70 CHEMICAL FERTILIZERS 



There are hence three sources of waste lime from the 

 alkali industry, one from the causticizing plant, one from the 

 sulphur recovery plant and one from the magnesium carbonate 

 works. The difficulty of dealing with these waste materials 

 is due to their small agricultural value and the high cost of 

 handling. The subject of the valuation of fertilizers is 

 discussed on p. 188, where it will be at once seen that 

 materials of this sort are difficult to deal in, on any practical 

 business lines, at a price justified by their agricultural value. 

 The steadily increasing costs of labour render itmore and more 

 difficult to utilize waste materials of low intrinsic value. 

 On the other hand the increasing demands for food produc- 

 tion will compel more complete utilization of all available 

 materials. 



Sulphuric Acid. The manufacture of sulphuric acid 

 is an important part of the alkali trade, but, as much sul- 

 phuric acid is made into superphosphate on the spot, the 

 process is described on p. 128. 



REFERENCES TO SECTION IV. 



Roscoe and Schorlemmer, " Treatise on Chemistry," vol. ii., p. 279 

 (Macmillan). 



Lunge, " The Manufacture of Sulphuric Acid and Alkali," vol. ii. 

 (Gurney). 



Partington, " The Alkali Industry," p. 79 (this series). 



Collins, " Scheibler's Apparatus for the Determination of Carbonic Acid 

 in Carbonates," Journ. Soc. Chem. Ind., 1906, p. 579. 



Hendrick, " The Composition and Agricultural Value of Carbonate of 

 Lime from Causticizing Plant," Journ. Soc. Chem. Ind., 1914, p. 122. 



Hall, " The Book of the Rothamsted Experiments," p. 34 (Murray). 



