VEGETABLE PRODUCTS. 



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cinal property of certain vegetables, lias also 

 been ascertained to possess an alkaline quality. 

 This narcotic principle is obtained from the 

 milky and proper juices of some vegetables, and 

 from tlie infusion of the leaves or stem of others. 

 It exists in great quantity in the concrete juice 

 of the poppy, and is known ns opium. It is 

 soluble in boiling water and alcohol, as well as 

 in all acids. When distilled it emits white va- 

 poui-s, which are condensed into a yellow oil. 

 Some water and carbonate of ammonia pass into 

 the receiver, and at last carbonic acid gas, am- 

 monia, and carburetted hydrogen are disengaged, 

 and a bulky charcoal is left behind. Many other 

 substances besides opium possess narcotic quali- 

 ties. Thus the inspissated juice of the garden 

 lettuce resembles opium in its appearance and 

 qualities, and is obtained in a similar manner. 

 The deadly night shade furnishes a narcotic sub- 

 stance, as do also hemlock, black hellebore, 

 strammonium, and fox-glove. All these are active 

 poisons, if taken in largo quantity. 



Vegetable acids. The acids derived from the 

 vegetable kingdom have been multiplied by 

 modem chemists to the number of 116. Some 

 of these acids exist ready fomied in the juices 

 of the plant, as the acetic, oxalic, citric, malic, 

 &c.; otliers are in certain states of combination, 

 and do not exhibit their acid qualities until arti- 

 ficially decomposed, such as the camphoric, su- 

 beric, pyrolignous, &c. 



Oxalic acid. If the expressed juice of the 

 wood sorrel, (oxalis acetocella) is left to evaporate 

 slowly, it deposits small crystals of a yellowish 

 colour and saltish taste, which are known by 

 the name of salt of sorrel, that is, a salt with ex- 

 cess of acid ; from which the acid may be obtained 

 pure, by a simple chemical process. Oxalic acid, 

 In its pure state, is always solid. Its taste is 

 sharp and acrid. It is readily soluble in cold 

 water, and is distinguished from other acids by 

 its property of decomposing all calcareous salts, 

 and forming with lime a salt insoluble in water. 

 Hence it is used by chemists as a test to detect 

 tlie presence of calcareous salts. But it is not 

 used in medicine or the arts, except in its state 

 of acidulura, in which it is employed to make 

 a sort of lemonade, and to discharge stains of 

 ink. It has been found also in oxalis corniculata, 

 geranium aciduum,m the several species of rumex, 

 and in the pubescence of cicer arietinum. 



Acetic acid, or vinegar, which is generally man- 

 ufactured from wine or sugar in a certain stage 

 of fermentation, has also been found ready formed 

 in the sap of several trees, as analysed by Vau- 

 quelin; and also in the acid juice of the cicer 

 arietinum, of which it forms a constituent part. 

 It was obtained also by Scheele from the sap of 

 the sambrtcus nigra, and is consequently to be 

 regarded as a native vegetable acid. It is dis- 

 tinguished from other vegetable acids by its 



forming soluble salts with the alkalies and 

 earths. 



Citric acid. This substance exists in the 

 juice of the lemon. It has an agreeable acidu- 

 lous taste, especially when diluted with water. 

 By a red heat it yields carbonic acid gas, and 

 cai'buretted hydrogen gas, and is reduced to char- 

 coal. Nitric acid converts it into oxalic and 

 acetic acid; and with lime it forms a salt insol- 

 uble in water. It is much used as lemon juice 

 to give a seasoning to liquors, which it does 

 equally well in its concentrated state also. It 

 has been found in an unmixed state in the fol- 

 lowing vegetable substances : in the juice of 

 oranges and lemons, and in the berries of vaccin- 

 ium oxycoccits, vitis idaea, prunus padus, solanum 

 dulcamara, and rosa canina, as well as in many 

 fruits mixed with other acids. 



Malic acid. This acid is found in the juice 

 of unripe apples, whence it derives its name; but 

 it is found also in the juice of berberries, elder- 

 beiTies, gooseberries, plums and common house 

 leek. It cannot be obtained in a crystallized 

 and solid fonn; but if left exposed to the air, it 

 becomes thick and viscous. It is decomposed 

 by heat and strong acids; nitric acid converts it 

 into oxalic acid. It combines with the alkalies 

 and several of the metals, and forms with lime 

 a soluble salt, by which test it is distinguished 

 from other acids. It is used chiefly in the la- 

 boratory. 



Gallic acid. This acid is derived chiefly from 

 nut galls, by exposing a quantity of the powder 

 to a moderate heat in a glass retort, where the 

 acid will form on the top in octohedral crystals. 

 Its taste is austere and astringent; and it reddens 

 vegetable blues. It is soluble both in water and 

 alcohol, and communicates to solutions of iron 

 a deep purple or black colour. When exposed 

 to a gentle heat, it sublimes without alteration ; 

 but a strong heat decomposes it. Nitric acid 

 converts it into the malic and oxalic acids. It 

 is of great utility in the art of dyeing, and forms 

 the basis of all black colours, and of those with 

 a dark ground. It is an excellent test of the 

 presence of iron, and with the sulphate of iron 

 or copperas it forms common writing ink. 



Tartaric acid. In old wine which has been 

 kept in a caslc, a sediment is precipitated which 

 adheres to the sides and bottom, and forms a 

 crust known by the name of tartar, which is a 

 combination of potass and a peculiar acid in 

 excess. The compound is supertartrate of potass 

 and the acid in its state of purity is the tartaric 

 acid with potass; it forms a salt that is with 

 difficulty soluble. It exists in the following 

 vegetable substances : in the pulp of tamarinds, 

 in the juice of the grape, mulbenies, sorrel, and 

 sumac; and the roots of triticum repens, and 

 leontodon taraxacum. It is not much used except 

 by chemists; but the supertartrate, from which 



