These views are suggested
as a result of a careful application of the original Le Bel-Van't Hoff
hypothesis, and are, of course, of little value unless they can be shown
to be in accordance with the facts.
The chief merit of the work of Wislicenus consists in the fact that he
has shown that a large number of phenomena which have been observed in
the study of such cases of isomerism as were mentioned above find a
ready explanation in terms of the new hypothesis, whereas for most of
these phenomena no explanation whatever has thus far been presented. The
most marked case presented is that of maleic and fumaric acids. One by
one, the author discusses the transformations of these acids and their
substitution products, and becomes to this conclusion: "There is not to
my knowledge a single fact known in regard to the relations between
fumaric and maleic acids which is not explained by the aid of the above
geometrical considerations, not one which does not clearly support the
new hypothesis." Among the facts which he discusses in the light of the
hypothesis are these: The formation of fumaric and maleic acids from
malic acid; the quantitative transformation of maleic into fumaric acid
by contact with strong acids; the transformation of the ethereal salts
of maleic acid into those of fumaric acid by the action of a minute
quantity of free iodine; the formation of brommaleic acid and
hydrobromic acid from the dibromsuccinic acid formed by the addition of
two bromine atoms to fumaric acid; the formation of dibromsuccinic acid
from brommaleic acid and of isodibromsuccinic acid from bromfumaric acid
by the action of fuming hydrobromic acid; the conversion of brommaleic
acid into fumaric and then into succinic acid by the action of sodium
amalgam; the formation of one and the same tribromsuccinic acid by the
action of bromine on brommaleic and on bromfumaric acid; and finally,
the conversion of maleic into inactive tartaric acid, and of fumaric
into racemic acid by potassium permanganate.
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