160 CHEMICAL MANURES. 



material, but that is too clear. Nevertheless, in 1892, the Biebrich 

 factory produced small quantities of phosphate of potash by satura- 

 tion of potash by phosphoric acid, although the product was of 

 bad quality (much insoluble P^Or, and H._,0}. 



Manufacture of Sulplio-phosphates. — During this time chemists- 

 tried new methods of manufacture. At that time Dr. Paul Wagner, 

 1892, published his pamphlet on the use of chemical manures in 

 horticulture, and gave the idea of manufacturing pure and con- 

 centrated chemical manures. This idea was taken up by H. Albrecht, 

 director of the Biebrich factory, which henceforth manufactured 

 phosphates of potash and ammonia and nitrate by mixing the 

 ingredients in different proportions. As a matter of fact, a sort of 

 phosphate of potash was known as early as 1886, but its percentage 

 of sulphuric acid rendered it unfit for the purposes to which such 

 mixtures are applied. This product is the sulpho-phosphate of potash 

 which was at first made by Meyer, as well as an analogous product, 

 the sulpho-phosphate of ammonia. 



The sulpho-phosphates are interesting from several points of 

 view, and possess such valuable properties that thei'e is reason 

 to ask why agriculture and the chemical manure trade do not make- 

 more frequent use of them. So long as the Wetzlar f actor v was at 

 work, it produced great quantities intended chiefly for export to the 

 Dutch East Indies, but from that time they have not been heard of. 

 If equal parts of 55 per cent phosphoric acid and of sulphate of 

 ammonia or sulphate of potash be mJxed together and heated to 

 80" C, the components unite, and form a dry pulverulent salt. An 

 addition product of the two substances is formed : — 



Am.,SO^ + H3PO, - AmHSO^ + AmH.PO, 

 K2SO, + H.PO, = KHSO, + KH.PO^ 



The product contains respectively, 25 per cent P.^O^ and 10 5 N, and 

 21 per cent P2O- and 27 per cent K,0. The phosphoric acid is present 

 in a condition almost entirely soluble in water. The percentage of sul- 

 phuric acid is about 30 per cent. (Peculiar thing, an analogous com- 

 pound cannot be obtained from soda in this way.) The manufacture 

 is exceedingly simple. There is dissolved in the "weak solution,'" 

 obtained in the manufacture of phosphoric acid ; an equivalent quan- 

 tity of alkaline sulphate, viz. 100 Am^SO^ for 55 Pp^ and 100 K.^SO^ 

 for 18 P.20;^, and the solution is evaporated until the boilino-point 

 rises to llO'' C. (230' F.) for the potash salt and 140' C. (284° E.) for 

 the ammonia salt. Finally, the hot mass is run into a cooling beck 

 and agitated until it solidifies. This process is much more simple 

 and cheaper than that of making double superphosphate. It is well 



