On some Points in the Chemistry of Acid-manufacture. 371 



likely to suit our purpose, and accordingly drew up a Table of 

 results of analyses which differed to a very great degree from 

 those generally given. In the following Table I. I give in Part I. 

 the amounts of arsenic in the various ores given in Richardson 

 and Watts^s * Chemical Technology ;' and in Part II. my own 

 analyses are given at full length. The differences are very great ; 

 still 1 remain satisfied of the truth of my own results when I 

 consider that the increase in the different specimens obtained by 

 laboratory analysis was an index to the increase obtained as the 

 result of manufacture. 



Table I. 



Part I. 



Name of pyrites. 



Arsenic per cent. 

 Mean. 



Spanish 



0-21 to 0-31 

 trace 

 trace 

 none 

 0-33 

 0-32 

 trace 

 trace 



Belgian 



Westphalian 



Norwegian 



Irish 



Cornish 



Italian . ... 



Swt^dish 



Cleveland 





Part II. 



Arsenic per cent. 



Mean. 



Spanish : — 



Tharsis'... 1-542, 1-620, 1-644, 1790, 1526, 1700, 1-552, 1-661, 

 1-686, 1-796 



1-6517 



1-7453 

 0-9437 

 1-8783 



1-6490 

 1-7085 



Mason's... 1-744, 1 810, 1-891, 1770, 1661, 1692, 1-711, 1-754, 

 1-601, 1-719 



Belgian 1000, 664, 1-621, 0-743, 1002, 0624, 0972, 0924 



Westphalian 1-886, 1-794, 1802, 1936, 1-899, 1-900, 1-921, 1-889 

 Norwegian: — 



Hard ... 1-440, 1-916, 1-633, 1621, 1 648, 1611, 1692, 1-631 

 Soft 1794, 1-731, 1-664, 1-632, 1-700, 1-621, 1-816, 1-709 



Here the Belgian pyrites contains the smallest amount of im- 

 purity ; but this had the fault, on being broken, of crumbling 

 very much and leaving a large amount of " smalls/^ The next 

 in order of purity is the hard Norwegian. This was a good 

 breaking and burning ore, firm, compact, and easily raised to a 

 red heat in the kilns ; so it was found preferable to burn this 

 ore, even with the increased amount of impurity, rather than use 

 the Belgian containing a small amount, but which carried along 

 with it the great inconvenience of making " smalls/^ 



2B2 



