--_La Nature._
[Illustration: Fig. 4.--DETAILS OF THE RECEIVER.]
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NOTES ON DYEWOOD EXTRACTS AND SIMILAR PREPARATIONS.
By LOUIS SIEBOLD, F.I.C., F.C.S.
During the last ten years there has been an enormous increase in the
production of these preparations, and the time will come when their
application in dyeing and calico printing will become so general as to
completely supersede the employment of the raw materials. The
manufacture of these extracts, to be thoroughly successful, requires
to be so conducted as to secure the perfect exhaustion of the dyewoods
without the slightest destruction or deterioration of the coloring
matters contained in them; and though nothing like perfection has been
reached in the attainment of these objects, it is certain that the
processes of extraction and evaporation now employed by the best
makers are a very great improvement on the older methods. Indeed,
there is no difficulty nowadays in procuring dyewood extracts of high
excellence if the consumer is willing to pay a price for them
corresponding to their quality, and knows how to avail himself of the
aid of chemical skill to control his purchases. Unfortunately,
however, there is so much hankering after cheap articles, and so
little care is taken to ascertain their real quality, that every scope
is afforded to the malpractices of the adulterer.
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