The natural (laevo) base is twice as toxic as the dextro.
The inactive mixture may be resolved into its active components by fractional crystallization of the cinchonine salt, when the salt of the dextro modification separates first; or the ammonium salt may be fermented by Penicillium glaucum, when the laevo form is destroyed and the dextro form remains untouched; on the other' hand, Saccharomyces ellipsoideus destroys the dextro form, but does not touch the laevo form.
It was surmised that a-acrose was a mixture of dextro and laevo fructose, a supposition which was proved correct by an indirect method.
Also Kiliani found that the lactone derived from the cyanhydrin of natural arabinose (laevo) was identical with the previous lactone except that its rotation was equal and opposite.
Similarly the 1 acid yields the laevo derivatives.