ALKALI INDUSTRY BY-PRODUCTS 69 



with much lower proportions of water it becomes too dusty, 

 and blows about with the least wind. The material is so 

 finely divided that it behaves in the soil like clay, and, unless 

 carefully distributed, it may remain in lumps in the soil for 

 years without breaking up ; but, being porous, any portions 

 that come near the surface are easily broken up by frost. 



Sodium Sulphate. At Rothamsted this material has 

 been found to have a real fertilizing value ; unfortunately, 

 it is not generally considered in the manufacture of fertilizers. 

 It is a product of the alkali industry (see p. 66), and can be 

 obtained readily. 



Magnesium Carbonate Wastes. Magnesium carbonate 

 can be made from the limestone of the Permian series. By 

 Pattinson's process, dolomite, or magnesium limestone, is first 

 of all ignited, and then treated with water and carbon dioxide 

 under pressure. Under these circumstances, the mixed 

 oxides of calcium and magnesium formed on ignition are 

 carbonated, the magnesium carbonate dissolving in the 

 carbonic acid far more readily than calcium carbonate. The 

 solution of magnesium bi-carbonate thus formed is separated 

 from the insoluble calcium carbonate, and subsequently 

 decomposed by a current of steam into insoluble magnesium 

 carbonate and carbon dioxide. The residual calcium 

 carbonate is usually comparatively free from magnesia, and 

 is, therefore, suitable for application to the land. It is rather 

 denser than Chance mud, and is consequently slightly easier 

 to apply to the land. Again, no great expense is justified 

 in dealing with this material, but provisions, similar to those 

 described for Chance mud, will serve to dispose of most of 

 these lime wastes. In districts where fairly pure lime can 

 be obtained at moderately low prices, it is difficult to cover 

 the costs of handling these waste materials, since in no case 

 are they sufficiently concentrated to allow two tons to do 

 the work of one ton of high quality burnt lime. In districts 

 where high quality burnt lime is only obtained with diffictilty 

 and at high cost, these industrial lime wastes are extremely 

 important in agricultural practice, and every effort should 

 be made to utilize them to the maximum extent. 



