134 The Phosphates of America. 



Since, as we have already explained, the great bulk of our super- 

 phosphate is not made to contain more than from twelve to four- 

 teen per cent, of phosphoric acid soluble in water and ammonium 

 citrate, and since it, for this reason, only represents on an average the 

 equivalent of thirty per cent, of bone phosphate of lime made solu- 

 ble, it necessarily follows that more than three tons of it would be 

 required to equal one ton of the concentrated or high-grade ma- 

 terial. The latter contains the equivalent of ninety-nine percent, 

 of bone phosphate of lime, made practically as soluble and equally 

 available, and is therefore, as we have said, specially adapted to the 

 requirements of the middleman. The distributer would only pay 

 freight on one ton where he now pays it on three, and could, if he 

 so desired, dilute it down to the ordinary commercial strength by 

 the addition of gypsum, or any other convenient and low-priced 

 filler. 



A fruitful subject for angry discussion and costly litigation has 

 been that bearing on the noxious vapors evolved during the manu- 

 facture of fertilizers from any of the phosphates we have described. 

 It has been urged, and, to our minds, very consistently, that we 

 should apply to them the same methods so successfully used in 

 suppressing the devastating fumes from other chemical works, 

 and there cannot be a doubt that if this were done, the present 

 menace to the heaith and comfort of the workmen, and others 

 employed in and about the neighborhood, would disappear. 



As we have already pointed out, the fumes of fertilizer fac- 

 tories chiefly consist of carbonic acid, hydrofluoric acid, silicic 

 tetrafluoride, sulphuric acid and steam ; and of all these, the most 

 dangerous to life and health are the compounds generated by the 

 liberation of fluorine from the fluoride of calcium, the average pro- 

 portion of which in our phosphates may be safely taken at about 

 three per cent. The quantity of deadly vapor thus becomes very 

 large in some of our big works, but it need not necessarily be alarm- 

 ing provided the gas-flues be properly worked. A ventilating-fan 

 would easily conduct it all into the scrubber, where, meeting with a 

 fine spray of very cold water, it would immediately be decomposed, 

 hydrofluosilicic acid and gelatinous silica being formed. The acid 

 could either be washed away into the main sewers or passed off into 

 an open drain, and the finely divided silica could be allowed to de- 

 posit itself on the bottom of the condenser. 



Mr. John Morrison, an English chemical engineer of great abil- 

 ity, who has done a great deal of valuable work in this connection 



