ACIENTS. PRODUCTe.
Bicarbonate of lime( Chalk 16 oz. = 16 oz. of chalk ii in 900 gallons with Carbonic acid 7 oz.I. 5 Burnt limo in 90 gallons of lime- = 16 oz, of chalk 1.
water 9 oz.
" A small residuum of chalk always remains not separated by the process. Of 174 grains, for Instance, contained in a gallon of water, only 16 grains would be deposited, and 14 grains would remain. In other words, water with 17V of hardness, arising from chalk. can be reduced to 1r, but not lower.
"These explanations wily make it easy to comprehend the successive parts of the doftening process.
" Supposing it vas a moderate quantity of well-water from the chalk-strata around the metropolis that we had to soften, say 400 gallons. This quantity, as has already been explained, would contain 1 lb. of chalk, and would fill a vessel 4 ft. square by 4 ft. deep.
"We would take 9 oz. of burnt lime, made from soft upper chalk; we first slack it into a hydrate, by adding a little water. When this is done, we would put the slacked lime into the vessel where we intend to soften; then gradually add some of the water in order to form lime-water. For this purpose, at least 40 gallons are necessary, but we may add water gradually till we have added thrice as much as this; afterward, we may add the water more freely, taking care to mix intimately the water and the lime-water, or lime. Or we might previously form saturated lime-water, which is very easy to form, and then make use of this lime-water instead of lime, putting in the lime-water first, and adding the water to be softened. The proportion in this case would be one bulk of lime-water to ten bulks of the hard water." It is of importance that the lime-water—that is, the softening ingredient—be put into the vessel first, and the hard water gradually added, because there is thus an excess of lime present up to the very close of the process. Instead of lime-water, the lime itself may be put at once into the vessel, and some of the water to be softened gradually added to dissolve it. The softened water thus obtained has no action on lead pipes or cisterns,
as many soft waters have. One ton of burned lime, used for softening, will produce three and a half tons of precipitate. The present water-supply of the metropolis, if subjected to Clark's process, would deposit about fifty tons of chalk daily.
The process is and has been in successful use ou a large scale at various works con structed under the direction of Mr. Homersham, cm, London, some of them 20 to 25 years since, and others more recently, for softening spring water. derived from the chalk, the oolitic, the lower greensand, and other geological formations, for the supply of Ayles bury, Aston, Clinton, and Mentmore in Bucks; the city of Canterbury with its suburbs, and Herbert hospital, in Kent; Castle Howard in Yorkshire, Caterham, Godstonc, Nut field, liedhill, and Warlingham in Surrey; Park Place Henley in Oxfordshire; Tring in Herts. Works have also been more recently constructed for supplying softened spring water to Sandringham, Norfolk, the seat of his royal highness the prince of Wales, and to Bushey and Stanmore, Middlesex, The process should always he carried out in suitable covered reservoirs, and is then found to be as conveniently applicable, and even more so, for softening large as small quantities; and spring-water varying from 18 to 20 degrees of hardness by Clark's scale is thus readily softened down and supplied to the consumers at from 23 to 43 degrees of hardness. The process for several years past has been in use at Sandhurst, 105 m. n.w. of Melbourne, in Australia, for lessening the amount of organic matter always found to exist in surface-water impounded in large open reservoirs or artificial lakes, and for this purpose is very superior to filtration through sand. Indeed, in the warm climate at Sandhurst, the amount of organic matter becomes so great as to plug up the pores of the sand, and render filtration impracticable.