 | OH | |
| Thymol, C₆H₃ | CH₃, as contained in Thymus vulgaris. | |
| C₃H₇ |
We obtained it by exposing oil of our own distillation, first rectified from chloride of calcium, to a temperature of 0° C., when the oil deposited 36 per cent. of thymol in superb tabular crystals, an inch or more in length. The liquid portion, even after long exposure to a cold some degrees below the freezing point, yielded no further crop. We found the thymol thus obtained began to melt at 44° C., yet using somewhat larger quantities, it appeared to require fully 51° C. for complete fusion. On cooling, it continues fluid for a long time, and only recrystallizes when a crystal of thymol is projected into it.
Thymol is more conveniently and completely extracted from the oil by shaking it repeatedly with caustic lye, and neutralizing the latter.
The oil of ajowan, from which the thymol has been removed, boils at about 172°, and contains cymene (or cymol), C₁₀H₁₄, which, with concentrated sulphuric acid, affords cymen-sulphonic acid, C₁₀H₁₃SO₂OH. The latter is not very readily crystallizable, but forms crystallized salts with baryum, calcium, zinc, lead, which are abundantly soluble in water. In the oil of ajowan no constituent of the formula C₁₀H₁₆ appears to be present; mixed with alcohol and nitric acid ([see p. 279]) it at least produces no crystals of terpin.
The residual portions of the oil, from which the cymene has been distilled, contains another substance of the phenol class different from thymol.
We have found that neither the thymol nor the liquid part of ajowan oil possesses any rotatory power.
Uses—Ajowan is much used by the natives of India as a condiment.[1157] The distilled water which has been introduced into the Pharmacopœia of India, is reputed to be carminative, and a good vehicle for nauseous medicines. It has a powerful burning taste, and would seem to require dilution. The volatile oil may be used in the place of oil of thyme, which it closely resembles.
Ajowan seeds are largely imported into Europe since thymol has been universally introduced into medical practice (see Folia Thymi). They have proved much more remunerative for the manufacture of thymol than Thymus vulgaris. The largest quantities, we believe, of thymol have been made from ajowan at Leipzig.
Substitutes—Under the name Semen Ammi, the very small fruits of Ammi majus L. and of Sison Amomum L. have been often confounded with those of Ajowan; but the absence of hairs on the two former, not to mention some other differences, is sufficient to negative any supposition of identity.
The seeds of Hyoscyamus niger L. being called in India Khorāsāniajwān, a confusion might arise between them and true ajowan; though the slightest examination would suffice to show the difference.[1158]