18-4 



MR. H. A. SMITH ON ARSENIC FROM ALKALI-WORKS. 



Table IV. — Air taken 10 feet from bottom of Chimney. 



(Amount of air taken for each analysis = 500 cubic feet.) 

 No. of analysis. 



Arsenic trioxide 

 per 1 000 cb. ft. 



grain. 

 o'046 



0"022 



0-086 



0*062 



0'II2 



°'°54 



# I22 



CI32 



0*144 



Mean 



0780 

 0-086 



In Table IV. the analyses of some of the air escaping to 

 the atmosphere from the chimney itself are given. 



A small hole was made in the chimney, about 10 feet 

 from the ground, and the passing air aspirated through. 

 As in the former Table (Table III.), the amount of air 

 employed for each determination was 500 cubic feet ; and 

 the number of analyses made was nine. I do not know the 

 amount of air passing in the chimney, so have only calcu- 

 lated the amount of arsenic trioxide per 1000 cubic feet. 



The variation in these specimens is not so great as in 

 the former, being only from 0*022 to 0*114 of a grain per 

 1000 cubic feet. From nine analyses the average amount 

 is 0*086 of a grain per 1000 cubic feet, being below the 

 average in Table III. 



The method employed for collecting the arsenic trioxide 

 contained in the last two tables was very simple. The air 

 was aspirated through three bottles containing respectively 

 (1) water, (2) hydrochloric acid, (3) nitrate of silver. The 

 gas was allowed to bubble very slowly through the solu- 

 tions ; the bottles containing them were capable of holding 



