1922.] The Need for Lime : How to Meet It. 879 



to get the lime into a fine enough condition to apply with a 

 distributor. Tt may be ground (in a disintegrator^* or slaked 

 to form the hydrate Ca(OH)^. There is only one method 

 known to the writer by which lime may be ground without 

 making so much dust that the tending of the plant is almost 

 beyond human endurance, and that one method consists in 

 mounting the disintegi-ator on the top of a large air- and dust- 

 tiofht storage bin (with sacking mouths at the bottom alwav^ 

 sealed by ground lime). A wooden or sheet metal tube is led 

 from the top of the bin into the feed mouth of the disintegrator. 

 This tube suffices to return the dust-laden air, which is 

 <"irculated by the fanning action of the disintegrator, to the 

 machine again , and no air escapes to carry with it irritating 

 lime dust. This arrangement obviates settling chambers, dust, 

 T)alloons. etc.. with all their ineffieienc}^ and expensive upkeep. 



If it is decided to produce the hydrate, there is no necessity 

 for a small concern to invest in any of the numerous hydrators. 

 The essential thing is that water should be added in the right 

 quantity and the right way to the lime when it is freshly burnt. 

 The quantity of water needed is a hundred gallons per ton of 

 quicklime. Theory requires that only 72 gallons should be 

 added, but it is necessary in practice to allow for the water lost 

 in steam, which is given off when the lime and water have been 

 in contact for a short time. A good deal of evaporation also 

 occurs during the mixing. 



Many different methods of adding the water to the lime have 

 been advocated, but if the correct proportion of water is strictly 

 adhered to and an even distribution, followed by a thorough 

 mixing, is secured, it matters little what the exact procedure 

 may be. After mixing, the hme should be left undisturbed for 

 24 hours to allow the reaction to com.plete itself. Then, if the 

 product is to be applied by means of a distributer, it must be 

 screened through a } in. or even finer screen to remove core, 

 ash. flints, etc. 



Lime hydrated in this way is an excessively fine, dry powder 

 ;and can be safely stored in bags, as it will not swell like ground 

 tjuicklime and burst the bags. It only takes up carbon dioxide 

 from the air very slowiy; not more than about 4 per cent, is 

 found to be converted to the carbonate after exposure to the 

 air in bags for a whole year. It therefore almost ranks with 

 ground limestone so far as its convenience in handling and its 



* For description of these machines see the June issue of the Journal 

 (p. 204). 



