These two bodies are
trioxyanthraquinones.
We call to mind that alizarin dyes reds of a violet tone, free from
yellow; roses with a blue cast and beautiful purples. Anthrapurpurin and
flavopurpurin differ little from each other, though the shades dyed
with the latter are more yellow. The reds produced with these coloring
matters have a very bright yellowish reflection, but the roses are too
yellow and the purples incline to a dull gray.
Experience with the madder colors shows that a mixture of alizarin and
purpurin yields the most beautiful roses in the steam style, but it is
not the same in dyeing, where the roses got with fleur de garance have
never been equaled.
"Alizarins for reds" all contain more or less of alizarin properly
so-called, from 1 to 10 per cent., along with anthrapurpurin and
flavopurpurin. This proportion does not affect the tone of the reds
obtained further than by preventing them by having too yellow a tone.
The first use of the alizarins for reds was for application of styles,
that is colors containing at once the mordant and the coloring matter
and fixed upon the cloth by the action of steam. Good steam-reds were
easily obtained by using receipts originally designed for extracts of
madder (mixtures of alizarin and purpurin). On the other hand, the first
attempts at dyeing red grounds and red pieces were not successful. The
custom of dyeing up to a brown with fleur and then lightening the shade
by a succession of soapings and cleanings had much to do with this
failure.
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