The second method, adopted by Wood, in Sikkim, is much simpler: - The dry bark is crushed into small pieces - not powdered - and is put into casks, where it is macerated in the cold with very dilute hydrochloric acid; the liquor is then run off into wooden vessels, and mixed with an excess of strong solution caustic soda; the precipitate formed is collected on calico filters, and well washed with water. The precipitate is then gently dried, and powdered, constituting the crude febrifuge, which requires purifying. This is performed by dissolving the product in dilute sulphuric acid, and adding a small quantity of a solution of sulphur in caustic soda. After 24 hours, the liquor is carefully filtered; the filtrate is mixed with caustic soda, and the resulting precipitate is collected on calico, washed with a little water, dried, and powdered; it is then ready for use.
The operation is conducted in casks, worked in sets of three. Each cask receives 1 maund (82 lb.) of dry bark, which will undergo four successive macerations of half a week's duration, the liquor being passed through the three casks in rotation. The liquor used for the 4th (last) maceration is acidulated water; when drawn off, it forms the liquor for the 3rd cask; thence it is conducted to the 2nd cask; and finally to the 1st cask, containing new bark, whence it is run off for precipitation. When starting anew, each cask will contain dry bark, so that the system of rotation is not brought into full operation till after the first fortnight. The liquor for precipitation is run into tubs; the others are drawn into buckets, for transference to the respective casks. Acidulated water is made in a vat, by adding 1 gal. hydrochloric acid to 100 gal. water. The weight of acid used in the exhaustion is 6 1/2 per cent, of the weight of dry bark. The caustic soda solution consists of 1 part of the alkali dissolved in 3 parts of water; it is stored in iron vessels.
The quantity required for precipitation of the bark liquor is judged of by the curdy appearance assumed by the precipitate; every 100 lb. of dry bark consumes about 6 1/2 lb. of the alkali.
Filtration of the precipitate is commenced on the following day, when the liquor is transferred to the calico strainers, previously wetted. The first portions that run through are returned, until the passing liquor has a bright ruby colour; it is then allowed to flow away by a drain. When all the liquor has drained off, water is passed through the precipitate, until it ceases to acquire a red tint. The alkaloids on the filter should then exhibit a uniform cream-colour. The precipitate is dried, reduced to fine powder, and stored in suitable bins.
During the drying of the precipitate, a slight reddish-brown colour is developed; this is removed by the following process of purification: - 14 gal. of water are mixed with 2 pints of sulphuric acid, and 20 lb. of the dry powder; about 1/2 pint of solution of sulphur in caustic soda is stirred in, and the whole is left for 24 hours. It is then filtered through calico into a clean vessel, care being taken to get the liquor perfectly bright; about 6 gal. of water are used to wash the sediment left on the filters; the clear filtrate is thoroughly mixed with soda solution, to precipitate the alkaloids; the precipitate is collected on calico, washed with a small quantity of water, drained, dried, and reduced to fine powder. Wooden vessels are not so suitable for this operation as are those of enamelled iron, or earthenware.
The bark used is exclusively dry succi-rubrat and care is taken to mix the root-, stem-, and branch-barks together, as nearly as possible in the proportions in which they are yielded by the plantations. Green bark would not be available at all seasons; and it has been found that the trifling cost of drying the bark is more than repaid by the better product.
The purified febrifuge is a fine white powder, which, however, acquires a slight buff tint by keeping, it never agglutinates, and is freely soluble in weak acids, such as lemon-juice, etc. The cost price of this febrifuge is estimated at Is. 9d. an oz.; it is as efficient as quinine at 9s. an oz.
The bark is powdered, and boiled several times with sulphuric, or hydrochloric acid; after each boiling it is carefully expressed, and afterwards the liquors are mixed together. The quinine, cinchonine, and some impurities are precipitated with carbonate of soda, and the precipitate is collected in a cloth, compressed, dried, and digested with alcohol. The solution is next treated with dilute sulphuric acid, in sufficient quantity to exactly saturate the alkaloids, after which the alcohol is removed by boiling. The liquid is now allowed to cool, when the quinine is deposited as sulphate in crystals. The cinchonine, which is more soluble, remains in the mother-liquors. The crystals of sulphate of quinine are dissolved in alcohol, and the solution is decolorized by the addition of a little animal black; they are subsequently purified by re-crystallization. If the mother-liquors still contain quinine, they are precipitated by carbonate of soda, and the precipitate is re-dissolved in sulphuric acid. The sulphate of quinine is separated by repeated crystallizations.
Pure quinine may be prepared from the sulphate by precipitating it with a mineral alkali. (Spons' ' Encyclopaedia.')
Salicine is found in the bark and leaves of several species of Salts and Populus, but most abundantly in the white willow (S. alba) and aspen (P. iremuld). It is prepared as follows: -
(1) Exhaust willow bark by repeated coction with water, concentrate the mixed liquors, and, while boiling, add litharge until the liquid is nearly decolorized; filter, remove the dissolved oxide of lead, first by sulphuric acid, and afterwards by sulphuret of barium; filter, and evaporate, that crystals may form; the crystals must be purified by re-solution and re-crystallization. (Merck.)
(2) As No. 1, but using a stream of sulphuretted hydrogen to free the solution from lead.
(3) To a strong filtered decoction of willow bark add milk of lime, to throw down the colour; filter, evaporate the liquor to a syrupy consistence, add alcohol (sp. gr. .847), to separate the gummy matter, filter, distil off the spirit, evaporate the residue, and set it aside in a cool place to crystallize; the crystals are purified by solution in boiling water, agitation with a little animal charcoal, and re-crystallization.
Strychnine may be obtained from nux vomica (Strychnos nux vomica) and from the Ignatius bean (S. Ignatii) by the following methods: -
(1) Dissolve hydrochlorate or sulphate of strychnine in distilled water, and throw down the alkaloid with ammonia, carefully avoiding excess; re-dissolve the precipitate in hot rectified spirit, and collect the crystals .which form as the liquid cools.
(2) Nux vomica (in powder), 1 lb., is digested for 24 hours in 1/2 gal. of water acidulated with 2 fl. dr. of sulphuric acid, after which it is boiled for 1/2 hour, and the decoction decanted; the residue is boiled a second and a third time with a fresh 1/2 gal. of water acidulated with 1 fl. dr. of the acid, and the undissolved matter is finally submitted to strong expression; the decoctions are next filtered and concentrated to the consistence of a syrup, which is boiled with 3 pints rectified spirit for about 20 minutes, hydrate of calcium (1 6z., or q. s.) being added in successive portions during the ebullition, until the solution becomes distinctly alkaline; the liquid is then filtered, the spirit distilled off, and the residue dissolved in diluted sulphuric acid, q. s.; ammonia, in slight excess, is added to the filtered solution, and the precipitate which falls is collected upon a paper filter, and dried; it is next re-dissolved in a minimum of boiling rectified spirit, and digested with 1/2 oz. of animal charcoal for 20 minutes; the filtered liquid, as it cools, deposits strychnine in crystals.
(3) Nux vomica, 1 lb.; acetate of lead, 180 gr.; solution of ammonia, q. s. Subject the nux vomica for 2 hours to steam in any convenient vessel; chop or slice it; dry it in a water-bath or hot-air chamber, and immediately grind it in a coffee-mill. Digest the powder at a gentle heat for 12 hours with 2 pints of the spirit and 1 pint of the water, strain through linen, express strongly, and repeat the process twice. Distil off the spirit from the mixed fluid, evaporate -the watery residue to about 16 oz., and filter when cold. Add now the acetate of lead, previously dissolved in distilled water, so long as it contains any precipitate; filter; wash the precipitate with 10 oz. of cold water, adding the washings to the filtrate: evaporate the clear fluid to 8 oz., and, when it has cooled, add the ammonia in slight excess, stirring thoroughly. Let the mixture stand at the ordinary temperature for 12 hours: collect the precipitate on a filter, wash it once with a few oz. of cold distilled water, dry it in a water-bath or hot-air chamber, and boil it with successive portions of rectified spirit, till the fluid scarcely tastes bitter. Distil off most of the spirit, evaporate the residue to the bulk of about 1/2 oz., and set it aside to cool.
Cautiously pour off the yellowish mother-liquor (which contains the brucine of the seeds) from the white crust of strychnine which adheres to the vessel. Throw the crust on a paper filter, wash it with a mixture of 2 parts of rectified spirit and 1 of water, till the washings cease to become red on the 'addition of nitric acid; finally dissolve by boiling it with 1 oz. of rectified spirit, and set it aside to crystallize. More crystals may be obtained by evaporating the mother-liquor.
Veratrine is easily exhausted from the seeds of Veratrum Sabadilla, by the following process.
The crushed seeds are exhausted with a 2 to 3 per cent, solution of oxalic acid for 24 hours, when a clear liquid is afforded, and is neutralized by ammonia. After about 1/2 hour, a precipitate is formed in the liquid; this is separated by filtration and dissolved in pure cold alcohol. The alcoholic tincture, on evaporation, yields veratrine that is sufficiently white and crystalline. It is obtained perfectly so by dissolving in ether, without using any decolorizing material. (Alessandri.)