Book I. 



C0MF0UNJ3 PRODliCTS OF PLANTS. 



149 



646. According to Parmentier, starch may be extracted from a number of plants ; as arctium lappa, 

 atropa belladonna, polygonum bistortj, bryoniaalba, colchicum autumnale, spiraea filipendula, ranunculus 

 bulbosus, scrophularia nodosa, sambucus ebulus and nigra, orchis morio and mascula, imperatoria ostru- 

 tliium, hyoscyamus niger, rumex obtusifolius, acutus, and aquaticus, arum maculatum, iris pseudacorus 

 and fcetidissima, orobus tuberosus, bunium bulbocastanum. It is found also in the following seeds : 

 wheat, barley, oats, rice, maize, millet-seed, chestnut, horse-chestnut, peas, beans, acorns. 



647. Starch is an extremely nutritive substance, and forms one of the principal ingredients in almost all 

 articles of vegetable food used, whether by man or the inferior animals. The latter feed upon it in the 

 state in which nature presents it ; but man prepares and purines it so as to render it pleasing to his taste, 

 and uses it under the various modifications of bread, pastry, or confectionary. Its utility is also consider- 

 able in medicine and in the arts ; in the preparation of anodyne and strengthening medicaments, and in 

 the composition of cements ; in the clearmg and stiHening of linen ; and in the manufacture of hair- 

 powder. 



' ■ 648. Gluten is that part of the paste formed from the flour of wheat that remains unaffected by the 

 water after all the starch contained in it has been washed off". It is a tough and elastic substance, of a 

 dull white color, without taste, but of a very peculiar smeli. It is soluble in the acids and alkalies, but 

 insoluble in water and in alcohol. Glut'jn has been detected, under one modification or other, in a very 

 considerable number of vegetables or vegetable substances, as well as in the flour of wheat. Kouelle, the 

 younger, showed that it exists in the green fecula of plants ; and i'roust found it in the following grains 

 and fruits ; peas, beans, barley, rye, acorns, chestnuts, horse-chestnuts, apples, quinces, alder-berries, 

 grapes. He found it also in the leaves of rue, cabbage, cresses, hemlock, borage, and saflron, and in the 

 petals of the rose. 



649. Gluten is one of the most important of all vegetable substances, as being the principle that renders 

 the flour of wheat so fit for forming bread, by its occasioning the panary fermentation, and making the 

 bread light and porous. It is used also as a cement, and capable of being used as a varnish, and a ground 

 for paint. 



650. Albumen, which is a thick, glary, and tasteless fluid, resembling the white of an unboiled egg, is a 

 substance that has been but lately proved to exist in the vegetable kingdom. Its existence was first an- 

 nounced by Fourcroy, and finally demonstrated by the experiments of Vauquelin on the dried juice of the 

 papaw-tree. It is nearly related to animal gluten, and the elements of its composition are, carbon 52-883 ; 

 oxygen 23'872; hydrogen 7'540 ; nitrogen 15.705; total 100. Albumen has not been found in such 

 abundance in any other plant, as in the plant above specified. But it has been found to exist in mush- 

 rooms, and some other of the fungi. And the juice of the fruit of hibiscus esculentus, a West Indian plant, 

 is said to contain such a proportion of it as to render it fit to be employed as a substitute for the vv^hite of 

 eggs, in clarifying the juice of the sugar-cane. Almonds also, and other kernels from which emulsions are 

 made, have been found to contain a substance possessing the properties of curd, which resembles albumen 

 very ctosely. 



651. Fibrina is a peculiar substance which chemists extract from the blood and muscles of animrJs. This 

 substance constitutes the fibrous part of the muscles, and resembles gluten in its appearance and elasticity. 

 A substance possessing the same properties has been detected by Vauquelin in the juice of the papaw-tree, 

 which is called vegetable fibrina. 



652. Extract. When vegetable substances are macerated in water, a considerable portion of them is 

 dissolved ; and if the water is again evaporated, the substance held in solution may be obtained in a sepa- 

 rate state. This substance is denominated extract. But it is evident that extract thus obtained will not 

 be precisely the same principle in every different plant, but will vary in its character according to the 

 species producing it, or the soil in which the plant has grov/n, or some other accidental cause. Its dis- 

 tinguishing properties are the following : it is soluble in water as it is obtained from the vegetable, but 

 becomes afterwards insoluble in consequence of the absorption of oxygen from the atmosphere. It is solu- 

 ble in alcohol ; and it unites with alkalies, and forms compounds which are soluble in water. When 

 distilled it yields an acid fluid impregnated with ammonia, atid seems to be composed principally of hydro- 

 gen, oxygen, carbon, and a little nitrogen. Extract, or tlie extractive principle, is found in a greater 

 or less proportion in almost all plants whatever, and is very generally an ingredient of the sap and bark, 

 particularly in barks of an astringent taste. But still it is not exactly the same in all individual plants, 

 even when separated as much as possible from extraneous substances. It nv^y, therefore, be regarded as 

 constituting several different species, of which the following are the most remarkable : — 



Extract of catechu. This extract is obtained from an infu- 

 sion of the wood or powder of catechu in cold water. Its 

 color is a pale brown ; and its taste slightly astringent. It is 

 precipitated from its solution by nitrate of lead, and yields 

 Dy distillation carbonic and carburetted hydrogene gas, leaving 

 a porous charcoal. 



Extract of senna. This extract is obtained from an infu- 

 sion of the dried leaves of cassia senna in alcohol. The color 

 of the infusion is brownish, the taste slightly bitter, and the 

 smell aromatic. It is precipitated from its solution by the 

 muriatic and oxymuriatic acids ; and when thrown on burning 

 coals consumes, with a thick smoke and aromatic odor, leavijig 

 behind a spongy charcoal. 



Extract of qtiinqtiina. This extract was obtained by Four- 

 croy, by evaporating a decoction of the bark of the quinquina 

 of St. Domingo in water, and again dissolving it in ali'ohol, 

 which finally deposited by evaporation the peculiar extractive. 

 It is insoluble in cold water, but very soluble in boiling water ; 

 its color is brown, and its taste bitter. It is precipitated from 

 its solution by lime-v/ater, in the form of a red powder; and 

 when dry it is black and brittle, breaking with a polished 

 fracture. 



Extract of saffron. This extract is obtained in great aljun- 

 dance from tlie summits of the pistils of crocus sativus, wliich 

 are almost wholly soluble m water. 



653. Extracts were formerly much employed in medicine; though their elFicacy seems to have been 

 overrated. But a circumstance of much more importance to society is that of their utility in the art of 

 dyeing. By far the greater part of colors used in dyeing are obtained from vegetiible extracts, whicl) 

 have a strong affinity to the fibres of cotton or linen, with which they enter into a combhiation that is 

 rendered still stronger by the intervention of mordants. 



654. Coloring matter. The beauty and variety of the coloring of vegetables, chemists have ascribed to 

 the modifications of a peculiar substance which they denominate the coloring principle, and which they 

 have accordingly endeavored to isolate and extract ; first, by means of m:iccration or boiling in water, 

 and then by precipitating it from its solution. The chemical properties of coloring matter seem to be as 

 yet but imperfectly known, though they have been considerably elucidated by the investigations of Ber- 

 tholet, Chaptal, and others. Its aflSnities to oxygen, alkalies, earths, motaUic oxides, and cloths fabri- 

 cated, whether of animal or vegetable substances, such as wool or flax, seem to be among its most striking 

 characteristics. But its affinity to animal substances is stronger than Its afinnity to vegetable substances ; 

 and hence wool and silk assume a deeper die, and retain it longer than cotton or linen. Coloring matter 

 exhibits a great variety of difierent tints, as it occurs in different species of plants ; and as it combines 

 with oxygen, which it absorbs from the atmosphere, it assumes a deeper shade ; but it loses at the same 

 time a portion of its hydrogen, and becomes insoluble in water ; and thus it indicates its relation to ex- 

 tract. Fourcroy reduced colors to the four following sorts ; extractive colors, oxygenated colors, carbo- 

 nated colors, and hydrogenated colors ; the first being soluble in water, and requiring the aid of saline or 

 vnotallic mordants to fix them upon cloth ; the second being insoluble in water, as altered by the absorp- 

 tion of oxygen, and requiring no mordant to fix them upon cloth ; the third containing in their compo- 

 sition a great proportion of carbon, but soIudIc in alkalies; and the fourth containing a great proportion 

 of resin, but soluble in oils and alcohol. But the simplest mode of arrangement is that by which the dif- 

 ferent species of coloring matter are cLxssfd according to their effect in the art of dyeing. The prinrij'al 

 and fundamental colors in this art arc the blue, the red, the yellow, and the brown. 



I. 3 



