74 MR. H. A. SMITH ON ARSENIC IN 



accumulated deposit from which we can procure no rela- 

 tive numbers. 



In the chamber itself we find another deposit having 

 here and there beautifully regular crystals, mostly showing 

 transparent elongated prisms, evidently of arsenic acid. 

 On analysis this deposit gave 1*857 P er cen ^. of As, there 

 being present besides large quantities of silica and other 

 insoluble impurities. I am sorry that the observation 

 applied to the previous deposit must also be applied to 

 this, that it has accumulated too long for any useful num- 

 bers to be got from it. However, this shows us so far 

 where the amount of Arsenic missing in the Sulphuric 

 acid has been collected. 



In regard to the products in the manufacture of which 

 Sulphuric acid has been used, we come first to Hydrochloric 

 acid. Of eight analyses, the mean obtained is 0*691 per 

 cent. As. Considering the amount in the Sulphuric acid, 

 this number is comparatively small. I have not been able 

 to examine any of the coke in the condensing-towers ; but 

 I there expect to find a good deal of arsenic collected, as 

 we find only 0*029 per cent. As left in the sulphate of soda. 

 I have also made a few analyses for arsenic of the gas 

 escaping to the chimney from the reverberatory furnace ; 

 but the numbers I do not give at present, hoping to have 

 a more extended series shortly. 



In some samples of soda waste, the production of which 

 I did not see, there was found nearly half a per cent, of 

 arsenic, or 0*442 per cent. This, however, can explain 

 nothing relating to the former numbers, as it came from 

 different manufactories. Still it shows how persistently 

 arsenic sticks to the products, and how difficult it is to get 

 rid of it. 



In twelve analyses of carbonate of soda got from six dif- 

 ferent places of manufacture I was unable to find a trace of 

 arsenic j still I do not feci at all confident on this head, and 



