Sulphuretted hydrogen, H2S, is frequently observed during the distillation of seeds, e. g. anise and particularly of caraway. Small amounts of carbon disulphide, CS2, are contained in the oil of black mustard. Both products presumably result as products of decomposition.
Dimethyl sulphide, (CH3)2S, b. p. 37°, has been found in American peppermint oil, also in Reunion and African oils of geranium.1) Traces of a mercaptan have been found in the oil of Allium ursinum, whereas the bulk of this oil consists of vinyl sulphide, (C2H3)2S, (b. p. 101°; d 0,9125) and its higher sulphides. Other unsaturated sulphides and polysulphides, among them presumably allyl disulphide, (C3H5)2S2, and allylpropy 1 disulphide, C3 H5 • C3 H7 • S2, occur together with other sulphur compounds in the oils of garlic, onion and asafetida.
All of these compounds are characterized by a most dis-agreable, penetrating odor. In the plants they are said to be contained in part, in combination as glucosides.
In this connection attention should be directed to Hartwich's2) list of plants in which the presence of sulphur-containing volatile oils has been demonstrated or inferred because of their odor.