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 deg. F. (50 deg. C.) with the
addition of soap to the bath, dark shades at 200 deg. to 212 deg. F. (80 deg. to
100 deg. 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.
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