VIII.-DISTILLATION WITH Water.

In the preceding analytical course the volatile oils have found no place, though their presence might have been conspicuous sometimes, especially in the ethereous extract. For their production and examination another sample of the substance must be employed, but not less than 1 kilogram, or much more account of the comparatively small amount of volatile oil contained in most plants.

on

Besides volatile oils there are other ingredients of plants that have been obtained in the preceding analysis in too small a quantity or not at all, and the discovery of which becomes easier with a larger amount of raw material.

The production of these two classes of bodies may be combined in the following way :

(a) Macerate the substance with water for one or two days and distil, preferably on the water-bath and by means of steam, in a Beindorf's apparatus, described on p. 277, and provided with a good refrigerator. From what will be seen afterwards the weight of the empty tin still (without head or other accessories) must be determined and engraved on the tin. As recipient, a Florentine flask or a similar contrivance is employed.

The distilling water dissolves invariably certain quantities of oil. Either more oil is present than requisite for saturating the water, or there is less of it. In the first case the oil separates on or under the water, according to its density. To clarify the at first usually turbid oil allow to stand undisturbed for a few days, and prevent the solidifying of some oils by keeping them in a moderately warm place. After it has become clear, and if it floats on the water, remove it by means of a thin cotton wick, used as a syphon; if it be heavier than water, pour off the latter and remove the rest by means of the same syphon.

If no volatile oil has been separated in the distillate, i.e., if the water has not been saturated with it, a saturation or separation may be obtained in most cases by submitting the distillate to another distillation with a fresh quantity of raw material so as to increase the amount of oil in the same quantity of water. Sometimes this process (cohobation) must be repeated a third time. Should it be desirable to obtain the oil without distilling two or three times, the aqueous distillate must be shaken with one-fifth its volume of ether for half-an-hour. Allow the mixture to become clear, pour off the ether and let evaporate spontaneously in a beaker. The volatile oil, mixed with a few drops of water, remains, though only in very small quantity.

In order to enable an investigation of more than the external characters of a volatile oil (colour, smell, taste, density) at least 50

Y

grams of it are required. The examination has to be conducted as indicated under Essential Oils, p. 77.

(b) 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 latter removes both oil and acid.

Test first on hydrocyanic acid, and employ in case of its presence a weighed quantity of the distillate for its quantitative estimation. Both is done according to the instruction given under "Hydrocyanic acid," p. 107.

Now mix the rest of the distillate with carbonate of baryta, rubbed down so as to form a fine milk, and evaporate on the water-bath, driving away together with the water any hydrocyanic 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 examined 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 conducting the steam, the head and the false bottom of the still, place the latter on the balance and determine the weight of the water 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 the 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 continue 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 stirring 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 off 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 purpose the still is left suspended in the hot water of the boiler).

The contents of the still are now either a clear liquid or―more frequently a fat is floating on the surface and a resin has subsided. Pour off from the latter and remove the fat by filtering through a wet filter.

All these three substances-resin, fat, aqueous liquid-together with the remaining substance, have to be examined separately.

(a) The resinous mass is usually of a dark colour. Wash with water and try if it contains an alkaloid by triturating it assiduously with water containing 1-20th of its weight hydrochloric acid of 1.12 specific gravity, keeping at ordinary temperature for a few hours (heat applied with the acid is liable to split up the resin), filter the acid watery solution and wash the resin well with water.

a. Evaporate the acid liquid at a very gentle heat, try any crystalline or non-crystalline residue with the proper tests (II., B, a) and see, if it be a new or a known alkaloïd.

B. The resinous mass, remaining in a, is compared with the resin obtained previously (II., A and III., B), and the knowledge of the latter is, if necessary, completed by means of the resin now obtained.

(b) Submit the fat to the same treatment with hydrochloric acid and water as the resin, examine the acid liquid for alkaloïds, compare the fat with the fat obtained previously (II., A, B), and complete its investigation by means of the new material.

(c) Over-saturate a small sample of the aqueous solution of invariably acid reaction with ammonia. If a precipitate is obtained hereby, precipitate the whole liquid with ammonia. If no precipitate has been obtained with ammonia, try in the same way successively carbonate of ammonia, ley of potash (or of soda) and carbonates and bicarbonates of potash or of soda.

α.

Let the precipitate, obtained by means of the above tests, subside, wash, dry, triturate, digest with alcohol of 90°, warm, filter, evaporate the alcohol and examine any remnant on alkaloïds (II., B, a).

B. Precipitate the liquid remaining in c, after it has been made slightly acid with acetic acid, or the original clear liquid, in case no precipitate has been produced by alkalies, with acetate of lead completely and proceed according to II., B, e. The chief object is in this case the investigation of non-volatile organic acids and the completion of the former investigations.

(d) The remaining mass, exhausted by alcohol of 45%, contains most of the gum, and may be used for determining this substance if the former investigations (IV.) have been without a satisfactory result. For this purpose spread it on shallow dishes to drive off the alcohol, mix with cold water, strain after some time, press, let the liquid subside, decant, evaporate to a small bulk, and throw down the gum by means of alcohol, &c., according to the instructions given under "Gum," p. 99.

IX.-DISTILLATION WITH ACID WATER.

In distilling vegetable substances with water, volatile acids are obtained in the distillate, but generally in such small quantities (except hydrocyanic acid) that it is often impossible, especially in a mixture, to recognise their nature. In order to obtain larger quantities of these volatile acids, the distillation with acid water is resorted to, while employing at least 1 kilogram of fresh raw material, or larger quantities if required.

Usually sulphuric acid is used for this purpose, although phosphoric acid is preferable on account of its non-volatility, and because it does not become decomposed towards the end of the distillation, while sulphuric acid is reduced to sulphurous acid, which passes over and adulterates the distillate. The volatile anorganic acids occurring in plants (hydrochloric and nitric acids) are likewise obtained by distilling with sulphuric or phosphoric acid, but the hydrochloric acid may easily be removed from the distillate, and the presence of nitric acid is of less consequence.

As the volatile acids (i.e., those volatile by the steam of water, consequently not benzoic, cinnamic, oxalic, &c., acids) are always contained in plants as compounds soluble in water, the distillation of the aqueous extract is preferable to the distillation of the whole vegetable substance. Prepare, therefore, first an aqueous extract by mixing the finely-comminuted substance with four to six times its weight of pure water; keeping the whole for one day at a gentle heat (in the tin still of Beindorf's apparatus); straining, pressing, adding 50 to 60 grams phosphoric acid to every kilogram of the liquid; filtering (filtering before the addition of the acid would have been difficult or impossible; should it prove difficult still, subsiding instead of filtering must be resorted to) and adding a solution of sulphate of silver, as long as a precipitate is produced. Allow the chloride of silver to subside, filter, pour the filtrate into a glass retort, and distil twothirds by means of a good refrigerator.

Pour the distillate into a porcelain-dish, add an adequate quantity (for every kilogram of raw material, about 10 grams) of carbonate of baryta, rubbed down to the finest powder with a portion of the distillate, and evaporate under assiduous stirring with a glass-rod on the water-bath. Any hydrocyanic acid present in the distillate evaporates, while the other volatile organic acids combine with the baryta, and remain in the liquid. Should the whole of the carbonate of baryta be dissolved in evaporating, a fresh portion of it must be added in order to prevent the loss of volatile acids. After the liquid has reached a certain concentration, and is no longer of acid reaction, it is filtered, and the contents of the filter are edulcorated with water.

The examination of the contents of the filter, and of the filtrate, is conducted according to II., A, b; but, besides the low acids of the fat-acid series named there, other acids, as angelic, salicylous, &c., acids, must not be neglected, or even the investigation of as yet unknown acids.

The discovery and estimation of (with water) non-volatile acids is not effected with the liquid remaining from the distillation of the volatile acids, on account of the great amount of phosphoric acid contained in it; but, with the liquid c, ẞ of the preceding (VIII.) section; whereas the acid remnant, if necessary, may be employed for the investigation of volatile alkaloïds (X.)

X.-DISTILLATION WITH ALKALINE WATER.

For a thorough investigation of volatile alkaloïds, at least 1 kilogram of the dried raw material is required. Similar to volatile acids, their separation is effected best by distilling the aqueous extract of the respective vegetable substance with an alkali, for the reason given before, and in order to prevent rising of the liquid and evolution of much ammonia. The latter is obtained, indeed, even in distilling the extract, because no vegetable extract is free from ammonia-salts or from other nitrogenised compounds, but in much less quantity.

Extract the substance by a warm digestion with four to six times its quantity of water (which, in presence of tannic acid, is mixed with 1-25th its weight hydrochloric acid of 1·12 specific gravity), press, pour the whole liquid into a copper-boiler (well adapted for this purpose is the boiler of the Beindorf's apparatus); saturate with slaked lime, add as much lime, slaked and mixed with water to the finest pulp, as to effect an excess of 50 grams quick-lime to every kilogram of raw material, and distil by means of a good refrigerator, until the distilling water is void or nearly void of alkaline reaction.

In case of any scarcity of raw material, the investigation of volatile alkaloïds may be effected by means of the acid residue left from the distillation under IX., but modified in such a way as to use caustic soda instead of quicklime, in order to prevent the formation of insoluble phosphate of lime.

Saturate the whole distillate exactly with diluted sulphuric acid, evaporate on the water-bath, and after due concentration in a weighed dish under the receiver of an air-pump, until no further loss of weight be observed. Weigh the salty remnant, triturate if necessary, shake in a flask with absolute alcohol; collect the insoluble portion (sulphate of ammonia) on a filter, wash with absolute alcohol, dry by means of the air-pump, and weigh. By subtracting the latter weight from that of the whole remnant, the quantity of the sulphate of the alkaloïd is obtained; and by deter