24 Cincinnati Society of Natural History. 



Process for Making Hard Water Soft. 

 ist. Clai'k's', for water temporarily hard : 



Add milk of lime equivalent to the carbonic acid that holds 

 metallic carbonates in solution and mix thorou^^hly. 



Holland Process.^ 



Calcined Soda (NaaCOg) 3 Grammes. 



Soluble Glass. Dry. (Soda) i 



TO Grammes of the mixture in 100 c.c. to soften 100 Litres of 

 hard water. 



Process of Clarifcation. 



'I'he i)ractical processes for the clarification of a pul)lic water 

 su])ply seem to be limited to four : 



]st. Subsiding the water in basins. 



2nd. Subsiding in basins after treatment with a precipitant. 



3rd. Filtration. 



4th. Filtration after treatment with a precipitant. 



The first is the one in general use. In this the water standing 

 in basins of large surface and comparative little depth has its whole 

 body subjected more or less to the action of sunlight and to the 

 oxidizing action of the atmosphere. The all)uminous substances, 

 which exist in some cpiantity in all surface waters, and which 

 greatly increase the tenacity with which clay and other solids ad- 

 here to water, are oxidized to mineral matter and fall out together 

 with the solids. 



'I'his is Nature's method for the clarification and jnirification 

 of water, and it is remarkably exemplified in the high degree of 

 purity of all the great lakes of fresh water, and also in the rapid 

 self-purification of all bodies of water of considerable size exposed 

 to air and sunlight when the amount of organic matter is not ex- 

 cessive. 



Subsiding the water in basins after treatment with a precipitant 

 is also an imitation of a process of Nature. 



The exceedingly rapid purification of running streams is clearly 

 the result of the oxidizing effect of the air, rendered more complete 

 by the currents, rapids and eddies that stir the waters, and by 

 l)ringing all parts in succession to the surface, perfectly aerate the 

 whole mass. This effect is further augmented in streams flowing 

 in natural beds in the earth by the mineral substances which are 



1. See Water Analysis. — Wauklyn. 



2. Phar. Praxis. 



