MANUFACTURE OF PHOSPHORIC ACID. 53 
ton (or 31 cents per unit) of P 2 5 in the form of double acid phos- 
phate. These figures are from |8 to $13 below the most favorable 
ones recorded for the production of a ton of P 2 O s by the electric- 
furnace and sulphuric acid methods. Whether or not efficiencies can 
be obtained through a more extended run commensurate with those 
indicated during these short periods must yet be proven, but certain 
fundamental principles have been established, and such progress has 
been made that it appears likely this general method of producing 
phosphoric acid will be commercially applied. 
