32 Cincinnati Society of Natural History. 



Soap and Alkalies will not i)recii)ilate from the clarified water 

 a perceptable (|uantity of Iron without large concentration. 



Gknkkal Dhductions. 



These experiments tend to confirm the theory of Muspratt, ' 

 that the clarification of water by alum is accomplished by the double 

 decomposition of that Salt and the soluble bicarbonates, forming 

 Aluminic Hydrate, Carbonic Acid and an amount of Sulphates of 

 alkaline earths equivalent to the alum. 



The action of other Salts of Alumina, and also of the Salts of 

 Ferric O.xide, is probably entirely analogous, but when highly con- 

 centrated solutions of the Iron per-salts are used as precipitants, 

 ( )xyhydrates of Iron are formed of considerable weight, which fall 

 out (|uickly. 



When Sulphate of Ferric Oxide is used, the chemical clarifica- 

 tion of the river water introduces into it no substance that was not 

 there before. The entire chemical change in the water consists in 

 the transformation of a few parts in a hundred thousand of the 

 bicarbonates of lime and magnesia into the corresponding Sul- 

 phates, and the Sulphates thus introduced fall much below what 

 exists in the palatable and highly relished hard water of the Lime- 

 stone regions of the Ohio Valley. 



So far as I know, the Per-Sulphates of Iron have not, previous 

 to this investigation, been used for the precipitation of impurities 

 in water. 



Of the above Precipitants, the only one that seems available 

 for use without filtration is the Subsulphate of Iron. 



1. Its use is not followed by an unpleasant taste. 



2. It does not introduce Iron into the clarified water. 



3. The increase of hardness from its use need not exceed 

 the natural variation of the water in hardness. 



4. It introduces no new chemicals. 



5. It will clarify the water without filtration. 



6. It can be produced at a cost comparable with that of alum. 



In view of these points, it was thought best to prepare a sam- 

 ple of the Salt and another series of tests to arrive at the probable 

 cost, and also the effect on sewage impurities in the water. 



I. Muspnitrs Chemistry — \\. Water 



