MANUFACTURE OF PHOSPHORIC ACID. 7 
phosphorus from pulverized mixtures of phosphate rock, sand, and 
coke heated to a high temperature in closed containers. Two years 
later (1870) Auberton 13 advocated the use of a blast furnace for 
fusing a mixture of phosphates, silica, and coke and driving off and 
collecting elemental phosphorus; and in 1879 Serve 14 took out a 
patent in which he proposes the use of blocks or bricks of an intimate 
mixture of phosphates and silica bound together by pitch, tar, or 
coal and smelted in a blast furnace. 
The first process for volatilizing phosphoric acid recorded in this 
country is that of Giles and Shearer, 15 who took out a patent in 1888 
for separating this acid from its impurities by passing a current of 
steam over the acid heated to redness. The distillate consisted of 
relatively pure phosphoric acid. In 1889 Headman 16 proposed to 
produce elementary phosphorus by heating in an electric furnace 
(from which air was excluded) a mixture of phosphorus-yielding 
material (in solution), sand, and coke. Two years later (1891) in an 
address before the Society of Chemical Industry 17 this inventor 
stated that he had found it was unnecessary to dissolve the phos- 
phate mineral with sulphuric acid before furnacing, since a mixture 
of sand and coke decomposes it completely at the temperatures 
attained in the electric furnace. This general scheme is the one 
almost universally employed in the manufacture of phosphorus for 
matches and combustible products. In a general way the processes 
of Wing. 18 Duncan, 19 G. C. Landis, 20 and Haff 21 are similar to that 
proposed by Readman, since (with the exception of that of Wing 22 ) 
they all deal with the production of phosphorus by smelting mix- 
tures of phosphate rock, sand, and coke in an electric furnace. Wing 
and Landis, however, claim advantages for briquetted or molded 
charges on the basis that the temperature is more easily controlled, 
dust avoided, and a purer product recovered. 
Ruymbeke 23 appears to have been the first in this country to 
patent a furnace process for the recovery of phosphoric acid rather 
than phosphorus. He advocates the use of a blast furnace for treat- 
ing mixtures of phosphate rock, a reducing agent, and an acid flux, 
introducing into the upper part of the furnace sufficient air to oxi- 
dize any elemental phosphorus. In the processes of De Chalmot, 24 
Maywald, 25 Levi, 26 Haff, 27 and Wilson and Haff 28 mixtures of phos- 
phate rock and silica are heated in an electric furnace, but no reduc- 
ing agent is added. The following reaction is assumed to take place: 
Ca 3 (P0 4 ) 2 + 3Si0 2 = P 2 5 + 3CaSi0 3 . 
It is proposed to absorb the volatilized P 2 5 in water to form 
H 3 P0 4 , and Levi 29 also suggests adding a salt of soda or potash to 
the residual slag in the furnace to make a soluble silicate. 
)3 Readman, J. B. J. Soc. Chem Ind.9,p. 473 22 This inventor proposes the use of a cupola 
(1890). furnace. 
M Idem. 28 xj. S. Patent No. 540124 (1895). 
« U. S. Patent No. 393428 (1888). 24 tj. S. Patent No. 689286 (1901). 
is TJ. S. Patent No. 417943 (1889). ^ TJ. S. Patent No. 902157 (1908). 
"J. Soc. Chem. Ind. 10, p. 445 (1891). 26 u. S. Patent No. 984769 (1911). 
w U. S. Patent No- 452821 (1891). 27 u. S. Patent No. 1076497 (1913). 
" U. S. Patent No. 733316 (1903). 28 TJ. S. Patent No. 1076499 (1913(. 
* U. S. Patent No. 859086 (1907). 29 Loc. Cit. 
" l'. S. Patent No. 1084856 (1914). 
