Mr. Greene's
zeal for experiment and depreciation of mental work would be in order,
if ways and means were to be found to render the advancement of science
as difficult and slow as possible; they are decidedly not in the
interest of science, and can not have been inspired by a desire for its
promotion.
As the evidence of the specific heats of the fallacy of Avogadro's
hypothesis involves lengthy explanations, the subject is reserved for
another paper.
San Francisco, Cal., May, 1881.
E. VOGEL.
* * * * *
DYEING REDS WITH ARTIFICIAL ALIZARIN.
By M. MAURICE PRUD'HOMME.
Since several years, the methods of madder dyeing have undergone a
complete revolution, the origin of which we will seek to point out. When
artificial alizarin, thanks to the beautiful researches of Graebe and
Liebermann, made its industrial appearance in 1869, it was soon found
that the commercial product, though yielding beautiful purples, was
incapable of producing brilliant reds (C. Koechlin). While admitting
that the new product was identical with the alizarin extracted from
madder, we were led to conclude that in order to produce fine Turkey
reds, the coloring matters which accompany alizarin must play an
important part. This was the idea propounded by Kuhlmann as far back as
1828 (_Soc. Ind. de Mulhouse_, 49, p. 86). According to the researches
of MM.
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