Cooley's Cyclopaedia of Practical Receipts Volume I Part 149

For the method of estimating the alkaloids in cinchona bark, see QUINOMETRY, QUININE, QUINIDINE, QUINOIDINE, QUINICONE, QUINAMINE, CINCHONINE; also the different pharmaceutical preparations of CINCHONA BARK.

=CINCHONIDINE.= _Syn._ CINCHONIDIA. C_{20}H_{24}N_{20}. This cinchona alkaloid is isomeric with cinchonine. It occurs in large, shining striated, rhombic prisms, which are anhydrous. It dissolves in 76 parts of ether and 20 of spirit of wine. The solutions are fluorescent, but do not answer to the chlorine and ammonia tests.

"The great powers and activity of this alkaloid have only of late been appreciated. As a protoplasm-poison, and probably in every other physiological action, it comes next to quinine and quinidine, and decidedly above cinchonine."[248]

[Footnote 248: Dr C. D. Phillips.]

If it is chemically pure, cinchonidine belongs to the non-fluorescent alkaloids.

=CINCHONINE.= _Syn._ CINCHONIA. C_{20}H_{24}N_{2}O. This alkaloid abounds most in the paler varieties of the cinchona barks. It occurs in clear, colourless, four-sided prisms, which are soluble in 30 parts of water, and in about 400 parts of ether and 120 of spirits of wine. With acids it forms soluble salts, which do not fluoresce in solution, and are turned lightish brown-yellow by the chlorine and ammonia tests. Of its salts, the hydriodate is readily soluble in water, and still more so in alcohol, whether dilute or strong. Cinchonine may be prepared from its sulphate or disulphate in the same way as quinine.

=Cinchonine, Sulphate of.= _Syn._ CINCHONIae SULPHAS. (Ph. U. S.) Take of the mother-water remaining after the crystallisation of sulphate of quinia in the process for preparing that salt a convenient quant.i.ty, solution of soda, alcohol, diluted sulphuric acid, animal charcoal in fine powder, each a sufficient quant.i.ty. To the mother-water add gradually with constant stirring solution of soda, until the liquid becomes alkaline.

Collect on a filter the precipitate formed, wash it with water, and dry it. Then wash it with successive small portions of alcohol to remove other alkaloids which may be present, mix the residue with 8 times its weight of water, and having heated the mixture, add gradually diluted sulphuric acid until it is neutralised and becomes clear. Then boil the liquid with animal charcoal, filter it while hot, and set it aside to crystallise.

Lastly, drain the crystals and dry them on bibulous paper. By evaporating the mother-liquid more crystals may be obtained.

=CINCHO-TANNIC ACID.= This acid is precipitated from a decoction of bark by acetate of lead, after the decoction has been freed from cinchona red by means of magnesia.

If the cincho-tannate of lead thus formed be decomposed by sulphuretted hydrogen, and the solution carefully evaporated in vacuo, the acid may be obtained as an amorphous, hygroscopic substance, readily soluble in water.

A ferric salt added to a solution of this acid imparts a greenish colour to it.

Cincho-tannic acid is very soluble in water, but not in acids. Therefore a concentrated watery infusion (1 to 4) of Indian bark gives a precipitate upon the addition of strong hydrochloric acid. By this means a rough estimation may be formed of the amount of cincho-tannic acid in a sample of bark.

=CINCHOVATINE.= The substance known under this name does not exist as an alkaloid, _sui generis_. It is nothing more than quinidine, or cinchonidine, or a mixture of both.

=CINNABAR.= _Syn._ NATIVE VERMILLION. This compound, which is one of the most abundant of the ores of mercury, is a product of considerable importance in the arts, and some portions of it are sometimes sufficiently pure in colour to be used after mere levigation. Generally, however, the fact.i.tious kind is employed. See VERMILION.

=CINNAMEIN.= C_{16}H_{14}O_{2}. _Syn._ OIL OF BALSAM OF PERU. A volatile oil existing in balsam of Peru.

=CINNAMIC ACID.= HC_{9}H_{7}O_{2}. A colourless, transparent, crystalline substance, obtained from oil of cinnamon, liquid storax, balsam of Peru, and balsam of tolu. It is freely dissolved by alcohol, but nearly insoluble in water. At 248 Fahr. it fuses, and at 560 Fahr. it sublimes unchanged. Distilled with dichromate of pota.s.sium and sulphuric acid it is converted into benzoic acid. Its salts are called cinnamates.

=CINNAMON.= _Syn._ CINNAMON BARK; CINNAMOMI CORTEX (B. P.), L. The inner bark of shoots from the truncated stock of the _Cinnamomum Zeylanic.u.m_, imported from Ceylon, and distinguished in commerce as Ceylon cinnamon.

The best is obtained from branches about three years old.

Used in _medicine_ as a carminative and astringent, chiefly as an adjuvant to other medicines, _e.g._ with chalk, in diarrha.--_Dose_, 10 to 20 grains.

_Obs._ Owing to the high price of this drug it has become a general practice to subst.i.tute the bark of ca.s.sia (_Ca.s.sia_; _Cortex cinnamomi ca.s.sia_) for it, which so closely resembles it in flavour that the uninitiated regard them as the same. Ca.s.sia, however, is not only thicker and coa.r.s.er than cinnamon, but its fracture is short and resinous, and its flavour is more biting and hot, whilst it lacks the peculiar sweetish taste of cinnamon. The thickness of cinnamon seldom exceeds that of good drawing paper.

=CISTERNS.= See TANKS.

=CITRATE.= A salt in which the hydrogen of citric acid is replaced by a metal or other basic radical.

=CIT'RIC ACID.= H_{3}C_{6}H_{5}O_{7},H_{2}O. _Syn._ ACID OF LEMONS, CONCRETE A. OF L.; AC'IDUM LIMO'NIS, ACIDUM CIT'RIc.u.m (B. P.), L.; ACIDE CITRIQUE, Fr.; CITRONENSAuRE, Ger. An acid peculiar to the vegetable kingdom. It is obtained in large quant.i.ty from the juice of lemons and other fruits of the genus CITRUS; it is also found in gooseberries, currants, cranberries, whortleberries, cherries, &c.; and Dr Wright has lately found it in great abundance in unripe mulberries, in conjunction with malic acid.

When currants or gooseberries are employed as a source of citric acid, they are first subjected to pressure, and the juice so obtained from them is then fermented. The fermented liquor is next submitted to distillation, and the alcohol collected.

The residue in the retort containing the citric acid is saturated with chalk, and the resulting citrate of lime is decomposed by means of sulphuric acid.

100 lbs. of the fruit are said to yield 10 lbs. of spirit and 1 lb. of acid.

_Prep._ The citric acid manufacture consists in separating it from the mucilage, sugar, and other foreign matter with which it is combined in the juice of lemons and limes.

1. (Ph. L. 1836,--Scheele's process.) Take of lemon juice 4 pints; prepared chalk, 4-1/2 oz.; diluted sulphuric acid, 27-1/2 fl. oz.; distilled water, 2 pints. Add the chalk by degrees to the lemon juice, made hot, and mix well; set by, that the powder may subside, and afterwards pour off the supernatant liquor. Wash the precipitated citrate of lime frequently with warm water; then pour upon it the diluted sulphuric acid, mixed with the distilled water, and boil the whole for 15 minutes in gla.s.s, stoneware, or lead; press the mixture strongly through a linen cloth, and filter it. Evaporate the filtered liquor with a gentle heat, and set it aside, that crystals may form. To obtain the crystals pure, dissolve them in water a second and a third time; filter each solution, evaporate, and set it apart to crystallise.

2. (Ph. L. 1851.) Merely placed in the materia medica.

3. (Ph. E. 1841.) Similar to that of Ph. L. 1836, except that the washed citrate of lime is ordered to be squeezed in a powerful press, and that the filtered solution of citric acid is ordered to be tested with nitrate of baryta, and if the precipitate is not nearly all soluble in nitric acid, to add a little citrate of lime to the whole liquor, till it stands this test.

4. (Ph. D. 1826.) Same as that of Ph. L. 1836.

5. (Ph. D. 1851.) Included in the materia medica.

6. (P. B. 1867.) Differs from the process of the Ph. L. 1836 in some unimportant detail only.

7. (Dr Price.) The crude juice is saturated with ammonia, pota.s.sa, or soda (carbonates), or with the ammoniacal product distilled from gas-liquor; chalk, 150 parts, or hydrate of lime, 90 parts, are then added for every 192 parts of citric acid contained in the liquor, and the whole stirred well together; heat is next applied, and the ammonia distilled into another quant.i.ty of lemon juice; the citrate of lime thus obtained is then decomposed with dilute sulphuric acid, and the whole process conducted as before. When pota.s.sa or soda is used the distillation is omitted, and the expressed liquor, after filtration, used to decompose fresh lemon juice.

8. (Ordinary manufacturing process.) To crude lemon or lime juice, mixed with water, is added ground chalk; the precipitate is washed to free it from the impurities dissolved in the water, and afterwards decomposed by sulphuric acid. If the citric acid is not sufficiently white, it is decolorised by digestion with animal black.

9. (Kuhlman.) This chemist proposes saturating the hot lemon juice as far as possible with very finely divided barium carbonate, and afterwards completing the neutralisation with barium hydrate or sulphide. The precipitated barium citrate is then to be washed, and decomposed with the requisite quant.i.ty of sulphuric acid. The advantage of barium over lime as a precipitant is the more ready crystallisability of the citric acid from the solution thus obtained. Sulphate of baryta is absolutely insoluble in solution of citric acid, whilst sulphate of lime is not; and the presence of the latter impedes the crystallisation of the acid.

_Obs._ If the lemon or lime juice be allowed to ferment a short time, the mucilage and other impurities will, to a certain extent, separate and subside. See _Concluding Remarks_.

_Prop., Uses, &c._ Citric acid forms rhomboidal prisms, which are clear, colourless, odourless, sour, and deliquescent in a moist atmosphere. It is an agreeable acid, at once cooling and antiseptic. It is much used in medicine as a subst.i.tute for lemon juice, and to form effervescing draughts, citrates, &c.

17 gr. citric acid, in crystals, or 1/2 fl. oz. of lemon juice,

---------------------v--------------------------/ are equivalent to /----------^--------------- 25 gr. bicarbonate of potash; 20 " carbonate of potash; 15 " carbonate of ammonia; 20 " bicarbonate of soda; 35 " carbonate of soda.

The bicarbonate of pota.s.sa is that generally preferred for making saline draughts with citric acid; and when flavoured with a little tincture of orange peel and simple syrup, or syrup of orange peel alone, it forms a most delicious effervescing beverage. Citric acid in pure crystals or in lime juice is much used by the calico-printer, being the best known 'resistant' for iron and alumina mordants.

_Pur._ Citric acid is frequently met with adulterated with tartaric acid; the fraud is easily detected by dissolving the acid in a little cold water, and adding to the solution a small quant.i.ty of acetate of potash.

If tartaric acid be present, a white, crystalline precipitate of cream of tartar will be produced on agitation. When pure it is devoid of colour, is entirely, or almost entirely, decomposed by heat. It is soluble in water and in spirit, and what is thrown down from its watery solution by acetate of lead is dissolved by nitric acid. No salt of pota.s.sium precipitates anything with citric acid except the tartrate. When a few drops of a solution of citric acid are added to lime water, a clear liquid results, which, when heated, deposits a white powder, soluble in acids without effervescence. By the action of nitric acid citric acid is converted into oxalic acid.

When the crystals of citric acid are very deliquescent, the presence of free sulphuric acid may be suspected. This latter may be detected with facility by dissolving the citric acid in a little water, strongly acidifying the solution with hydrochloric acid, and adding chloride of barium, when, if sulphuric acid be present, an insoluble precipitate of sulphate of barium will fall down after a short time. Oxalic acid is sometimes present in citric acid, the cause of its presence being explained further on. To test for it proceed as follows:

Dissolve a small quant.i.ty of the citric acid in water, and add to the solution an excess of ammonia; acidify with acetic acid, filter, and test the filtrate with calcium sulphate.

_Estim._ See ACIDIMETRY and LIME JUICE.

_Tests._ See _above_.

_Concluding Remarks._ The preparation of citric acid has now become an important branch of chemical manufacture, from the large consumption of this article in various operations in the arts. In conducting the different steps of the process some little expertness and care are, however, necessary to ensure success. The chalk employed, which should be dry, and in fine powder, is added to the juice from a weighed sample, until the latter is perfectly neutralised, and the quant.i.ty consumed is exactly noted. The precipitated citrate of lime is next thoroughly washed with water, and the sulphuric acid, diluted with 6 or 8 times its weight of water, whilst still warm, is poured upon it, and thoroughly mixed with it. The agitation is occasionally renewed for 8 or 10 hours or longer, when the solution of citric acid is poured off, and the residuum of sulphate of lime thoroughly washed with warm water, the washings being added to the liquid acid. This last is then poured off from the impurities that may have been deposited, and evaporated in a leaden boiler, over the naked fire, or by high-pressure steam, until it acquires the gravity of 113, when the process is continued, at a lower temperature, until a syrupy aspect is a.s.sumed, and a pellicle appears on the surface of the liquor. Without great care at this part of the process the whole batch may be carbonised and spoiled. At this point the concentrated solution is emptied into warm and clean crystallising vessels, set in a dry apartment, where the thermometer does not fall below temperate. At the end of 4 days the crystals are found ready for removal from the pans. They are thoroughly drained, redissolved in as little water as possible, and after being allowed to stand for a few hours to deposit impurities, again evaporated and crystallised.

The acid of the second crystallisation is usually sufficiently pure for the market; when this is not the case a third, or even a fourth, crystallisation must be had recourse to. The mother-liquors from the several pans are now collected together, and a second or third crop of crystals obtained from them, by evaporation as before.

A frequent cause of difficulty in obtaining crystals from the solutions is the employment of too little sulphuric acid to decompose the whole of the citrate of lime; the consequence of which is that a little of that salt is taken up by the free citric acid, and materially obstructs the crystallisation. Forty parts of dry sulphuric acid are required to decompose 50 parts of chalk. Commercial sulphuric acid (oil of vitriol) is usually of the sp. gr. of 1845, and it therefore requires 49 lbs. of this acid for every 50 lbs. of chalk employed in the process. In practice it is found that a very slight excess of sulphuric acid is preferable to a preponderance of undecomposed citrate of lime.

The first crop of crystals is called 'brown citric acid,' and is chiefly sold to the calico-printers. Sometimes a little nitric acid is added to the solution of the coloured crystals, for the purpose of bleaching them, but in this way a minute quant.i.ty of oxalic acid is formed. A more general plan is to bleach the citrate of lime by covering it with a weak solution of chloride of lime, exposing it in shallow vessels to the sun's rays, and rewashing it before decomposing it with sulphuric acid. A safer plan is to dissolve the crude citric acid, digest with animal charcoal, and again concentrate the solution to the crystallising point.