168 CHEMICAL MANUEES. 



phorus condensing in the tubes and obstructing them. Numerous 

 improvements or alterations on this process have been patented in 

 recent years. Woehler was one of the first to heat phosphate of 

 lime as it occurs in bone ash or phosphatic rocks with silicious sand 

 and charcoal without resorting to the sulphuric acid treatment. 

 Wing's patent, 1891, is based on the same principle. 



Wing's Process. — In Wing's process, bone ash or pulverized 

 rock phosphate and silica are moistened and made into balls which 

 are placed by layers alternating with layers of coal in a cuhilot. 

 The coal yields the incandescent carbon required for the reduction 

 of the phosphoric acid. The silica expels the phosphoric acid fi-om 

 the phosphate as anhydride P^O^, which is reduced to the condition 

 of phosphorus by the incandescent carbon and the reducing atmos- 

 phere. The vapours pass to condensation chambers kept at a 

 temperature of 500° F. (260° C), in which the greater part of the 

 phosphorus is deposited as red phosphorus and the remainder in 

 a water chamber as white phosphorus. The process is continuous, 

 the charge is introduced at the top through the furnace mouth, the 

 residues are evacuated by the grate at the bottom, and two con- 

 densation chamloers are used alternately. 



In using the ordinary furnaces this method was found imprac- 

 ticable owing to the high temperature necessary to treat a charge 

 as refractory as that just indicated. It is well known that 

 electricity can furnish the high temperature necessary, and it was 

 w^ell imagined that it ought to solve the problem, but manufacture by 

 this process has only become possible commercially quite recently, 

 and since the invention of the electric furnace. Consequently the 

 process has been introduced both in Europe and America, where 

 it enables phosphorus to be made at a profit. 



Beachnans Patent. — This process, which dates from 1889, is 

 applied in most countries. The bone ash or the crude phosphoric 

 acid is mixed with ground coal or wood-charcoal. If mineral 

 phosphate be used it is roasted, pulverized, and mixed v/ith wood- 

 charcoal, silica or a basic salt. The mixture is reduced in an 

 electric furnace working continuously in a reducing atmosphere. 

 The currents brought by retort carbon electrode traverse the charge 

 placed between them, acts as a resistance and is heated to incan- 

 descence. The silica combines with the calcium to form a slag of 

 silicate of lime. The phosphorus and carloonic oxide are given 

 off as before. The disengagement commences at 1150" C. and 

 requires a temperature of 1400° C, and even 1500° C. may be reached 

 to complete the reactions. The reaction is the following : — 



2Ca3(PO,)-' + 6SiO, = 6CaSiO, + lOCO + P^ 



Harding s Process. — In Harding's process, 1898, the pulverized 

 rock phosphate is heated with sulphuric acid ; the phosphoric acid 



