Cold vats

—The copperas or common blue vat of this country is so named because the indigo is reduced by means of the protoxide of iron. This salt should therefore be as free as po ible from the red oxide, and especially from any sulphate of copper, which would re-oxidize the indigo. The nece ary ingredients are: copperas (green sulphate of iron), newly slaked quicklime, finely ground indigo, and water; to which sometimes a little potash or soda is added, with a proportional diminution of the lime. The operation is conducted in the following way: the indigo well triturated with water or an alkaline lye, must be mixed with hot water in the preparation vat, then the requisite quantity of lime is added, after which the solution of copperas must be poured in with stirring. Of this preparation vat, such a portion as may be wanted is laded into the dyeing vat. For one pound of indigo three pounds of copperas are taken, and four pounds of lime (or 1 of indigo, 2 1 ⁄ 2 of copperas, and 3 of lime). If the copperas be partially peroxidized, somewhat more of it must be used. A vat containing a considerable exce of lime is called a sharp vat, and is not well adapted for dyeing. A soft vat, on the contrary, is that which contains too much copperas. In this case the precipitate is apt to rise, and to prevent uniformity of tint in the dyed goods. The sediment of the copperas vat consists of sulphate of lime, oxide of iron, lime with indigo brown, and lime with indigo blue, when too much quicklime has been employed. The clear, dark wine yellow fluid contains indigo blue in a reduced state, and indigo red, both combined with lime and with the gluten of indigo di olved. After using it for some time the vat should be refreshed or fed with copperas and lime, upon which occasion, the sediment must first be stirred up, and then allowed time to settle again, and become clear. For obtaining a series of blue tints, a series of vats of different strengths is required. Linen and cotton yarn, before being dyed should be boiled with a weak alkaline lye, then put upon frames or tied up in hanks, and after removing the froth from the vat, plunged into, and moved gently through it. For pale blues, an old, nearly exhausted vat, is used; but for deep ones, a fresh nearly saturated vat. Cloth is stretched upon a proper square dipping frame made of wood, or preferably of iron, furnished with sharp hooks or points of attachment. These frames are suspended by cords over a pulley, and thus immersed and lifted out alternately at proper intervals. In the course of 8 or 10 minutes, the cloth is sufficiently saturated with the solution of indigo, after which it is raised and suspended so as to drain into the vat. The number of dippings determines the depth of the shade; after the last the goods are allowed to dry, taken off the frame, plunged into a sour bath of very dilute sulphuric or muriatic acid, to remove the adhering lime, and then well rinsed in running water. Instead of the dipping frames some dyers use a peculiar roller apparatus, called gallopers , similar to what has been described under Calico Printing ; particularly for pale blues. This cold vat is applicable to cotton, linen and silk goods. When white spots are to appear upon a blue ground, resist pastes are to be used, as described under Calico Printing . The urine vat is prepared by digestion of the ground indigo in warmed stale urine, which first dis oxygenates the indigo, and then di olves it by means of its ammonia. Madder and alum are likewise added, the latter being of use to moderate the fermentation. This vat was employed more commonly of old than at present, for the purpose of dyeing woollen and linen goods. The mode of making the china blue dye has been described under Calico Printing ; as well as the pencil blue , or blue of application. A blue dye may likewise be given by a solution of indigo in sulphuric acid. This proce was discovered by Barth, at Gro enhayn in Saxony, about the year 1740, and is hence called the Saxon blue dye. The chemical nature of this proce has been already fully explained. If the smoking sulphuric acid be employed, from 4 to 5 parts are sufficient for 1 of indigo; but if oil of vitriol, from 7 to 8 parts. The acid is to be poured into an earthen-ware pan, which in summer must be placed in a tub of cold water, to prevent it getting hot, and the indigo in fine powder, is to be added with careful stirring, in small succe ive portions. If it become heated, a part of the indigo is decomposed, with the disengagement of sulphurous acid gas, and indigo green is produced. Whenever all the indigo has been di olved, the ve el must be covered up, allowed to stand for 48 hours, and then diluted with twice its weight of clear river water. The undiluted ma has a black blue colour, is opaque, thick, attracts water from the air, and is called indigo composition or chemic blue . It must be prepared beforehand, and kept in store. In this solution, besides the cerulin , there are also indigo-red, indigo-brown, and gluten, by which admixture the pure blue of the dye is rendered foul, a uming a brown or a green cast. To remove these contaminations, wool is had recourse to. This is plunged into the indigo previously diffused through a considerable body of water, brought to a boiling heat in a copper kettle, and then allowed to macerate as it cools for 24 hours. The wool takes a dark blue dye by absorbing the indigo-blue sulphate and hyposulphite, while at the same time the liquor becomes greenish blue; and if the wool be left longer immersed, it becomes of a dirty yellow. It must therefore be taken out, drained, washed in running water till this runs off colourle , and without an acid taste. It must next be put into a copper full of water, containing one or two per cent. of carbonate of potash, soda, or ammonia (to about one third the weight of the indigo), and subjected to a boiling heat for a quarter of an hour. The blue salts forsake the wool, leaving it of a dirty red brown, and dye the water blue. The wool is in fact dyed with the indigo red, which is hardly soluble in alkali. The blue liquor may now be employed as a fine dye, po e ed of superior tone and lustre. It is called distilled blue and soluble blue . Sulphuric acid throws down from it the small quantity of indigo red, which had been held in solution by the alkali. When wool is to be dyed with this sulphate of indigo blue, it must be first boiled in alum, then treated with the blue liquor, and thus several times alternately, in order to produce an uniform blue colour. Too long continuance of boiling is injurious to the beauty of the dye. In this operation the woollen fibres get impregnated with the indigo-blue sulphate of alumina. With sulphate of indigo, not only blues of every shade are dyed, but also green, olive, gray, as also a fast ground to logwood blues; for the latter purpose the preparatory boil is given with alum, tartar, sulphates of copper and iron, and the blue solution; after which the goods are dyed up with a logwood bath containing a little potash. Statistical Tables of Indigo ; per favour of James Wilkinson, Esq., of Leaden hall-Street. East India Indigo. | Years. | Produce in India. | Con- sumption of World; average, 4 years. | Stock in England 31st De- cember. | Highest Price. | Good middling Violet. | | Per lb. | | | Chests. | Chests. | Chests. | | s. | d. | s. | d. | s. | d. | | 1811 | 21,000 | 22,200 | 26,900 | | 10 | 6 | 5 | 6 | 6 | 0 | | 1812 | 23,500 | 22,500 | 29,500 | | 11 | 6 | 6 | 9 | 7 | 3 | | 1813 | 22,800 | 22,800 | 24,500 | | 15 | 5 | 9 | 0 | 9 | 6 | | 1814 | 28,500 | 23,000 | 24,900 | | 13 | 0 | 7 | 9 | 8 | 3 | | 1815 | 30,500 | 23,200 | 30,400 | | 11 | 0 | 6 | 9 | 7 | 6 | | 1816 | 25,000 | 26,900 | 25,700 | | 10 | 0 | 5 | 0 | 5 | 6 | | 1817 | 20,500 | 27,000 | 23,500 | | 10 | 0 | 7 | 3 | 7 | 9 | | 1818 | 19,100 | 26,500 | 24,000 | | 9 | 3 | 6 | 9 | 7 | 3 | | 1819 | 20,700 | 26,400 | 19,700 | | 8 | 6 | 5 | 6 | 6 | 0 | | 1820 | 27,200 | 24,200 | 14,500 | | 9 | 0 | 6 | 3 | 6 | 9 | | 1821 | 21,100 | 25,300 | 9,800 | | 11 | 6 | 8 | 6 | 9 | 0 | | 1822 | 25,700 | 26,000 | 8,200 | | 12 | 0 | 9 | 0 | 9 | 6 | | 1823 | 29,800 | 25,300 | 13,100 | | 10 | 0 | 7 | 3 | 7 | 9 | | 1824 | 24,100 | 26,500 | 12,200 | | 15 | 0 | 12 | 0 | 12 | 6 | | 1825 | 43,500 | 23,500 | 16,400 | | 15 | 6 | 12 | 0 | 12 | 6 | | 1826 | 28,000 | 27,300 | 22,300 | | 11 | 3 | 7 | 6 | 7 | 9 | | 1827 | 45,300 | 28,900 | 22,800 | | 12 | 6 | 8 | 0 | 8 | 6 | | 1828 | 30,000 | 31,000 | 31,100 | | 10 | 0 | 6 | 3 | 6 | 6 | | 1829 | 43,200 | 33,000 | 31,200 | | 8 | 9 | 5 | 3 | 5 | 9 | | Years. | | | | 1830-1 | 32,100 | 32,800 | 37,600 | 1831 | 7 | 9 | 4 | 3 | 4 | 9 | | 1831-2 | 32,500 | 34,500 | 35,700 | 1832 | 6 | 3 | 4 | 3 | 4 | 6 | | 1832-3 | 35,200 | 35,500 | 32,500 | 1833 | 6 | 0 | 4 | 2 | 4 | 4 | | 1833-4 | 27,100 | 34,600 | 35,800 | 1834 | 8 | 0 | 6 | 3 | 6 | 6 | | 1834-5 | 30,500 | 33,800 | 29,319 | 1835 | 7 | 0 | 5 | 3 | 5 | 6 | | 1835-6 | 32,600 | 34,700 | 21,449 | 1836 | 6 | 3 | 4 | 9 | 5 | 0 | | 1836-7 | - - | 32,600 | 26,219 | 1837 | 8 | 9 | 6 | 9 | 7 | 0 | East India and Spanish , . Indigo . | Years. | Importations. | Exported. | Home Consump- tion. | | East India. | Spanish, . | | lbs. | lbs. | lbs. | lbs. | | 1785 | 154,291 | 1,539,218 | 584,885 | | | 1786 | 253,345 | 1,724,945 | 466,696 | | | 1787 | 364,046 | 1,514,784 | 502,800 | | | 1788 | 622,691 | 1,473,920 | 445,857 | | | 1789 | 371,469 | 1,594,618 | 673,630 | | | 1790 | 531,619 | 1,307,088 | 821,131 | | | 1791 | 465,198 | 1,141,589 | 870,185 | | | 1792 | 581,827 | 1,274,538 | 880,951 | | | 1793 | 890,766 | 1,066,817 | 929,707 | | | 1794 | 1,403,650 | 1,487,642 | 1,623,908 | | | 1795 | 2,862,684 | 1,424,941 | 1,387,171 | | | 1796 | 3,897,120 | 680,915 | 1,883,320 | | | 1797 | 1,754,233 | 535,845 | 3,105,610 | | | 1798 | 3,862,188 | 192,060 | 1,718,624 | | | 1799 | 2,529,377 | 512,459 | 2,585,755 | | | 1800 | 2,674,317 | 1,076,417 | 2,586,833 | | | 1801 | 2,123,637 | 827,696 | 2,281,812 | | | 1802 | 2,264,199 | 669,679 | 1,961,346 | | | 1803 | 2,632,110 | 522,825 | 1,130,194 | | | 1804 | 2,765,871 | 395,258 | 1,523,095 | | | 1805 | 4,666,292 | 687,319 | 1,845,035 | | | 1806 | 2,612,181 | 319,394 | 2,904,614 | | | 1807 | 5,326,032 | 715,809 | 2,006,463 | | | 1808 | 5,314,860 | 477,625 | 1,568,351 | | | 1809 | 2,179,083 | 674,048 | 3,179,861 | | | 1810 | 5,243,613 | 883,061 | 2,485,679 | | | 1811 | 4,453,932 | 658,577 | 1,566,056 | | | 1812 | 4,461,793 | 354,171 | 1,853,916 | | | 1813 | Accounts destroyed by Fire at Custom House. | | | 1814 | 6,803,064 | 328,881 | 5,501,851 | 3,406,282 | | 1815 | 5,543,852 | 79,253 | 4,278,674 | 2,774,091 | | 1816 | 7,247,227 | 39,275 | 4,214,454 | 1,899,819 | | 1817 | 5,001,280 | 134,313 | 2,427,443 | 2,377,659 | | 1818 | 5,497,768 | 187,257 | 2,963,462 | 2,302,163 | | 1819 | 3,689,052 | 129,682 | 3,126,739 | 2,033,601 | | 1820 | 4,924,222 | 161,164 | 4,378,857 | 2,288,196 | | 1821 | 3,943,592 | 119,517 | 2,985,364 | 1,959,509 | | 1822 | 2,549,284 | 374,230 | 2,378,948 | 2,004,062 | | 1823 | 6,557,296 | 664,408 | 2,783,504 | 2,322,221 | | 1824 | 4,595,707 | 485,110 | 2,795,740 | 2,493,350 | | 1825 | 6,233,335 | 560,296 | 3,870,929 | 2,381,233 | | 1826 | 7,699,439 | 386,312 | 4,365,163 | 1,901,047 | | 1827 | 5,404,811 | 662,936 | 3,315,675 | 2,399,365 | | 1828 | 9,683,626 | 229,384 | 4,588,658 | 3,064,915 | | 1829 | 5,978,527 | 769,757 | 4,286,605 | 2,113,830 | | 1830 | 7,920,924 | 295,516 | 4,686,784 | 2,676,945 | | 1831 | 7,004,510 | 290,089 | 4,374,241 | 2,490,134 | | 1832 | 6,221,725 | 131,340 | 5,346,725 | 2,395,653 | | 1833 | 6,304,016 | 331,016 | 3,664,814 | 2,323,300 | | 1834 | 3,798,144 | 357,152 | 3,928,226 | 2,447,827 | | 1835 | 3,986,233 | 183,480 | 4,074,598 | 2,606,772 | | 1836 | 6,753,898 | 418,800 | 3,691,951 | 2,864,274 | | 1837 | 5,872,601 | 673,270 | 3,587,561 | 2,240,451 |