MANJIT (INDIAN MADDER).
The roots of the East Indian _Rubia mungista_ contain purpurin and
another characteristic colouring matter, manjistin. This material is
a rarity in German commerce, but is imported into England from India
in tolerable amount and used in dyeing. Manjistin may be extracted
by boiling manjit repeatedly with a solution of aluminium sulphate,
uniting the liquids and acidifying strongly with hydrochloric acid. In
twenty-four hours a red precipitate forms in the liquid; it is dried
and treated with boiling carbon disulphide, which extracts purpurin
and manjistin and leaves undissolved a dark resin. The residue, after
distilling off the carbon bisulphide, gives up purpurin to dilute
acetic acid, manjistin remaining undissolved. When the purpurin has
been completely extracted, the residue is treated with a little boiling
alcohol and repeatedly recrystallised; manjistin is finally obtained in
golden yellow crystals of the composition C₁₄H₁₅O₂(OH)₂.CO₂H.
When a solution of manjistin in a little alcohol is mixed with water no
precipitate occurs; on then adding aluminium hydrate and long boiling
an orange red lake is produced. Lead acetate produces a deep orange red
lake when used in just sufficient quantity; with excess a fine scarlet
lake is obtained.
If manjit were a common article in the German market, it would be used
in the preparation of fine pigments with as much advantage as madder
and the various madder preparations.
=Chica Red, Curucuru, Carajuru.=—The colouring matter known under
these names rarely comes into commerce; it forms brownish-red masses
which acquire a peculiar golden glitter on rubbing. It is obtained
from the leaves of _Bignonia chica_, a native of tropical America. The
leaves are superficially dried and then covered with water; in the
warm climate the macerated leaves soon ferment, and a deep red powder
separates at the bottom of the vessel: this is the colouring matter; it
is dried, made into small cakes and brought into the market.
Chica red is only partially soluble in strong alcohol, the residue
chiefly consists of plant cells. Alum and stannous chloride precipitate
beautiful red lakes from the solution, which are distinguished by great
permanence when exposed to light. On account of the present high price,
this colouring matter has not yet obtained admission into the colour
industries, though it would be a valuable recruit.
Chica red has been little studied; an investigation would certainly
considerably increase our knowledge of the organic colouring matters.
Towards reducing agents it behaves in a similar manner to indigo; in
contact with caustic soda, grape sugar and water in closed flasks, a
violet liquid is produced; when exposed in an open vessel the violet at
once changes to brown, but if the liquid is syphoned off into dilute
hydrochloric acid a pure red precipitate separates, which is to be
regarded as the pure colouring matter.