§ 94. QUANTITATIVE METHODS. 163 



III. 



NO ALUMINA IS PRESENT, AND PHOSPnORIC ACID IS IN EXCESS OVER 



THE IRON. 



Divide tlic filtrate from tlie silica in two parts, a and b. 



a. I b. 



Determine 1. Add an acearately titrated solution of Fe^Clfl, nearly' 

 SO3, FaOsjK,! neutralize the solution with NasCOa, precipitate Fe and 

 P2O5 with NaCsHgOQ (A); dissolve the precipitate in HCl, 

 divide solution in two equal portions, a and (i. 



and Na, as 



under a, 



Scheme I. 



3 a. 

 Determine Fe with per- 

 manganate (A.) 



2[i. 

 Determine P2O5 with (NH4)2- 

 M0O3 (H, 1) or citric acid and 

 mati'nesia mixture (H, 2). 



3. Determine Mn, Ca, and Mg, in the filtrate from the 

 precipitate by NaC2H302, as in 3, 3, and 4, under c, 

 Scheme I. 



IV. 



NO ALUMINA OR MANGANESE IS PRESENT, AND PHOSPHORIC ACID IS IN 

 EXCESS OVER THE IRON. 



Proceed as in III, except that the elimination of manganese by chlorine 

 may be omitted. 



TO DETERMINE ALL WITHOUT DIVIDING THE SOLUTION. 



1. To the filtrate from the silica add the titrated solution of ferric 

 chloride, if necessary, (see § 93, A, 2), nearly neutralize the solution with 

 (NH4)2C03, precipitate Fe, Al, and P2O5, with NH4C2H3O2, dissolve the 

 precipitate in HCl, and divide the solution in two equal portions ; pre- 

 cipitate one portion with NH4HO, and get total Al, Fe, and PoOg; heat 

 the ignited residue in a mixture of 8 parts of concentrated sulphuric 

 acid and 3 parts of water, add water, and determine Fe in this solution 

 with potassic permanganate (A) ; eliminate P2O5 in the other portion of 

 the solution, with the aid of ammonic molybdate, or magnesia mixture 

 in the presence of citric acid. (H.) 



2. First Filtrate. {From the precip. by NHiCJIz02.) Evaporate 

 to dryness and ignite the residue until ammonic salts are completely ex- 

 pelled; dissolve in water acidified with HCl, nearly neutralize the solu- 

 tion with NaaCOa, add NaCaHgOj, and precipitate Mu by CI. (C.) 



3. Second Filtrate. {From (he jirecipitate by CI) After removing 

 excess of CI by heat, precipitate Ca with (NH4)2C204. (D.) 



4. Third Filtrate. {From the precip. by {NHi^C^Oi). Precipitate 

 SOgwithBaCl. (E.) 



