238 OXALATE AND PHOSPHATE OF LIME. 



then tightly adjusted, the orifice of the smaller tube 

 closed with wax, and the flask shaken so that the little 

 vessel may fill and sink. A volume of liquid equal 

 to that of the nitrogen evolved from the guano then 

 flows into the graduated cylinder ; when no more liquid 

 passes over, the cylinder is depressed so as to bring 

 the liquid to the same level as that in the generating- 

 flask ; the wax plug is then removed, the cork with- 

 drawn, and the liquid still contained in the delivery- 

 tube is allowed to run into the cylinder, where the 

 whole is carefully measured. 1 grm. of good guano 

 evolves between 70 and 80 cub. cents, of gas. 



120. OXALATE AND PHOSPHATE OF LIME. 



A mixture of these two salts dissolves in^nitric acid 

 without effervescence, and is precipitated from the 

 solution by ammonia. If it be digested, when freshly 

 precipitated, with acetic acid, the phosphate of lime 

 may be dissolved, while the oxalate is left. 



If the mixture be previouly ignited, it dissolves in 

 nitric acid with effervescence, and ammonia then pre- 

 cipitates from the solution only the phosphate of lime, 

 while the lime which had been in combination with 

 oxalic acid remains in solution, and may be precipitated 

 by oxalate of ammonia, and quantitatively determined. 

 Phosphate of lime, when freshly precipitated, may be 

 recognized by the yellow color which it assumes when 

 moistened on the filter, with nitrate of silver. It is 

 analyzed as in No. 13. 



If the two salts be dissolved in the smallest possible 

 quantity of hydrochloric acid, and the solution mixed 

 with an excess of acetate of soda, the oxalate of lime 

 is precipitated, while the phosphate remains in solu- 

 tion ; from the latter, the lime may be precipitated -by 



