INDIGO 903 



fracture being dull and earthy. It is sometimes lighter, sometimes apparently heavier 

 than water, this difference depending on its being more or less free from foreign 

 impurities, as well as upon the treatment of its paste in the boiling, pressing, and 

 drying operations. Its colour is blue of different shades ; as light blue, purplish- 

 blue, coppery-blue, and blackish-blue. On being rubbed with the nail, or a smooth 

 hard body, it assumes the lustre and hue of copper. It is usually "a homogeneous 

 mass, but it occasionally contains grains of sand or other foreign bodies, and some- 

 times presents inequalities of colour. It is frequently full of small cavities, which 

 proceeds from the drying process having been conducted too rapidly, and it is also 

 covered at times with a whitish matter consisting of mould. It varies very much in 

 consistency, being sometimes dry, hard, and compact, whilst sometimes it is easily 

 broken into thin flat pieces. Indigo is devoid of smell and taste. When applied to 

 the tongue, however, it adheres slightly, in consequence of the property which it 

 possesses of rapidly absorbing moisture, a property which is often had recourse to 

 in order to ascertain its quality. When thrown on red-hot coals it yields vapours 

 of a deep purple colour, which, when condensed on cold bodies, give shining needles 

 having a coppery lustre. It is insoluble in water, cold alcohol, ether, muriatic acid, 

 dilute sulphuric acid, cold, ethereal, and fat oils ; but boiling alcohol and oils dissolve 

 a little of it, which they deposit on cooling. Creosote has the property of dissolving 

 indigo. 



Indigo varies very much in quality, but it requires much discrimination in order to 

 judge fairly of the quality of any sample from mere inspection and application of the 

 tests usually employed by dealers. A cake of indigo being broken, and the nail or 

 the edge of a shilling being passed with a tolerable degree of pressure over the 

 fractured part, a fine coppery streak will be produced if the indigo is good. If the 

 indigo furrows up on each side of the nail, it is weak and bad, and if the coppery 

 streak be not very bright it is not considered good. When a piece of indigo is 

 broken the fracture should be held up to the sun, and, if it has not been well 

 strained from the dross, particles of sand will be seen glistening in the sun-light. 

 The outside or coat should also be as free from sand as possible. When the squares 

 are broken in the chests the indigo fetches a low price, and if it is very much crushed 

 it is only bought by the consumers for immediate use. The methods employed for 

 ascertaining the true amount of colouring matter in any sample of indigo will be 

 described below. 



Indigo is generally classified according to the various countries from which it is 

 obtained. The principal kinds are the following : Bengal, Oude, Madras, Manilla, 

 Java, Egyptian, Guatemala, Caraccas, and Mexican. 



At the present day the finest qualities of indigo are obtained from Bengal, the 

 produce of that country having now taken the place in public estimation which was 

 once occupied by that of the Spanish colonies. The export of indigo from Bengal, 

 which in 1853 amounted to 120,000 maunds (of 74lbs. 10 oz.) would require for its 

 culture about 1,025,000 acres, and an annual expenditure of 1,300,000^. Of this 

 extent of land about 550,000 acres is believed to be included in the Lower Provinces, 

 and consists chiefly of alluvial lands rescued from the rivers. The best qualities of 

 Bengal indigo are manufactured in the Jessore and Kishenaghaur districts, but each 

 district produces a quality peculiar to itself, and differences of a less striking cha- 

 racter may be perceived in the produce of different factories. The Bengal indigo, 

 when packed in chests, consists of four principal qualities, viz., the blue, purple, 

 violet, and copper. But these kinds, by passing over into one another, produce a 

 number of intermediate varieties, such as purply-blue, blue and violet, purply- violet, 

 &c. The various qualifications would, therefore, be distinguished as follow : 1. Blue. 

 2. Blue and violet. 3. Purple. 4. Purple and violet. 5. Violet. 6. Violet and 

 copper. 7. Copper. The leading London brokers, however, classify Bengal indigo 

 into the following grades : fine blue, fine purple and violet, fine red and violet, good 

 purple and violet, middling violet, middling defective, consuming fine, middling and 

 good, ordinary, ordinary and lean trash. The finest qualities of Bengal indigo present 

 the following characteristics. They consist of cubical pieces, are light, brittle, of a 

 clean fracture, soft to the touch, of a fine bright blue colour, porous, and adhering to 

 the tongue. The lower qualities have a duller colour, assume more and more of a 

 reddish tinge, are heavier, more compact, and less easily broken. 



The indigo from the upper provinces of India comes chiefly from Tyroot, Oude, and 

 Benares. It is inferior to Bengal indigo. 



Of Madras indigo there are two kinds, viz. : 1. Dry leaf, made from dry stacked 

 leaves. 2. Kurpah, which is manufactured from the wet leaf in the same way as 

 Bengal indigo. The latter has only come into use since 1830. Both are of inferior 

 quality to Bengal indigo. 



The Manilla indigos present the marks of the rushes upon which they have been 



