Section III, 1918 [141] Trans. R.S.C. 



The Utilization of Nitre Cake in the Manufacture of Superphosphate 

 By Frank T. Shutt, D.Sc, and L. E. Wright, B.Sc. 



(Read May Meeting, 1918) 



Notwithstanding the advances that have been made of late years 

 in the utihzation of chemical by-products, nitre cake — essentially 

 sodium bisulphate — the residue from the manufacture of nitric acid 

 from Chili Saltpetre, must be regarded as a waste product and practic- 

 ally valueless. Many uses have been proposed for it, but only a few 

 of these have proved profitable or of any commercial importance. 

 The literature on the subject is voluminous and we find on record the 

 results of a very large amount of investigatory work of the very highest 

 order, but apparently the problem still awaits a successful issue. 

 Even in peace times this by-product has accumulated and proved 

 an expensive nuisance; in these days when it is being produced in 

 millions of tons its disposal has become a very serious matter. Where 

 location permits it to be discharged into tidal waters it is most cheaply 

 and possibly least objectionably got rid of, but inland its disposal 

 means, generally, the pollution of streams and lakes and the destruc- 

 tion of fish or the ruination of land. It is evident that a fortune 

 awaits the one who can find a profitable use for it in large quantities. 



Of the almost innumerable processes that have been brought 

 out or suggested it would be quite impossible in this paper to give 

 any account, but a few of the uses that nitre cake has been put to 

 may be enumerated, for the purpose of showing the wide range of in- 

 vestigational activity in this matter: the production of hydrochloric 

 acid and salt cake by furnacing with salt; the pickling of metals; 

 the extraction of grease from wool; the bleaching of lace, etc; mineral 

 water manufacture; the manufacture of crude ferric sulphate for 

 sewage precipitation; the preparation of sodium sulphide; the separ- 

 ation into Glauber's salt and free acid and lastly, though by no means 

 is the list exhausted, as a diluent for sulphuric acid in the manufacture 

 of superphosphate. It is in connection with this latter use, though 

 not employing sulphuric acid, that the work recorded in this paper 

 was undertaken. 



This preliminary investigation was taken in hand at the instance 

 of the Metallurgical Division, Explosives Department, Imperial 

 Munitions Board, which was anxious to find some useful purpose for 

 the large amount (about 150 tons daily) of nitre cake produced at 



Sec. Ill, Sig. 11 



