Some Aspects of Town Air. 13 



Gaseous matters. — Sulphurdioxide, hydrochloric acid, 

 occasionally nitrous acid, sulphuretted hydrogen and allied 

 bodies emanating from decaying refuse and from sewers, 

 carbonic oxide, and gaseous hydrocarbons. 



Of these impurities, there are many which are unsuited 

 for the purpose of indicating pollution, in consequence of 

 the difficulties attending their estimation, and there are 

 others which have no particular significance. Those which 

 can be readily determined are the soluble sulphur com- 

 pounds, hydrochloric acid and chlorides, suspended organic 

 matter, ammonia and its salts, micro-organisms, and 

 methods appropriate for the estimation of these have 

 already been described. The extent of the variations may 

 be instanced by the following quotations, chiefly gathered 

 from the results published by the Manchester Air Analysis 

 Committee : — 



Sulphur compounds — expressed in volumes of S0 3 per 

 million volumes of air. 



(a) At the Owens College. 



In clear breezy weather, the atmospheric con- \ 01 to 

 ditions being such that free diffusion takes place ) 0*5 



Dull hazy weather in the winter months 2 to 5 



Slight fog 2 to 1 o 



Dense fog iot02o 



(b) In different localities, the time of observation being in each case 



the same. 



The Owens College dei 



ise fog Dec. 



21, 



I892 127 



Hulme (Embden Street)... 



>! 





33 



l6'2 



Town Hall 



33 





33 



150 



Blackfriars Street 



33 





33 



20-8 



Regent Road, Salford ... 



33 





33 



24-8 



University College, London 



33 



Dec. 



22, 



1892 30*1 



St. Bartholomew's Hos- 











pital, London 



33 





33 



38-1 



35 33 5} 



33 



Dec 



2 33 



1892 18-9 



St. George's Hospital, London 



33 





33 



i5-o 



University College, ,, 



13 





33 



IO'O 



Hampstead „ 



33 





)> 



5-8 



