Dissolve 10 grammes in HCl, filter into a flask, wash the residue well,
neutralize with ammonia and Na,CO, and add a little Na^S^Oj. When
the color has passed through violet to colorless, add 2 or 3 c.c. of satu-
rated solution of NajHPO^ and 5 or 6 grammes NaCgHjO,. Boil until
there is no odor of SO,. Filter and wash. Dissolve the precipitate
with HCl, evaporate to dryness to separate SiO,. Take up with HCl,
filter and treat the solution as before, using about 2 grammes Na.^Sj08,
and 2 grammes NaCjH^O^. Weigh the last precipitate Al, (PO^^^ and
calculate.
Commercial Aluminum, Regelberger (Zts. Angew. Chem.^ No. i,
1891) finds that the determination of Al by methods based on the pro-
portion of H evolved by dissolving in KOH, gives incorrect results.
The methods by determining impurities present he regards as better.
For a direct determination 2 gms. of the sample are dissolved by the
acid of 15 gms. pure KOH, in a platinum dish, and the solution made
up to 200 c.c. In 50 c.c. Al/OH), is precipitated by boiling with a
slight excess of NH^NO,. The precipitate should be tested for SiO
after ignition. The impurities in the KOH used must also be allowed
for.
VOL. XII.— 18



262 THE QUARTERLY.
Estimating Titanium Colorimetrically, Noyes {Jour, Anal, Chem.j v.,
39). Mix 0.1 gm. of the finely powdered mineral with 0.2 gm. pow-
dered NaF. Add 3 gms. sodium pyrosulphate. Fuse carefully, holding
the burner in the hand, until copious fumes escape (2 or 3 minutes).
