VKaETABLE PRODUCTS. 



Ul 



months, when its leaves are gathered, and im- 

 mersed in vessels filled with water till femienta- 

 tion takes place. The water then becomes opaque 

 and green, exhaling an odour like that of vola- 

 tile alkali, and evolving hubbies of carbonic acid 

 gas. When the fermentation has been continued 

 long enough, the liquor is decanted and put into 

 other vessels, where it is agitated till blue flakes 

 begin to appear. Water is now poured in, and 

 the flakes are precipitated in the form of a blue 

 powdery sediment, which is obtained by decan- 

 tation; and which, after being made up into 

 small lumps, and dried in the shade, forms the 

 indigo of commerce. It is insoluble in water, 

 though slightly soluble in alcohol ; but its true 

 solvent is sulphuric acid, with which it forms a 

 fine blue dye, knovm as liquid blue. Several 

 other plants also yield indigo, and particularly 

 the isatis tinctoria, or woad, a plant indigenous 

 to Britain, and thought to be the plant with the 

 juice of which the ancient Britons stained their 

 naked bodies, to make them look terrible to their 

 enemies. If this plant is digested in alcohol, and 

 the solution evaporated, white crystalline grains, 

 somewhat resembling starch, will be left behind, 

 which grains are indigo, and they will become 

 gradually blue by the action of the atmosphere. 

 The blue colour of indigo, therefore, is owing to 

 its combination with oxygen. Litmus, or tum- 

 Bole, is procured from a species of lichen, hcinora 

 tartarea, found chiefly in Norway. These lich- 

 fns are cleaned and powdered, and mixed with 

 putrid urine. The ammonia of the urine acts on 

 the powder, and a fermentation is produced, and 

 a blue colour is developed. Acids, even of the 

 weakest kind, redden this blue very readily ; and 

 hence paper stained with litmus is a frequent test 

 of the presence of acids. 



A red colour is produced from the root, stem, 

 or flower, of the five following plants : 1st. From 

 the roots and stems of rubia tinctorum, or mad- 

 der, dried, bruised, and sifted, a powder is ob- 

 tained, that is soluble in alcohol, and partly sol- 

 uble in water, find dyes cloth, by means of pro- 

 per mordaunts, either violet or red. The red 

 colour is very beautiful. This powder not only 

 tinges vegetable matters, but will communicate 

 a red hue to the bones of animals, if mixed with 

 their food. 2d. From two species of lichens 

 (lichen roccella aniparellasj, when dried, pow- 

 dered, macerated in water, and mixed with a 

 solution of muriate of tin, a fine red dye is ob- 

 tained, which, however, is very evanescent on 

 ordinary articles, though more permanent on 

 marble, which it stains of a deep violet. 3d. 

 From the flowers of the carthamus tinciorius, on 

 the addition of an alkali, a red extract is obtained, 

 which is precipitated by acids, and forms the 

 beautiful powder called carmine, or rouge. 4. 

 Brazil wood, obtained from the Gesalpina crista, 

 furnishes, with the addition of alum, a red pow- 



der, which dyes stuffs, and affords the lake used 

 in water colours. 6. A red colouring matter is 

 obtained from hemaiosei/lon Oampechianum, or 

 Campechy wood, nearly resembling Brazil wood, 

 except that its shade is somewhat deeper, and 

 more permanent; much used in silk dyeing. Cud- 

 bear, a substance extracted from several species of 

 lichens, affords a beautiful purple dye. Red 

 Sanders wood is soluble in alcohol, and imparts 

 a deep crimson to the fluid. 



Yellow, a very general vegetable colour, is pro- 

 cured from several plants. The resida cuteola of 

 Linnseusyields a yellow by boiling its dried stems, 

 and precipitating with alum. This matter is 

 much used in the dyeing of silks, cottons, and 

 wool. The morns tinctoria, a native of the West 

 India islands, also yields a yellow dye, by decoc- 

 tion of its wood and the addition of the acid. If 

 the bruised seeds of the iixa orellana are made 

 into a paste with a little oil, and boiled in water, 

 a solution of alum wiU throw down a yellow pow- 

 der, well known as anotto. Several other plants 

 yield a yellow dye, as serratula tinctoria, genista 

 tinctoria, rhus cotinus, and rhamnus infectorius. 

 Turmeric is the prepared root of the curcuma 

 longa, a plant which is a native of the East Indies. 



Saffron is a yellow dye obtained from the 

 petals of the crocus satimis, extensively culti- 

 vated in Cambridgeshire. Sumac is obtained 

 from the dried and powdered branches of the 

 rhtis coriaria, a shrub indigenous to Italy and 

 the south of France, where it is cultivated for 

 dying yeUow, and for tanning leathers. 



A brown colouj is produced from a great many 

 vegetables, especially those of an astringent 

 character. It is obtained from the root of the 

 walnut tree and rind of the walnut, from the 

 elder tree and oak, and especially from nutgalls. 

 These last are procured fi'om a species of oak, 

 indigenous to the south of Europe. If a de- 

 coction of powdered galls be added to a solution 

 of sulphate of iron, a deep black is produced, 

 much used as a dye, and also with the addition of 

 a little gum arable, forming the common writing 

 ink. 



Though green is the universal livery of vegetable 

 nature, yet there is no distinct principle which 

 can be used as a green dye. Green is in fact a 

 compound colour, and is always formed by dying 

 substances first yellow and then blue. The 

 green matter of the leaves of plants has been 

 called chromalite. Sap green is the inspissated 

 juice of the half-ripe berries of buckthorn, 

 {rhamnus catharticus) a plant which grows wild 

 in Britain, and other parts of Europe. Alkalies 

 change this sap green into yellow. 



Ta/nnin. If a quantity of pounded nut galls 

 or bruised seeds of the grape, be taken and dis- 

 solved in cold water, and the solution evaporated 

 to dryness, there will be left behind a brittle and 

 yellowish substance of a highly astringent taste, 



