gravity at 60 deg. F. When
mixed with distilled water it must show no turbidity, and must leave no
residue on evaporation at 212 deg. F. On distillation, four-fifths by volume
of the quantity taken must distil over at a temperature not exceeding 138 deg.
F. The residual matter left after this distillation must not contain,
besides acetone, any ingredient that is not a bye-product incidental to
the manufacture of acetone.

2. One c.c. of 0.10 per cent. solution in distilled water of pure
permanganate of potash, added to 100 c.c. of the acetone, must retain its
distinctive colour for not less than 30 minutes. This test should be made
at a temperature of 60 deg. F.

3. The acetone tested by the following method must not show more than
0.005 per cent. of acid, calculated to acetic acid:--

To 50 c.c. of the sample diluted with 50 c.c. of distilled water, with 2
c.c. of phenol-phthalein solution (1 gramme to 1,000 c.c. of 50 per cent.
alcohol) added as an indicator, add from a burette N/100 sodium hydrate
solution (1 c.c. 0.0006 gramme acetic acid), and calculate to acetic acid
in the usual manner.

The water used for the dilution of the acetone must be carefully tested
for acidity, and the pipettes used for measuring should not be blown out,
as it would be possible thus to neutralise nearly 2 c.c. of the soda
solution.

The presence of water in a sample of acetone may be detected by Schweitzer
and Lungwitz's method (_Chem. Zeit._, 1895, xix., p. 1384), which consists
in shaking together equal volumes of acetone and petroleum ether (boiling
point, 40 deg. to 60 deg. C.), when if present a separation of the liquid in
layers will take place.

~Estimation of Acetone.~--Kebler (_Jour. Amer. Chem. Soc._, 1897, 19, 316-
320) has improved Squibb's modification of Robineau and Rollins' method.
The following solutions are required:--

(1.) A 6 per cent. solution of hydrochloric acid.

(2.) A decinormal solution of sodium thiosulphate.

(3.) Alkaline potassium iodide solution prepared by dissolving 250 grms.
of potassium iodide in water, made up to a litre; dissolving 257 grms. of
sodium hydroxide (by alcohol) in water, likewise made up to a litre. After
allowing the latter to stand, 800 c.c. of the clear solution are added to
the litre of KI.

(4.) Sodium hypochlorite solution: 100 grms. of bleaching powder (35 per
cent.) are mixed with 400 c.c. of water: to this is added a hot solution
of 120 grms. of crystallised sodiu