374 



Mr. H. A. Smitli on some Points in the 



The part from which the deposit was taken was about 15 feet 

 from the furnace. At first sight the deposit seemed to be com- 

 posed merely of common salt and a little sodium sulphate ; but 

 on examination with a hand-microscope, small octahedral crystals 

 of As^ 0^ were distinctly seen. 



Table III. 



Tons. 



Ton As. 



100 



» 



100 

 140-875 



Hard Norwegian pyrites (Table I.) contain, before burning 

 „ „ „ „ afterburning 

 tons. 

 Hard Norwegian pyrites make 140-87o H^ SO*, containing 

 , Sulphuric acid make 104-9 HCl „ 



1-649 

 0-465 



1481 

 0-724 



0059 



M 



204-12 Na-SO^ „ 



In this Table the amounts are given in a manner more useful 

 to manufacturers. 



On analysis this deposit gave (as a mean of nine analyses) 43'4 

 per cent, arsenic trioxide. This flue had been in constant use 

 for some years. (See Table IV.) 



Table IV. 

 Plue from Salt-cake Furnace to Towers. 

 Deposit. 



No. of analysis. 



Arsenic trioxide. 





per cent. 



1. 



44-664 



2. 



42-936 



3. 



45-333 



4. 



39-982 



5. 



46449 



6. 



44-398 



7. 



40-441 



8. 



38-977 



9. 



47-732 





390-912 



Mean 



43-4346 



Coke in condensing -towers. — Although not expecting to find 

 any arsenic in this, thinking that the water in the towers would 

 completely decompose the chloride of arseuic which escaped from 

 the reverberatory furnace, I made an analysis for it. For every 

 analj^sis 10 lbs. of coke were employed, and digested first with 

 pure distilled water and afterwards with perfectly pure hydro- 

 chloric acid. Arsenic was very easily detected in this solution. 

 As an average of three analyses, I find 2-8 per cent, arsenic tri- 



