The Phosphates of America. 163 



The results are always expressed in percentages of monohy- 

 drated sulphuric acid (H 2 SO 4 ) by weight. The specific gravity of 

 the acid is taken with a hydrometer and called x. Ten c.c. of the 

 acid are then taken with an accurate pipette and diluted to 100 c.o. 

 Of this solution 10 c.c. are taken for titration, and, if the number 

 of cubic centimetres of normal soda solution = 0.031 gramme Na 2 O 

 per cubic centimetre consumed is called y, the percentage of the 



acid is liy. 



RAPID ANALYSIS OF LIMESTONE OR CHALK. 



Insoluble. 



One gramme of the substance is dissolved in hydrochloric acid 

 and the residue is filtered, washed, dried, and ignited. In the presence 

 of appreciable quantities of organic substance the filter is weighed 

 after drying at 100, and afterwards ignited. The difference be- 

 tween the first and second weights is taken as organic matter. 



Lime. 



One gramme of the substance is dissolved in 25 c.c. normal hy- 

 drochloric acid and titrated with normal alkali. The amount of 

 alkali used is deducted from 25 and the remainder is multiplied by 

 2.8 to find the percentage of CaO, or by 5 to find that of CaCO 3 . 

 If any magnesia be present it would be calculated as lime, and 

 provided its amount be not very large, this is admissible in the 

 manufacture of "supers" on the plan we have suggested. 



When, however, the magnesia exceeds, say two per cent., it can 

 be separately estimated as follows, and the result deducted from the 

 figure given above. 



Magnesia. 



Two grammes of the substance are dissolved in HC1 ; the CaO 

 is precipitated with NH 3 and ammonium oxalate, and filtered with 

 the usual precautions. The magnesia is precipitated in the filtrate 

 by sodium phosphate, filtered, washed with ammonia water, dried, 

 ignited, *and weighed as Mg 2 P 2 O 7 , which X .3603 = MgO. 



Iron. 



Two grammes of the substance are dissolved in HC1, reduced 

 by zinc, and diluted. Some manganese solution free from iron is. 

 then added and the mixture is titrated with \ N. permanganate, of 

 which each c.c. = .0080 Fe 2 O 3 . 



