204] 



Method of Analysis 



129 



This will be found to simplify further calculations considerably. 

 The percentage so found may be calculated into P 2 5 by the 

 proportion 



Mol. wt. of Mg 2 P,0 7 : Mol. wt. of P 2 5 : : % of Mg 2 P 2 7 : % of P 2 5 . 

 From the percentage of P 2 5 so found that of the Ca 3 P 2 8 is 

 calculated. 



These calculations, and most others, are very much simplified 

 by using factors, of which a list is given in the appendix. 

 Thus, the percentage of Mg 2 P 2 7 x -64 = the percentage of 

 P 2 5 . To this the addition of '33 must be made, and the 

 result multiplied by 155 and divided by 71, or simply multiplied 

 by 2*1831, which gives the percentage of Ca 3 P 2 8 . In future 

 the simplest means of calculation is always given, and should 

 be verified by using the ordinary method. 



Lime. The substance weighed is CaC0 3 . Find the per- 

 centage and multiply by '56 ; this gives the percentage of CaO. 

 Subtract the P 2 5 from the Ca 3 P 2 8 . This gives the CaO 

 combined with the P 2 5 . To find the amount of CaO as 

 carbonate, subtract the amount combined with P 2 5 from the 

 total, and divide by -56. Should the C0 2 be determined 

 separately, the excess of CaO is entered as such. 



204. Mode of Entry : 



