The Purification of Sezvage. 199 



Some recent developments in the application of Salts 

 of Iron to the Purification of Sewage. By Harry 

 Grimshaw, F.C.S. 



(Received May ph^ i8gj.) 



In a previous communication to this Society, I called 

 attention to the action of the perchloride of iron upon the 

 albuminoid bodies which constitute the principal polluting 

 material in sewage and similar waste waters, and showed 

 that the basic perchloride or oxychloride, Fe2Cl6'xFe230H, 

 appears to possess very great precipitating powers in this 

 relation, the action being much quicker and more effectual 

 than that of the normal perchloride FegCle. 



In the present communication I give the results of 

 further work in the laboratory, and on the large scale, in 

 relation to the action of the basic salts of iron upon sewage. 



There being certain technical points which render the 

 basic persulphate of iron more easy to produce and to 

 manipulate, and also less expensive, attention has been 

 devoted to this salt more especially, in place of the basic 

 perchloride. 



With regard to the action of these two substances upon 

 the albuminoid matters of sewage, that of the basic per- 

 sulphate appears to be even more marked than that of the 

 basic perchloride. 



In considering the question of the purification of sewage 

 by the use of the persalts of iron, that is ferric sulphate 

 or ferric chloride, we find, in the first place, that the chief 

 difference between these compounds and the subsulphate 

 (copperas) or subchloride of iron is that the persalts, instead 

 of taking up oxygen from the water or sewage, as do the 

 subsalts of iron, are in the highest possible stage of oxida- 

 tion, and so are induced, under suitable conditions, to part 

 o 



