rilliant yellow pigments,
carotin and xanthophyll, and the reddish brown fucoxanthin and the
brilliant red lycopersicin, which are similar in their chemical
composition. The first two are found universally distributed in plants,
associated with the chlorophylls, and may be regarded as vegetative
pigments, although the characteristic ornamental yellow and orange colors
of many flowers and fruits, as well as that of the roots of carrots, etc.,
due to these pigments.

=Carotin.=--This pigment occurs in various forms in plants, both amorphous
and crystalline. It crystallizes out of solution in flat plates, which are
orange-red by transmitted light, and greenish-blue by reflected light, and
have a melting point of 168 deg. Carotin is insoluble in water, only very
slightly soluble in acetone or cold alcohol, readily soluble in petroleum
ether, ether, chloroform, and carbon disulfide. Its solutions are strongly
fluorescent.

Its molecular formula is C_{40}H_{56}. It is, therefore, a hydrocarbon of a
very high degree of unsaturation. On exposure to dry air, it absorbs 34.3
per cent of its own weight of oxygen, which corresponds to 111/2 atoms of
oxygen, computed on the basis of the molecular formula C_{40}H_{56}, and
would indicate a formula of (C_{40}H_{56})_{2}O_{23} for the oxygenated
compound; this being three oxygen atoms less than would be required to
bring the compound to the theoretical stage of saturation represented by
the unimolecular formula C_{_n_}H_{_2n+2_}. In moist air, two more oxygen
atoms are absorbed, probably forming two OH groups in the molecule.
Moreover, carotin absorbs iodine. When the calculated amount of iodine is
used, a definite compound having the formula C_{40}H_{56}I_{2} is produced;
but in the presence of an excess of iodine another compound having the
apparent formula C_{40}H_{56}I_{3} (or 2C_{40}H_{56}I_{2}+I_{2}) is
obtained. (Note that 2 atoms of iodine plus 12 atoms of oxygen, or 3 of
iodine plus 11 of oxygen, produce the degree of saturation required by
the formula C_{_n_}H_{_2n+2_}.) It is evident from these experimental data,
that a part of the unsaturated linkage in the carotin molecule is of a type
which can easily be saturated by direct addition of oxygen, while the
remainder may be saturated by iodine.

The reaction of carotin toward bromine is peculiar. With this element, it
forms a compound having the formula C_{40}H_{36}Br_{22}, indicating the
direct addition of two atoms of bro