The principles upon which the process at page 76 is based are all confirmed by further experience. These are that amylic alcohol freely dissolves all the alkaloids of cinchona barks, but does not dissolve the salts of those alkaloids, and that it dissolves much less of the coloring matter than other solvents; and the outline of the method is to break up the natural salts of the alkaloids in the bark, and fix the coloring matters by lime in excess. Then to extract the free alkaloids with amylic alcohol, ether being added to facilitate the percolation and filtration. Then to convert the alkaloids into salts, and thus get them out of the amylic alcohol into a watery solution. Then to precipitate them from the watery solution in the presence of chloroform, which dissolves them freely, and finally to evaporate off the chloroform and weigh the residue as anhydrous alkaloids.

Take of the powdered Cinchona 5 grammes=77.16 grains.

or, double all the quantities throughout, as well as size of vessels, etc., if the barks be poor, or if it be desired to divide the errors of manipulation.

Add to the lime contained in a 10 c.m.4 inch capsule, 30 c.c.= 1 fluidounce of hot water, and when the lime is slaked, stir the mixture, add the powdered cinchona, stir very thoroughly and digest in a warm place for a few hours, or over night. Then dry the mixture at a low temperature on a water bath, rub it to powder in the capsule and transfer it to a flask of 100 c.c.=3,3 fluidounces capacity, and add to it 25 c.c. fluidounce of amylic alcohol. Cork the flask and digest in a water bath at a boiling temperature and with frequent vigorous shaking for four hours. Then cool and add 60 c.c. 2 fluid ounces of stronger ether, s. g. 0.728, and again shake vigorously and frequently during an hour or more. Filter off the liquid through a double filter of 10 c.m.4 inches diameter into a flask of 150 c.c. 5 fluidounces capacity, and transfer the residue to the filter. Rinse out the flask onto the filter with a mixture of 10 volumes of amylic alcohol and 40 of stronger ether, and then percolate the residue on the filter with 15 c.c.-half a fluidounce of the

same mixture added drop by drop from a pipette to the edges of the filter and surface of the residue. Return the residue to the flask from whence it came, add 30 c.c.1 fluidounce of the amylic alcohol and ether mixture, shake vigorously for five minutes or more and return the whole to the filter. Again percolate the residue with 15 c.c. of the menstruum applied drop by drop from a pipette as before. Then put the filter and residue aside that it may be afterward tested in regard to the degree of exhaustion.

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Boil off the ether from the filtrate in the flask by means of a water bath, taking great care to avoid igniting the ether vapor, and also to avoid explosive boiling by having a long wire in the flask. When boiled down as far as practicable in the flask transfer the remainder to a tared capsule of 10 c. m. 4 inches diameter, and continue the evaporation on a water-bath until the contents are reduced to about 6 grammes=92 grains. Transfer this to a flask of 100 c. c. 3.3 fluidounces capacity, rinsing the capsule into the flask with not more than 4 c. c. 64 minims of amylic alcohol. Then add 6 c. c.96 minims of water and 4 c. c. 64 minims of normal solution of oxalic acid, and shake vigorously and frequently during half an hour. Pour the mixture while intimately mixed onto a well wetted double filter of 12 c. m. 4 inches diameter, and filter off the watery solution from the amylic alcohol into a tared capsule of 10 c. m.4 inches diameter. Wash the filter and contents with 5 c. c.= 80 minims of water applied drop by drop from a pipette to the edges of the filter and surface of the amylic alcohol. Then pour the amylic alcohol back into the flask over the edge of the filter and funnel, rinsing the last portion in with a few drops of water. Add 10 c. c. 160 minims of water and 1 c. c.16 minims of normal solution of oxalic acid; again shake vigorously for a minute or two, and return the whole to the wetted filter and filter off the watery portion into the capsule with the first portion. Return the amylic alcohol again to the flask, and repeat the washing with the same quantities of water and normal oxalic acid solution. When this has drained through, wash the filter and contents with 5 c. c.=80 minims of water applied drop by drop from a pipette. Evaporate the total filtrate in the capsule on a water-bath at a low temperature until it is reduced to about 15 grammes=241 grains, and transfer this to a flask of 100 c. c. 3.3 fluidounces capacity, rinsing the capsule into the flask with 5 c. c.80 minims of water. Add 20 c. c.='66 fluidounce of purified chloroform, and then 6.1 c. c.98 minims of normal solution of sodium, and shake vigorously for five minutes or

more. While still intimately mixed by the shaking, pour the mixture upon a filter of 12 c. m. 4 inches diameter well wetted with water. When the watery solution has passed through, leaving the chloroform on the filter, wash the filter and chloroform with 5 c. c.

80 minims of water applied drop by drop. Then transfer the chloroform solution by making a pin-hole in the point of the filter, to another filter of 10 c. m. 4 inches diameter, well wetted with 'chloroform, and placed over a tared flask of 100 c. c. 3.3 fluid ounces capacity. Wash the watery filter through into the chloroform-wet filter with 5 c. c. 80 minims of purified chloroform, and when this has passed through into the flask, wash the chloroform-wet filter also with 5 c. c.80 minims of chloroform, applied drop by drop to the edges of the filter. When the whole chloroform solution of alkaloids is collected in the flask, boil off the chloroform to dryness in a water bath, when the alkaloids will be left in warty groups of radiating crystals adhering over the bottom and sides of the flask. Place the flask on its side in a drying stove, and dry at 100° C.= 212° F. to a constant weight. The weight of the contents multiplied by 20 gives the percentage of the total alkaloids of the cinchona in an anhydrous condition, to within 1 or 2 of a per cent. if the process has been well managed.

The object of stirring the powdered bark into the slaked lime and water while hot is to swell and permeate the particles as rapidly as possible, introducing the lime solution into the innermost parts of the particles, and this process goes on during the digestion and drying of the mixture. Beside setting the alkaloids free from their natural combinations in the bark, the excess of lime so combines with and fixes the coloring matters, that even with the red cinchonas the subsequent steps of the process are not confused or obstructed by coloring matter.

Various other precipitants were tried with this and other menstrua, but none answered so well as lime. The menstruum of ether and alcohol with ammonia, recommended by Biel and adopted by Prollius and De Vrij, were tried, but did not do so well, as lime had to be subsequently used, while the creeping during evaporation was more difficult to avoid.

The digestion and shaking with amylic alcohol doubtless dissolves all the alkaloids present, and dissolves very little beside, but a portion of the solution remains absorbed by the spongy structure of the particles. Such portions can be percolated out on a filter with

amylic alcohol and without ether, but the filtration is very tedious and troublesome, requiring more than a day. But by diluting the amylic alcohol with about three times its volume of stronger ether it is rendered very manageable, and the filtration and washings are accomplished in about an hour, leaving the residue practically exhausted. If this solution be evaporated either spontaneously or by a water bath it creeps over the edges of the capsule badly, and no good result can be reached. But if it be boiled down in a flask in a water bath as directed, there is no difficulty, for after the ether is driven off the remainder has no tendency to creep over.

In this part of the process great care must be taken that the ether vapor does not take fire. When evaporated to 6 grammes as ascertained by trying on a scale from time to time, the ether is all gone and a solution of the alkaloids in amylic alcohol remains. One prominent object of the next step of the process, namely, the washing out of the alkaloids from the amylic alcohol as oxalates, is to free them from waxy and fatty matters always extracted from the bark by all solvents which effect a complete exhaustion. In washing out the alkaloids these waxy and fatty matters are left in solution in the amylic alcohol, and with it are thrown away.

If this amylic alcohol be evaporated on a water-bath to a constant weight, the residue will amount to about a half of one per cent. of the cinchona taken, and therefore if only a very rough estimate of the total alkaloids be needed, this may be obtained by continuing the evaporation of the amylic alcohol solution to a constant weight and subtracting a half of one per cent. from the result.

As the alkaloids are all soluble in amylic alcohol, while their salts are not, a definite quantity of solution of oxalic acid being added, the alkaloids are washed out of the amylic alcohol as acid oxalates. But they are rather difficult to wash out completely, and hence three washings are directed. If close results are not needed, two washings are sufficient. In pouring the amylic alcohol back from the filter into the flask, over the edge of the filter and funnel, a little dexterity is required, and the rim of the funnel must always be somewhat above the filter, in order to be quite successful. The double filter well wetted with water, and kept well wetted, retains the amylic alcohol very well, while the watery solution drains off to the last drop. But should there be any minute holes in the paper, or should the paper not be kept well wetted, a very little of the amylic alcohol may get through; but if so, it does not matter, for it will go off with the vapor in the subsequent evaporation, or

adhere to the capsule in an insoluble condition. The solution of the oxalates is too dilute for precipitation, and as it is not acid enough to injure the alkaloids by heat, it is evaporated to 15 grammes. As this solution has no tendency to creep, the evaporation is best done on a water-bath. In the next step the alkaloids are precipitated in the presence of chloroform, and it makes a very notable difference in the result if commercial or impure chloroform be used, hence purified chloroform is directed. Having used in all 6 c.c. of normal solution of oxalic acid in converting the alkaloids into acid oxalates, it is only necessary now to add 6.1 c.c. of normal solution of sodium in order to be sure that the precipitation is complete to an alkaline reaction, yet without a sufficient excess of sodium to hold the alkaloids from the chloroform; and hence the use of these normal solutions is important as well as very convenient. After a thorough shaking, the now free alkaloids are all dissolved in the chloroform, and it is only necessary to separate this completely in order to get them all. Here again a wet filter becomes a most complete and convenient mode of separation. The watery solution of oxalate of sodium goes through to the last drop, but not a particle of chloroform passes if the paper be good, and here a double filter is not needed; neither is it necessary to wash the filter very much. In the chloroform separation of the alkaloids a film of impurities, soluble in neither liquid, is apt to be present between the two liquids. This is often hardly a weighable quantity, and when small may be neglected and the chloroform solution be at once transferred to the tared flask for evaporation. But in close estimates it is easily separated in the way prescribed, by filtration of the chloroform solution through a chloroform-wetted filter into the flask. This chloroform-wetted filter not only excludes these impurities, but also any water that may drain out of the water-wetted filter. A pin-hole made in the point of the water-wetted filter is a very good way of transferring from one filter to the other.

The boiling down of the chloroform solution and drying the alkaloids to a constant weight and weighing them in a flask rather than in a capsule, is directed in order to have them in a condition convenient for estimating the ether-soluble alkaloids and quinia.

The above process gives a fairly good and trustworthy account of the total alkaloids in all the cinchona barks to which it has yet been applied, and is more conveniently and easily managed than any hitherto met with which is adapted to the moderate degree of skill possessed by this writer and by well-trained pharmacists generally.