[1] Published by them in the _Amherst Papyri_, an account of the
Greek papyri in the collection of Lord Amherst (1900), and by Charles
in his edition.
ISANDHLWANA, an isolated hill in Zululand, 8 m. S.E. of Rorke's Drift
across the Tugela river, and 105 m. N. by W. of Durban. On the 22nd of
January 1879 a British force encamped at the foot of the hill was
attacked by about 10,000 Zulus, the flower of Cetewayo's army, and
destroyed. Of eight hundred Europeans engaged about forty escaped (see
ZULULAND: _History_).
ISAR (identical with _Isere_, in Celtic "the rapid"), a river of
Bavaria. It rises in the Tirolese Alps N.E. from Innsbruck, at an
altitude of 5840 ft. It first winds in deep, narrow glens and gorges
through the Alps, and at Tolz (2100 ft.), due north from its source,
enters the Bavarian plain, which it traverses in a generally north and
north-east direction, and pours its waters into the Danube immediately
below Deggendorf after a course of 219 m. The area of its drainage basin
is 38,200 sq. m. Below Munich the stream is 140 to 350 yards wide, and
is studded with islands. It is not navigable, except for rafts. The
total fall of the river is 4816 ft. The Isar is essentially the national
stream of the Bavarians. It has belonged from the earliest times to the
Bavarian people and traverses the finest corn land in the kingdom. On
its banks lie the cities of Munich and Landshut, and the venerable
episcopal see of Freising, and the inhabitants of the district it waters
are reckoned the core of the Bavarian race.
See C. Gruber, _Die Isar nach ihrer Entwickelung und ihren
hydrologischen Verhaltnissen_ (Munich, 1889); and _Die Bedeutung der
Isar als Verkehrsstrasse_ (Munich, 1890).
ISATIN, C8H5NO2, in chemistry, a derivative of indol, interesting on
account of its relation to indigo; it may be regarded as the anhydride
of ortho-aminobenzoylformic or isatinic acid. It crystallizes in orange
red prisms which melt at 200-201 deg. C. It may be prepared by oxidizing
indigo with nitric or chromic acid (O. L. Erdmann, _Jour. prak. Chem._,
1841, 24, p. 11); by boiling ortho-nitrophenylpropiolic acid with
alkalis (A. Baeyer, _Ber._, 1880, 13, p. 2259), or by oxidizing
carbostyril with alkaline potassium permanganate (P. Friedlander and H.
Ostermaier, _Ber._, 1881, 14, p. 1921). P. J. Meyer (German Patent 26736
(1883)) obtains substituted isatins by condensing para-toluidine with
dichloracetic acid, oxidizing the product with air and then hydrolysing
the oxidized product with hydrochloric acid. T. Sandmeyer (German
Patents 113981 and 119831 (1899)) obtained isatin-[alpha]-anilide by
condensing aniline with chloral hydrate and hydroxylamine, an
intermediate product isonitrosodiphenylacetamidine being obtained, which
is converted into isatin-[alpha]-anilide by sulphuric acid. This can be
converted into indigo by reduction with ammonium sulphide. Isatin
dissolved in concentrated sulphuric acid gives a blue coloration with
thiophene, due to the formation of indophenin (see _Abst. J.C.S._,
1907). Concentrated nitric acid oxidizes it to oxalic acid, and alkali
fusion yields aniline. It dissolves in soda forming a violet solution,
which soon becomes yellow, a change due to the transformation of sodium
N-isatin into sodium isatate, the _aci_-isatin salt being probably
formed intermediately (Heller, _Abst. J.C.S._, 1907, i. p. 442). Most
metallic salts are N-derivatives yielding N-methyl ethers; the silver
salt is, however, an O-derivative, yielding an O-methyl ether (A. v.
Baeyer, 1883; W. Peters, _Abst. J.C.S._, 1907, i. p. 239).
/\ /CO /\ /CO /\ /CO /\ /CO
/ \ / \ / \ / \ / \ / \ / \ / \
| | \CO | | \CO | | \ | | \
| | / | | / | | //C(OH) | | //COAg.
\ / \ / \ / \ / \ / \ // \ / \ //
\/ \NH \/ \N(Na) \/ \N \/ \N