118 PURIFIERS. 



The lime is used both as a hydrate and in the fluid state, in the following 

 proportions : For the purification of 1,000,000 cubic feet, the produce in the 

 winter season of twenty-four hours, eighty bushels mixed as " dry lime," and 

 twenty bushels mixed into a fluid : this quantity performs its part thoroughly. 



At Cheltenham 1^ bushel of quicklime, reduced to the state of a hydrate, 

 will purify 10,000 cubic feet of gas perfectly : cost per bushel from 5d. to 6d. 



At Birmingham the purification of 1000 feet costs, in lime and labour, from 

 \\d. to \\d. t but in reality not nearly so much, as the refuse is sold for 

 two-thirds the original cost of the lime. Lias lime is used, and " dry puri- 

 fiers." 



With the dry-lime purifiers at Chester 1 cwt. 2 qrs. is required to purify 

 10,000 cubic feet of gas. The Welsh lime is used, its price being 13*. 4d. per 

 ton; therefore the purification of 10,000 feet will cost 12d. without labour, 

 which is about the average cost. 



In conclusion, I may observe, that in making the dry lime-purifiers, that 

 they may present a sufficient surface to the gas which passes through them, an 

 excess, rather than a smaller area, should be given. A bushel of lime, when 

 reduced to the state of a hydrate, contains very nearly 4500 cubic inches : al- 

 lowing that this quantity will purify 5000 cubic feet, it follows that 12'5 square 

 feet of screen surface is required, the depth of the lime being 2'5 inches. 



From the retorts contained in the building represented in Plate IX., 

 300,000 cubic feet of gas may be produced in twenty-four hours. The puri- 

 fiers should present a surface of at least 750 square feet. If three machines 

 are worked together, each containing five screens, their dimensions may be 

 8 feet 6 by 6 feet, and 3 feet deep, four bushels of hydrate of lime being spread 

 on each screen. The surface presented by the three machines in Plate XIII. 

 is 324 square feet : they were erected for an establishment producing 130,000 

 cubic feet of gas in twenty-four hours. 



The work performed by a lime-water purifier is generally computed by its 

 contents in gallons, and the head of water or pressure opposed to the passage 

 of the gas through it. Taking the latter at a constant quantity of eight inches, 

 the computation is easy. 4500 cubic inches of hydrate of lime, (which has 

 been before stated is the quantity produced by reducing one bushel or 2150 

 cubic inches of quicklime) mixed with forty-eight gallons of water, will pu- 

 rify 10,000 cubic feet of gas, if properly applied. In the example at Plate 

 XIV. the lime-machine contains 316 gallons, which will hold in solution thir- 

 teen bushels of hydrate of lime, and purify 65,000 cubic feet of gas. Two of 



