These foreign substances are comprised in the term "unsaponifiable matter."
The most important constituents of the "unsaponifiable matter" are phytosterol C26H440 or C 27 H 44 0(?), and the isomeric cholesterol.
In the case of those oils which do not belong to the rape oils and yet show abnormally low saponification values, the suspicion is raised at once that a certain amount of mineral oils (which do not absorb alkali and are therefore termed "unsaponifiable") has been admixed fraudulently.
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