Volume 1

The chemical works of Caspar Neumann ... / abridged and methodized. With large additions, containing the later discoveries and improvements made in chemistry and the arts depending thereon by William Lewis.

  • Caspar Neumann
Date:
1773
Catalogue details

Licence: Public Domain Mark

Credit: The chemical works of Caspar Neumann ... / abridged and methodized. With large additions, containing the later discoveries and improvements made in chemistry and the arts depending thereon by William Lewis. Source: Wellcome Collection.

    451/464 page 431
    extricated and communicated to the diftilled liquor : Essen- Veronica, a plant of very little ftnell, and which, if tial immediately committed to difbillation gives over no- Oils. thing confiderable, yields, if (lightly fermented, a Water that fmells and taftes ftrongly of the herb. The quantity of Water made ufe of muft be propor¬ tioned to the nature of the fubjedt: whatever quan¬ tity is added, the difbillation muft be continued no longer than while the liquor proves fufticiently im¬ pregnated with the flavour of the ingredients. The virtues of many plants come over moft plentifully in the firft runnings; whilft thofe of others are more ftrongly locked up, and fcarce begin to arife till the diftillation has been continued for fome time. Where the plant is of fuch a kind as to give but a weak impregnation to the diftilled Water; we may render the liquor ftronger by cohobation, that is, by draw¬ ing it over again from a frefti parcel of the fub- jed (j). Spirit (O Waters wade ftronger by cohobation.'] This is another of the many proceffes in which I have, on trial, been greatly difappointed. Though fome of the chemifts affirm, that diftilled Waters in general may be rendered, by repeated cohobations, of any aflignable degree of ftrength, and their virtues exalted without limitation-}-; I have not found that repetitions of thefe operations make any confiderable addi¬ tion to the ftrength even of thofe Waters, whofe exaltation by this treatment has been particularly fpecifted. The diftilled Waters of Mint, Rofemary, and other aromatic herbs, being rediftilled a number of times fucceffively from frefti parcels of the refpeftive fubjefls ; inftead of being more and more exalted and im¬ proved, they were on every repetition more and more debafed. Some of them indeed, by one cohobation, did feem to be rather mended, and fometimcs a fecond hid hardly any injury : but after this period, they all received an ungrateful taint from the repeated action of the fire, without gaining any more of the flavour of the fubjeft than they had at firft. It is not by diftillation, but by infufion, that Water can be unlimi¬ tedly impregnated with any of the principles of plants. Water extracts by infufion the gummy parts of vegetables ; and it is a property of all gummy lubftances to diiTolve indefinitely in Water, that is, to unite with any proportion of it, frnall or large, and render the liquor thicker •and thicker as the quantity of gummy matter is increafed. When Re¬ fins or effential Oils are intimately combined with gums, as they are in moft vegetables, thefe compounds unite alfo indefinitely with Water. -f Id, procefs xvi. Hence
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