The organic constituents of plants and vegetable substances and their chemical analysis / by G.C. Wittstein ; authorised translation from the German original, enlarged with numerous additions, by Baron Ferd. von Mueller.

  • Georg Christian Wittstein
Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: The organic constituents of plants and vegetable substances and their chemical analysis / by G.C. Wittstein ; authorised translation from the German original, enlarged with numerous additions, by Baron Ferd. von Mueller. Source: Wellcome Collection.

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    grams of it are required. The examination has to be conducted as indicated under Essential Oils, p. 77. (6) The aqueous distillate contains, besides small quantities of volatile oil, almost invariably some volatile organic acid, and has therefore an acid reaction. If the examination of these acids be required the distillate must not be treated with ether, as the lattei- removes both oil and acid. Test first on hydrocyanic acid, and employ in case of its pre- sence a weighed quantity of the distillate for its quantitative esti- mation. Both is done according to the in.struction given under '^Hydrocyanic acid, p. 107, Now mix the rest of the distillate with carbonate of bai-yta, rubbed down so as to form a fine milk, and evaporate on the water-bath, driving away together with the water any hydro- cyanic acid present. After the liquid has been reduced to 50 grams, filter off the excess of carbonate of baryta and evaporate slowly to dryness. As the residue will be very small it can only be exammed in regard to the more common volatile acids occurring in distillates, as formic acid, acetic acid, and as regards the lower members of the series of fat-acids, as propionic, butyric, valerianic acids, while a closer investigation is deferred to section IX. After the distillation has been finished, remove the tube con- ducting the steam, the head and the false bottom of the still, place the latter on the balance and determine the weight of the watei- by subtracting from the whole weight the weight of the still and of the raw material employed, add as much pure water as to make the whole up to twice the quantity of tlae raw material, add alcohol of 90%, equal in weight to the whole of the water, mix the whole assiduously with a spatula of beech-wood, replace the still once more into the hot water of the boiler, refit the head and con- tinue firing for the rest of the day—the distillation ought to be commenced in the morning—but not so strong as to make the alcohol pass over. After the apparatus has been left undisturbed for one day, the contents are strained, preferably, by means of a strong linen bag-filter, fastened to a tenacle, under assiduously stir- ring the mass in the filter with a spatula. After dripping has ceased, submit the remnant to the strongest possible pressure, put back into the still, mix with alcohol of 45% to a pulp, strain, press and repeat the same operation once more. Clarify the united alcoholic liquids by subsiding and filtering, distil ofi the alcohol completely in the tin still, remove the head and allow the contents of the still to cool down as slowly as possible, in order to remove the last traces of alcohol (for this ]>urpose the still is left suspended in the hot water of the boiler).