52 PRACTICAL FAEM CHEMISTRY. 



percentage of phosphoric acid (P2O5) is contained 



in phosphate of lime (Ca3P208)? 

 Phosphate of lime consists of 

 Cas (three atoms of calcium @, 40 weight units) - 120 

 Pa (two atoms of phosphorus @ 31 weight units) - 62 



Os (eight atoms of oxygen @ 16 weight units) - 128 



Total, 310 



Phosphoric acid consists of 

 Pj (two atoms of phosphorus @, 31 weight units) - 62 

 Ofi (five atoms of oxygen @ 16 weight units) - - 80 



Total, 142 



Thus we find in every 810 weights of phosphate 

 of lime 142 weights of phosphoric acid, which is 

 equal to 45.80 per cent. 



End of First Part. 



