THE MANUFACTURE OF PHOSPHORUS. 167 



APPENDIX. 



THE MANUFACTURE OF PHOSPHORUS IN THE ELECTRIC 



FURNACE. 



In a recent publication of the United States Geological Survey, 

 entitled " The Production of Phosphate Rock and Phosphorus in 

 1906," G. W. Stose makes an interesting summary of the progress 

 made in phosphorus manufacture, and points out the role which the 

 electric furnace has played in this development. Formerly phos- 

 phorus was only extracted from bones and other organic matter. 

 It is only quite recentlv that it has been extracted from mmeral 

 products."^ First of all, phosphorus was extracted from phosphatic 

 rocks, such as the impure fluophosphates of calcium, with which 

 the superphosphates used in agriculture are generally made. 

 Apatite, which is a fluophosphate or a chlorophosphate of calcium, 

 was only used to a slight extent in Europe or in Canada. Quite 

 recently wavellite phosphate of alumina has been used as a source 

 of phosphorus. It is furnished in sufficient quantity for the purpose 

 by deposits situated at Mount Holly Springs (Pennsylvania). The 

 old process of phosphorus manufacture which was m use m the 

 beginning of the nineteenth century is as follows. The bones are 

 burnt, then ground ; the bone ash superphosphate of lime is treated 

 by a sufficient quantitv of sulphuric acid to convert the whole or a 

 part of the calcium into calcium sulphate and the phosphorus into 

 metaphosphate of calcium and even into phosphoric acid, which is 

 concentration by evaporation mixed with wood charcoal and reduced 

 bv heating in a furnace in a fireclay retort. The vapour of phos- 

 IDhorus and carbonic oxide is given off. The phosphorus which is 

 condensed under water has a waxy appearance and yellowish 

 colour. Theoretically the reaction should be : — 



2Ca3(PO,)o + 6H,S0, + 12C = 

 6CaS0, +"12C0 + P4 + ^H.O 



Practically, however, it is found that the following reaction better 

 represents what occurs : — 



3Ca3(PO,)- + 6H.,S0, + IOC = 

 6CaS0, + Ca3(P0,^ + lOCO + P, + 6Hp 



In this process the loss due to destruction of the retorts by sulphuric 

 acid and bv the great heat is considerable. Only a portion of the 

 phosphorus therefore present in the charge is recovered. There is 

 also the danger of seeing the phosphorus inflame when withdrawn, 

 and it is necessary to take the greatest care to prevent the phos- 



