3 22 
Mr. Hatchett's Analysis 
an increase of weight is found = 16.50. This was evidently 
owing to the oxidizement of the iron, which, in the magnetical 
pyrites, exists quite, or very nearly, in the metallic state, but, by 
the operations of the analysis, had received this addition. The 
real quantity of iron must, on this account, be estimated at 
% 5 °- 
One hundred grains, therefore, of the magnetical pyrites, 
yielded. 
This analysis was, repeated in a similar manner, excepting 
that the whole was digested in nitric add, until the sulphur was 
intirely converted into sulphuric acid. To the liquor which 
remained after the separation of the iron by ammonia, muriate of 
barytes was added, as before, and formed a precipitate which 
weighed 245 grains. Now, as the sulphuric acid in sulphate of 
barytes is estimated by Mr. Chenevix at 23.5 per cent, and the 
sulphur which is required to form the sulphuric acid contained 
in 100 parts of sulphate of barytes, at 145,* it follows, that 245 
grains of dry sulphate of barytes, contain sulphuric acid equal, 
very nearly, to 3 6 grains of sulphur ; so that the two analyses 
corroborate each other. The proportion of sulphur in the mag- 
netical pyrites, may therefore be stated at 36.50, or indeed at 37 
per cent, if some small allowance be made for the occasional 
presence of earthy particles ; a minute portion of quartz having 
been found, by the last analysis, after the complete acidification 
of the sulphur. 
• Transactions of the Royal Irish Academy, Vol. VIII. p. 240, 
Iron E. 
%5o 
100 . 
