Apr. 26, 1924 
Chemical Composition of Edible Viscera 
341 
weakly ammoniacal and boiled in order to precipitate the phosphates of the 
heavy metals and calcium. The filtrate and washings from this precipitate were 
then treated with a large excess of ammonia and allowed to stand over night to 
complete the precipitation of magnesium. The filtrate from the magnesium 
precipitate was reserved for the determination of the alkalies (Solution B), while 
the combined phosphate precipitates were dissolved in hydrochloric acid to form 
Solution C, which served for the determination of the heavy metals and the 
alkaline earths. 
Determination of iron .—When iron was determined, Solution C, was rendered 
slightly alkaline with ammonia, and the precipitate thus formed was redissolved 
by the careful addition of hydrochloric acid. Iron and aluminum phosphates were 
then precipitated by adding the appropriate quantity of ammonium acetate to 
the boiling solution. The precipitate thus obtained was filtered off, dissolved 
in acid, and reprecipitated in the same manner. The second precipitate was 
filtered off, washed, and dissolved in dilute acid, after which iron was deter¬ 
mined by reduction with metallic zinc and titration with decinormal permanga¬ 
nate. 
Determination of alkaline earths. —Solution C, or, where iron was determined, 
the combined filtrates from the iron determinations, were freed from interfering 
metals and from P 2 0 5 , and used for the determination of calcium and magnesium 
as described in the methods adopted by the Association of Official Agricultural 
Chemists for the determination of manganese, calcium, and magnesium in inor¬ 
ganic plant constituents ( 1 , p. 17), except that the calcium was estimated by 
titrating the calcium oxalate in sulphuric-acid solution with decinormal potas¬ 
sium permanganate. 
Determination of alkali metals. —Solution B, which served for the determination 
of the alkali metals, was brought to a volume of 250 cc. in a volumetric flask. 
A 100 cc. aliquot of this solution was transferred to a 200 cc. volumetric flask 
and rendered neutral to methyl red, after which it was treated with 4 cc. of 5 N 
ammonium acetate, 2 cc. of 5 N acetic acid, and a slight but definite excess of 
ferric chlorid. The solution was diluted to exactly 200 cc. and filtered through 
a dry, folded filter from the bulky precipitate of ferric phosphate. From 100 cc. 
of this filtrate, the excess iron was removed as the basic acetate by boiling and 
filtering; after which the new filtrate, combined with the washings, was treated 
with a few drops of dilute sulphuric acid and brought to dryness, the residue 
being ignited cautiously to expel the ammonium salts. The residue was then 
dissolved in a small quantity of water, treated with small quantities of ammo¬ 
nium hydroxid and ammonium carbonate, and the solution filtered into a weighed 
platinum dish. After evaporation the residue of sodium and potassium sulphate 
was brought to constant weight and weighed. Potassium was determined by 
-the Lindo-Gladding method ( 1, p. 12) and sodium by difference. 
In general, all determinations were made in duplicate and the average of closely 
agreeing duplicate determinations is reported. 
