Clarification of the Piiblic Water Supply of Cijicinnati. 2 1 



Synopsis of Published Material. 



The published work in reference to the separation of finely 

 comminuted matter from water that holds it in suspension is for 

 the greater part contained in papers treating on dynamical Geology, 

 and has been developed in the investigation of the causes which have 

 produced the varied and extensive formations resulting from Sedi- 

 mentation. 



T. Sterry Hunt' has shown that the mud held in suspension 

 in the water of the Mississippi River is completely precipitated out, 

 and the water becomes clear in from twelve to eighteen hours by 

 the action of Sea Water, Common Salt, Epsom Salt, Alum, or Sul- 

 phuric Acid. 



Brewer-, after many experiments with various precipitants 

 upon water mixed with clay, both as found naturally in turl)id 

 streams or artificially prepared by himself with different kinds of 

 clay, arrives at the hypothesis that the clay held most tenaciously 

 suspended in water is combined with it in the colloid form. He 

 leaves the reader to make the deduction natural to the case, that 

 the action of a precipitant in clarifying the water is to break up the 

 colloid molecules that hold the solids in suspension, which then 

 fall out by gravity. 



D. Waldie^, on investigating the water supply of Calcutta, 

 with reference to the use of the water of the Hoogly River, reports 

 that certain salts have the power of coagulating the clay held in 

 suspension in turbid river water. The most prominent of these are 

 the Salts of Alumina and Ferric Oxide. It may also be accom- 

 plished by alkalies, alkaline earths, and also by the acids, Nitric 

 Acid, Muriatic Acid, Acetic Acid and Sulphuric Acid. 



Waldie's Table*. 

 The following table is given by Waldie, showing the relative 

 weights of the substances named recjuired to produce the same re- 

 sults in precipitation : 



Common Salt 4680 



.Caustic Potash 560 



Bicarbonate of Soda 672 



Acetic Acid 360 



1. Society of Nat. Hist. Report, Boston, Mass., February. 1S74. 



2. Memoirs of the National Academy of Sciences, U. ii. A., 1SS3; and American 

 Journal ol Science, January, 1SS5. 



3. Journal of the Asiatic Society of Bengal IT. 1S73. 



4. Chemical News II. 1S73. 



