142 SPECIAL METHODS OF ANALYSIS. 



to a corresponding quantity of F. 3, if there is no 

 F. 13, until a drop of the mixture gives a reddish 

 precipitate with ammonia. - - - - 19 



19. To the solution to which Fe^Clj has been added 

 (18), or to the remainder of the filtrate F. 13, if 

 no PqO^ was present in the substance, or to a cor- 

 responding quantity of F. 3, if there is no F. 13, 

 add ammonic carbonate until a slight permanent 

 precipitate remains after vigorous stirring ; if no 

 precipitate appears, the reagent may be added un- 

 til it is in slight excess, and the solution is faintly 

 alkaline. 



a. No ferric salt has been added to the solution, 

 and it remains quite clear, or only a fine white pre- 

 cipitate is formed after boiling it. - - - 20 

 h, AJlocculent precipitate is formed ; heat the so- 

 lution to boiling, add a boiling solution of sodic 

 acetate as long as a precipitate is formed, and fil- 

 ter the hot liquid immediately ; mark this filtrate 

 F. 19. - 2G 



20. a. Calcium has been found. - - - - 21 

 h. Not. To test for traces of the metal, add am- 

 monic sulphide to the filtrate from the precipitate 

 by sodic acetate, or, if this precipitation was not 

 found to be necessary in 19, to the liquid contain- 

 ing ammonic carbonate in slight excess, after acidi- 

 fication with acetic acid if not clear, filter out any 

 j^recipitate that may be formed, and add ammonic 

 chloride and oxalate to the filtrate ; a fine white 

 precipitate, insoluble in acetic acid, indicates Cal- 

 cium (traces). 21 



21. Add ammonic chloride and carbonate to F. 19, or 

 to the liquid already containing ammonic carbon- 

 ate in slight excess, and which gave no flocculent 

 precipitate with the reagent, boil the mixture, fil- 



