 



in the metallic ftate, but, by the operations of the analyfis, 



had received this addition. The real quantity of iron muft, 



on this account, be eftimated at 63.50. 



Component One hundred grains, therefore, of the magnetical pyrites^ 



parts yielded, 



Sulphur 4. and 



ouipnur 4. ana - f A i f 1 



36.50 grams. 

 Iron E. = 63.50 



100. 

 Analyfis re- This analyfis was repeated in a fimilar manner, excepting 



peated by acidi- t ] )at { ^ e wno ] e was digefied in nitric acid, until the fulphur was 

 tying all the ful- ... . ° r , . ' 



pbur by nitric intirely converted into fulphuric acid. To the liquor which 



acid. Same re- remained after the feparation of the iron by ammonia, muriate of 

 barytes was added, as before, and formed a precipitate which 

 weighed 24-5 grains. Now, as the fulphuric acid in fulphate of 

 barytes is eftimated by Mr. Chenevix at 23.5 per cent, and the 

 fulphur which is required to form the fulphuric acid contained 

 in 100 parts of fulphate of barytes, at 1 1-.5 *, it follows, that 24-5 

 grains of dry fulphate of barytes, contain fulphuric acid equal, 

 very nearly, to 36 grains of fulphur ; fo that the two analyfes 

 corroborate each other. The proportion of fulphur in the mag- 

 netical pyrites, may therefore be ftated at 36.50, or indeed at 37 

 per cent, if fonie fmall allowance be made for the occafionat 

 prefence of earthy particles ; a minute portion of quartz having 

 been found, by. the laft. anal\ fis, after the complete acidification 

 of fulphur. 



The iron in tbis The increafe produced, by the operations of the analyfis, 



and mail pyrites, j n { ^e weight of the iron, arofe, as I have already remarked, 

 u very nearly in . . ,. . ,. r . . . . , . 



the metallic ' rom the addition ot oxygen ; tor the iron, as obtained by the 



fti!tc - analyfis, was in the ftate of black oxide j but in this, and 



* Tranfaftions of the Royal Irifli Academy, Vol. VIII. p. 240. 

 1 , indeed 



