m carbonate in 400 c.c. of water. After
cooling, the clear liquid is decanted, the remainder filtered, and the
filtrate made up to a litre; to each litre is added 25 c.c. of sodium
hydroxide solution (sp. gr. 1.29).

(5.) An aqueous solution of the acetone, containing 1 or 2 per cent. of
acetone.

(6.) Bicarbonated starch solution prepared by treating 0.125 grm. of
starch with 5 c.c. of cold water, then adding 20 c.c. of boiling water,
boiling a few minutes, cooling, and adding 2 grms. of sodium bicarbonate.

To 20 c.c. of the potassium iodide solution are added 10 c.c. of the
diluted aqueous acetone, an excess of the sodium hypochlorite solution is
then run in from a burette and well shaken for a minute. The mixture is
then acidified with the hydrochloric acid solution, and while agitated, an
excess of sodium thiosulphate solution is added, the mixture being
afterwards allowed to stand a few minutes. The starch indicator is then
added, and the excess of thiosulphate re-titrated. The relation of the
sodium hypochlorite solution to the sodium thiosulphate being known, the
percentage of acetone can be readily calculated.[A]

[Footnote A: See "The Testing of Acetone," Conroy, _Jour. Soc. Chem.
Ind._, 31st March 1900, vol. xix.]

Dr S.J.M. Auld has recently (_Jour. Chem. Soc._, Feb. 15, 1906, vol. xxv.)
worked out a volumetric method for the estimation of acetone, depending on
the formation of bromoform, and its subsequent hydrolysis with alcoholic
potash. The hydrolysis is probably expressed thus--

3CHBr_{3} + 9KOH + C_{2}H_{5}OH = 3CO + C_{2}H_{4} + 9KBr + 7H_{2}O

as it has been shown by Hermann and Long that exactly 3 volumes of carbon
monoxide to 1 of ethylene are evolved. The residual potassium bromide is
estimated by means of standard silver nitrate solution. Bromoform is
specially suitable for this purpose for several reasons. It is very
readily formed by the action of bromine and potash on acetone, and
although very volatile in steam, it is not liable to loss due to its own
evaporation. Further, its high molecular weight and large percentage of
bromine conduce to accurate results, 58 grms. of acetone being responsible
for the formation of 357 grms. of KBr. The method of carrying out the
analysis is as follows:--

A known quantity of the solution to be tested, containing acetone to the
extent of 0.1 to 0.2 grm., is pipetted into a 500 c.c. round-bottom flask,
diluted with a little water, and mixed with 20 t