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198 QUANTITATIVE AGRICULTURAL ANALYSIS

Analytical chemistry has made little progress in this direction.
The application of delicate tests for metals (nickel, palladium,
etc.) that are used as catalyzers in the hardening process, may
sometimes serve to prove that the material is a hardened oil,
rather than a natural fat. Other than this one can say very little.
But the knowledge of the nature of the changes caused by hydro-
genation should serve to make the analyst more cautious than
he might otherwise be when interpreting the results of his
analytical data on oils or fats of unknown origin.
Interpretation of Analytical Data.—In the discussion of each
so-called "constant," in the foregoing pages it has been shown
that each determination will be of importance in the identifica-
tion of a certain limited number of oils, fats or waxes and that
f | in cases other than these the figures will give only negative
4 j! results. The materials for which such figures have proved to be
* ;'^ of significance were given in most of the discussions of these
^ /Ij/j \ determinations.
'''?] | In Table XII the various "constants" for a number of the more
1 "^ 'I common oils, fats and waxes are collated and the ones that are
of particular value in each case are printed in bold face type.
The iodine number will be of value in practically all cases, since
it is characteristic of classes, even when not of the individuals
of a given class.
Although only one value is given in each case, it should be remem-
bered that these are merely approximate averages and exact agree-
ment with experimental results should not be expected. Where
i || ; blanks occur in the table this is either because no value is on
record or because the figure is so low as to be practically negligible.
For additional special tests and for a complete description of
the individual oils, consult special treatises on the subject,
such as Lewkowitsch, "Chemical Technology and Analysis of
{If Oils, Fats and Waxes," and Fryer and Weston, "Oils, Fats and
* , Waxes."