PYRITES AND VARIOUS PRODUCTS. 75 



expect that I may still come across some specimens con- 

 taining at least a " trace." 



Some samples of Sulphur recovered by Moneys process 

 gave a very large amount of arsenic, 07002 per cent. ; but 

 this was before it had undergone the process for purification, 

 as I have since had some prefectly free and pure. 



Table III. 



Tons. Ton As. 



1 00 Hard Norwegian pyrites (Table I.) contain, before burning 1-649 



,, ,, ,, „ after burning 0*465 



Tons. 

 1 00 Hard Norwegian pyrites make 140*875 H 2 S0 4 , containing 1 -48 1 



140*875 Sulphuric acid make !04'9 HC1 „ 0*724 



„ „ „ 204*12 Na 2 S0 4 „ 0*059 



In this Table I have given the numbers on a practical 

 scale, so that one may see the amount of impurity we have 

 to deal with. Viewed in this way it looks really serious. 

 In every 100 tons of pyrites we have \\ ton of arsenic, and 

 nearly half a ton left in the burnt residue. The difference, 

 or 1 ton, spreads itself through the whole process of soda- 

 making. 



If the arsenic is to be expelled at all, it must be ex- 

 pelled from the sulphuric acid. In some places this is 

 already in operation; but this process always carries with 

 it the other great inconvenience, not only to ourselves but 

 to our neighbours, of the disagreeable smell of sulphu- 

 retted hydrogen. In some places in Germany, in the 

 Hartz &c, I believe they clear the acid by simply passing 

 this gas through it ; it is, however, difficult to imagine how 

 this can possibly be remunerative. However, this is one of 

 the many open questions in alkali manufacture the working 

 out of which will be a gain to the manufacturer. 



Arsenic is not only an expensive impurity to the manu- 

 facturer, extending itself to the products, but it also acts 

 upon the nitric acid in the lead-chamber. 



