118 A. KING THE ADVANTAGES 



into the chalk to dissolve some of the carbonate of lime on its way. 

 With regard to water from deep wells in the chalk, the Duke of 

 Richmond's Commission on the Pollution of Elvers made the 

 following i^eport in 1874: — "The unpolluted deep well waters 

 from the Chalk rank amongst the best and most wholesome with 

 which we have become acquainted. They are almost invariably 

 colourless, palatable, and brilliantly clear. . . . The Chalk con- 

 stitutes magnificent underground reservoirs in which vast volumes 

 of water are not only rendered and kept pure, but stored and 

 preserved at a uniform temperature of about 50° Y., so as to be cool 

 and refreshing in summer and far removed from the freezing 

 point in winter. It would probably be impossible to devise, even 

 regardless of expense, any artificial arrangement for the storage of 

 water that could secure more favourable conditions than those 

 naturally and gratuitously afforded by the Chalk ; and there is 

 reason to believe that the more this stratum is drawn upon for 

 its abundant and excellent water, the better will its qualities as 

 a storage medium become. Every 1,000,000 gallons of water 

 abstracted from the Chalk carries with it in solution on an average 

 H ton of the chalk through which it has percolated, and thus 

 makes room for an additional volume of about 110 gallons of water. 

 The porosity or sponginess of the chalk must therefore go on aug- 

 menting, and the yield from wells judiciously sunk, ought, within 

 certain limits, to increase with age. The only di'awback to these 

 waters is their hardness, but this disadvantage is greatly reduced 

 by the circumstances that it is chiefly of the ' temporary ' kind, 

 and can be therefore easily and cheaply removed by the application 

 of Clark's process." 



Let us consider next more fully the meaning of hardness as 

 applied to the action of the chalk on soap. In chemistry we 

 recognize two distinct classes of compounds, acids and bases ; these, 

 having the property of uniting, together forming a third class 

 called salts. Carbonate of lime is a salt formed of the base, quick- 

 lime, and the acid, carbonic acid gas. Soap in the same way is a 

 salt formed of the base or alkali, soda, and some rather complex 

 organic acids called fatty acids. It often happens that when the 

 two salts are brought together in solution the acid of the one goes 

 to the base of the other and vice versd, two new salts being formed 

 as a conseqiience ; and although both the original salts might be 

 soluble in water, it does not follow that these new salts formed are 

 soluble also. This is the case when chalk and soap come together 

 in solution. The chalk which is soluble by virtue of the carbonic 

 acid gas in the water reacts on the soap and the base of the gas, 

 and c[uick-lime unites with the fatty acids of the soap, giving rise 

 to the white, curdy, insoluble salts that we see floating on the top 

 of hard water when we try to wash in it, the soda of the soap or 

 base uniting with the acid of the chalk to form carbonate of soda ; 

 so that instead of chalk and soap we get carbonate of soda and 

 lime salts of the fatty acids. 



If we want to do away with this property of hardness, how are 



