A Manual of the Chemistry of the Carbon Compounds

TEE CARBON COMPOUNDS. 461
Concentrated nitric acid converts it into diuitro-arbutin, which by
boiling dilute sulphuric acid is resolved into glucose and dinitrohydroquinone.
Phlorizin CS,H?4O1O + 2H2O occurs in the root-bark of the apple,
pear, plum, and cherry-tree, and is obtained by exhausting the bark
with hot dilute alcohol. It crystallizes from boiling water in silky
needles, possessing a bitter taste. On heating it loses water and melts
at 108". On boiling it with dilute acids it splits up into glucose and
phloretin:—
O2lH2Ao + 2 H8O = CoH12Oa + C1SH14O8
Phloretin C,5Hn0a forms crystalline scales; boiling alkalis decompose
it into phloretic acid C.H4(OH)C8H6O2 (page 395) and phloroglucin
CaH3(0H). (page 344).
Phlorizin has therefore the following constitution:—
C0Hx,O61 o
C8H4(0H)C2H4.COj o
JEsculin CaH24Olg exists in the bark of the horse-chestnut and
other trees of the genera dSsculus and Pavia. It is sparingly soluble
in cold and more freely in hot water, and crystallizes in colourless
needles having a bitter taste. Its aqueous solution, even if very
dilute, exhibits a beautiful sky-blue fluorescence. By boiling dilate
acids or emnlsin it is decomposed into glucose and tesculetin:—•
02iH84O13 + 3H4O = 2C8H12O6 + C9HaO4
uEseuldin C9Hg0t is also found in the free state in the bark of the
horse-chestnut. It is sparingly soluble in water, and forms needles
having a bitter taste. Boiliug potash decomposes it into formic acid,
oxalic acid, and protocatechuic acid CjHjtOH^COgH.
Qwrcztrin CgjH^Oj is the colouring matter of " quercitron " (the
bark of Querctis tinctoria), and occurs also in the flowers of the horsechestnut.
It is sparingly soluble in water, and forms small yellow
crystals. By boiling it with dilute sulphuric acid it yields isodulcite
(page 280) and guercetin.
Qitercelin, or Flavin C^HjoO^, exists also in the free state in the
common heather, in tea, ana the root-bark of several trees. It is
sparingly soluble in water, and sublimes in yellow needles. When it
is heated with caustic potash different products are formed, among
•which have been found phloroglucin, protocatechuic acid, and quercimerie
acid CH^(OH)(COjH)., which crystallizes in thick prisms, and
gives with ferric chloride a bluish-black colour.
The following compounds have great resemblance to queroitrin;
they yield as products of decomposition quercetin and peculiar