in Central and Southern America. The red or orange colour it yields is
fugitive, and so its use is limited, being chiefly confined to silk
dyeing. The yellow compound it contains is called "Orellin," and it also
contains an orange compound called "Bixin," which is insoluble in water,
but readily soluble in alkalis and in alcohol with a deep yellow colour.
To dye cotton with it, a solution is made of the colour in a boiling
solution of carbonate of soda. The cotton is worked in the diluted
alkaline solution whilst hot. By passing the dyed cotton through water
acidulated with a little vitriol or alum, a redder tint is assumed. For
wool and silk, pale shades are dyed at 106° F. (50° C.) with the
addition of soap to the bath, dark shades at 200° to 212° F. (80° to
100° C.).




LECTURE X

DYESTUFFS AND COLOURS--_Continued_


_Artificial Substantive Dyestuffs._--You may remember that in the last
lecture we divided the colouring matters as follows: I. Substantive
colours, fixing themselves directly on animal fibres without a mordant,
only a few of them doing this, however, on vegetable fibres, like
cotton. We sub-divided them further as--(_a_) those occurring in nature,
and (_b_) those prepared artificially, and chiefly, but not entirely,
the coal-tar colouring matters. II. Adjective colours, fixing themselves
only in conjunction with a mordant or mordants on animal or vegetable
fibres, and including all the polygenetic colours. III. Mineral or