THE MANUFACTUEE OF PHOSPHORIC ACID. 165 



of fruit collected in the squares so treated before the raspberries in 

 the plants cultivated without manure were ripe (end of April). Now 

 the amount used hardly came to the value of Is. 



Bisulphate Superjjkosphate.—lt now remains to say a word 

 «,bout another product absolutely unpublished, i.e. the bisulphate 

 superphosphate. Bisulphate, as is well known, is a bye-product 

 of the manufacture of nitric acid, and finds hardly any use, except 

 in glass works and in the manufacture of Glauber s salt. But it is 

 difficult to sell, and it is got quit of at any price, for the local 

 authorities forbid it being run into streams. Dr. Graeber tried to 

 utilize it in the manufacture of superphosphates. By mixing 500 

 kg. of bisulphate with 150 kg. of Algerian phosphate he obtained 

 a superphosphate, but the product was very deliquescent because 

 it wanted the water of constitution necessary to the formation of 

 sulphate of lime. Dr. Grueber remedied that by adding to the 

 phosphate 60 kg. of water. He thus obtained a dry superphosphate, 

 with 7 to 8 per cent of soluble phosphoric acid ; the addition of a 

 small amount of Algerian phosphate enabled it to be passed through 

 . the centifrugal crusher and to obtain it in a pulverulent form. As 

 all manure factories require low superphosphates to adjust the 

 analysis, this product would thus readily find a use.i 



Phosphatic Peat. — It now remains to describe a manure m 

 which the phosphoric acid is present, not in chemical combination 

 but in simple admixture — we mean phosphatic peat. In 1892 

 the Society of German Agriculturists greatly recommended the 

 manufacture of this product as a microbicide, as a preventative of 

 epidemics, and fit to render both human and animal excreta in- 

 offensive. The first steps made in this direction with hydrochloric 

 and sulphuric acid have not given conclusive results ; hydrochloric 

 acid is too volatile, sulphuric acid carbonizes the fibre of the peat, 

 so that it is difficult to use more than 2 per cent in the mixture. 

 Phosphoric acid has not that drawback, and there is nothing there- 

 fore to prevent phosphatic peat being prepared with 10 to 15 per 

 cent of P2O.-. Experiments on a manufacturing scale, and applica- 

 tion of this procLuct, were made in 1893 by Dr. Meyer, who, more- 

 over, exhibited samples at the show of the German Society of 

 Agriculturists, who made him an award. There is no doubt that 



1 A.fter the afcid over and above that required to form the normal sulphate 

 of poda was killed by the pho-phate, the water very evidently acted by com- 

 bining with the excess of sulphate of soda to form Na2SO^,10H.,O, an elHorescent 

 salt. The "free" acid must have formed sulphate of lime ab initio or the 

 phosphate could not have been dissolved. Of course the water would enable 

 the dissolved phosphite of lime to react on the excess of sulphate of soda to 

 produce phosphate of soda and sulphate of lime. But why not send the bi- 

 sulphate up the cups and mix it in the mixer with the acid and phosphate in 

 the usual way ? This seems to have been a sort of compost heap, and the fewer 

 of these about a factory the better. — T^ . 



