OCR Text |
Show SPEARMINT. stances. On the other hand, some of the disagreeable strongscented plants, as wormwood, are said to contain most oil in rainy seasons, and when growing in moist rich grounds. Several chemists have been of opinion, that herbs and flowers, moderately dried, yield a greater quantity of volatile oil than if they were distilled when fresh. It is, however, highly improbable that the quantity of volatile oil will be increased by drying; on the contrary, part of it must be dissipated and lost. But drying may sometimes be useful in other ways, either by diminishing the bulk of the subject to bedistilled, or by causingit to part with its oil more easily. The choice of proper instrumentsis of great consequence for be added as will fill two-thirds of it. When fresh and juicy herbs are to bedistilled, thrice their weight of water will befully sufficient; but dry ones require a much larger quantity. In general, there should be so much water, that, after all intended to be distilled has come over, there maybe liquor enough left to prevent the matter from burning to the still. The water and ingredients, altogether, should never take up more than threefourths of the still; there should be liquor enough to prevent any danger of any empyreuma, but not so muchasto be apt to boil over into the receiver. The subject of distillation should be macerated in the water until it be perfectly penetrated by it. To promote this effect, woods should be thinly shaved across the grain, or sawn, roots cut transversely into thin slices, barks reduced into coarse pow- der, and seeds slightly bruised. Very compact and tenacious substances require the maceration to be continued a week or two, or longer; for those of a softer and looser texture, two or three days are sufficient; while some tender herbs and flowers not only stand in no need of maceration, but are even injured large low head, having a rim or hollow canal roundit: in this by it. The fermentation which was formerly prescribed in some instances, is always hurtful. The fire ought to be quickly raised, aud kept up during the whole process, but to such a degree only that the oil mayfreely distil; otherwise the oil will be exposed to an unnecessary heat ; a circumstance which ought, as much as possible, to be avoided. canal the oil is detainedin its first ascent, and thence conveyed Fire communicates to all these oils a disagreeable impregnation, at once into the receiver, the advantages of whichare sufficiently obvious. We cannot separate the volatile oils from aromatic substances by distilling them alone, because the proportion of theseoils is so small that they could not be collected; and besides, it would be impossible to regulate the heat so as to be sufficient, and yet not to burn the subject, and destroy the product. Henceit is tion it produces in them. the performance of this process to advantage. ‘There are some oils which pass freely over the swan-neck of the head of the common still: others, less volatile, cannot easily be made to rise so high. For obtaining these last, we would recommend a necessary to distil them with a proportion of water, which answers extremely well, as the oils are all more volatile in water, and soluble in it only to a certain extent. With regard to the proportion of water to be employed; if as is evident from their being much less grateful when newly distilled than after they have stood for some time in a cool Place ; and the longer the heat is continued, the greater alteraThe greater number of oils require for their distillation the heat of water strongly boiling: but there are many also which tise with a heat considerably less; such as those of lemon and citron peel, of the flowers of lavender and rosemary, and of almost all the more odoriferous kinds of flowers, We havealready observed, that these flowers have their fragrance much injured, or even destroyed, by beating or bruising them; it is impaired also by the immersion in waterin the present process, aes in dry soils and in warm summers, than in opposite cir¢um- pressed, will occupy half its cavity ; and as much water may é fragrant herbsyield a larger proportion of oil, when produced whole plants, moderately dried, are used, or the shavings of woods, as muchof either may be put into the vessel as, lightly Be quantity when young, before they have sent forth any flowers; andothers, as thyme, whenthe flowers have just appeared. All 565 ae are submitted to the operation at once; while savin, whose dis. agreeable scent extends to no great distance, gives out the largest proportion of volatile oil of almost any vegetable known. Nor are the same plants equally fit for this operation, when produced in different soils or seasons, or at different times of their growth. Some yield more oil if gathered whenthe flowers begin to fall off than at any other time. Of this we have ex. amples in lavender and rue; others, as sage, afford the largest SPEARMINT. ee oe 564 |