nacetin. Meta-aminophenol,
C6H4.OH.NH2(1.3), and dimethyl meta-aminophenol, C6H4.OH.N(CH3)2(1.3),
are extensively employed in the manufacture of the important dyestuffs
known as the rhodamines. The aminophenols also find application as
developers in photography, the more important of these developers
being amidol, the hydrochloride of diaminophenol, ortol, the
hydrochloride of para-methylaminophenol, C6H4.OH.NHCH3.HCl(1.4),
rodinal, para-aminophenol, and metol, the sulphate of a
methylaminophenol sulphonic acid. Meta-aminophenol is prepared by
reducing meta-nitrophenol, or by heating resorcin with ammonium
chloride and ammonia to 200 deg. C. Dimethyl-meta-aminophenol is
prepared by heating meta-aminophenol with methyl alcohol and
hydrochloric acid in an autoclave; by sulphonation of dimethylaniline,
the sulphonic acid formed being finally fused with potash; or by
nitrating dimethylaniline, in the presence of sulphuric, acid at 0
deg. C. In the latter case a mixture of nitro-compounds is obtained
which can be separated by the addition of sodium carbonate. The
meta-nitro-compound, which is precipitated last, is then reduced, and
the amino group so formed is replaced by the hydroxyl group by means
of the Sandmeyer reaction. Dimethyl-meta-aminophenol crystallizes in
small prisms which melt at 87 deg. C. It condenses with phthalic
anhydride to form rhodamine, and with succinic anhydride to rhodamine
S.

Phenol dissolves readily in concentrated sulphuric acid, a mixture of
phenol-ortho- and -para-sulphonic acids being formed. These acids may
be separated by conversion into their potassium salts, which are then
fractionally crystallized, the potassium salt of the para-acid
separating first. The ortho-acid, in the form of its aqueous solution,
is sometimes used as an antiseptic, under the name of aseptol. A
_thiophenol_, C6H5SH, is known, and is prepared by the action of
phosphorus pentasulphide on phenol, or by distilling a mixture of
sodium benzene sulphonate and potassium sulphydrate. It is a
colourless liquid, which possesses a very disagreeable smell, and
boils at 168 deg. C.

Various methods have been devised for the quantitative determination
of phenol. J. Messinger and G. Vortmann (_Ber._, 1890, 23, p. 2753)
dissolve phenol in caustic alkali, make the solution up to known
volume, take an aliquot part, warm it to 60 deg. C., and add
decinormal