74 PRACTICAL ORGANIC CHEMISTRY

temperature of the thread of mercury outside the liquid, the
same formula being used as in the correction for the boiling-
point (see p. 58). When the acid becomes discoloured, a crystal
of potassium nitrate will remove the colour on warming.
Acetic Acid, CH3.CO.OH.
Commercial acetic acid is manufactured from pyroligneous
acid obtained in the destructive distillation of wood. The latter
is neutralised with lime, and separated by distillation from wood-
spirit and acetone. The crude calcium acetate, which has a
dark colour, is then distilled with the requisite quantity of con-
centrated hydrochloric acid. Anhydrous or glacial acetic acid
is obtained by distilling fused sodium acetate with concentrated
sulphuric acid.
Properties.—Colourless liquid with pungent smell ; b. p.
119°; m. p. 167°; sp. gr. 1*055 at 15°. It should not decolorise
a solution of permanganate. The vapour of the boiling acid is
inflammable.
Reactions.—Add a few drops of alcohol to the same quantity
of acetic acid, and an equal volume of concentrated sulphuric
acid. Warm gently and notice the fruity smell of ethyl acetate.
Neutralise a few drops of acetic acid by adding excess of
ammonia and boiling until neutral. Let cool and add a drop
of ferric chloride. The red colour of ferric acetate is produced,
On boiling, basic ferric acetate is precipitated.
Heat a very small quantity of potassium acetate with an equal
bulk of arsenious oxide. The disagreeable and poisonous vapour
of cacodyl oxide is evolved.
4CH3.COOK + As203=As«>(CH3)40 + 2CO, -f 2K2CO3.
PREPARATION 10.
Acetyl Chloride, CH3.CO.C1.
Gerhardt, Ann. Chim. Phys., 1853, (3) 37, 285 ; Bechamp
Compt. rend.) 1855, 40, 944, and 1856, 42, 224.
50 grms. glacial acetic acid.
40 „ phosphorus trichloride.
Fit up the apparatus shown in Fig. 54. It consists of a distilling
flask (250 c.c.), which is attached to a condenser. A small