INDIGO. 



Carolina and Louisiana avrrajcs 65 

 pounds the acre: in Cuiatimala, 112 

 pounds is ol)taincd on good soils. 

 The low price of labour in India 

 tends to the discouraj^ement of the 

 cultivation of indigo in the United 

 States ; it is, however, raised for 

 plantation purposes. The following 

 is a sketch of the plan in the South 

 for this object, by the Southern Agri- 

 culturist ; it produces an imperfect 

 article, but good enough for the plant- 

 ers' use : 



" Cut the indigo when the under 

 leaves begin to dry, and while the 

 dew is on them in the morning ; put 

 them in a barrel, and fill this with 

 rain water, and place weights on to 

 keep it under water. When bubbles 

 begin to form on the top and the water 

 begins to look of a reddish colour, it 

 is soaked enough, and must be taken 

 out, taking care to wring and squeeze 

 the leaves well, so as to obtain all the 

 strength of the plant ; it must then 

 be churned (which may be done by 

 means of a tolerably open basket, 

 with a handle to raise it up and down) 

 until the liquor is quite in a foam. 

 To ascertain whether it is done 

 enough, take out a spoonful in a 

 plate, and put a small quantity of 

 very strong lye to it. If it curdles, 

 the indigo is churned enough, and 

 you must proceed to break the liquor 

 in the barrel in the same way, by put- 

 ting in lye (which must be as strong 

 as possible) by small quantities, and 

 continuing to churn until it is all suf- 

 ficiently curdled : care must be ta- 

 ken not to put in too much lye, as 

 that will spoil it. When it curdles 

 freely with the lye, it must be sprin- 

 kled well over the top with oil, which 

 immediately causes the foam to sub- 

 side, after which it must stand till 

 the indigo settles to the bottom of the 

 barrel. This may be discovered by 

 the appearance of the water, which 

 must be let off gradually by boring 

 holes first near the top, and afterward 

 lower, as it continues to settle. When 

 the water is all let off, and nothing 

 remains but the mud, take that and 

 put it in a bag (flannel is the best), 

 and hang it up to drip, afterward : 

 418 



' spreading it to dry on large dishes. 



Take care that none of the foam, 



which is the strength of the weed, 



' escapes ; but if it rises too high, sprin- 



; kle oil on it." 



{ Indigo is found in numerous legu- 

 ' minous plants besides the indigofera, 

 as the Baptisia ; it also exists in the 

 Polygonum lincCorium, in species of 

 ncrium and isatis. One plan of dis- 

 covering the presence of this colour- 

 , ing matter in any leaf is to place it 

 in strong ether until the green is ex- 

 tracted, and it becomes white or of a 

 light yellow ; then expose this freely 

 to the air, and if indigo be present, 

 I the colour is changed to blue. 

 I Chemical Observations and Dyeing. 

 — The lumps sold in commerce for 

 indigo are a mixture of several bod- 

 ies, as gluten, or gliadine, brown, red, 

 and blue colours ; lime, and other 

 mineral substances. The proportion 

 of blue colour varies from 19 to 75 per 

 cent., according to the experiments 

 ofUre, the rich purple, violet-coloured 

 samples being best, and the East In- 

 dian generally superior to the Guati- 

 mala. It is insoluble in water, alco- 

 hol, or dilute acids. The blue indi- 

 go sublimes at 554° Fahrenheit, with 

 a purple smoke, and forms purple^ 

 shining scales, but much is destroyed. 

 The sublimed indigo consists of car- 

 bon, 73- 1 ; oxygen, 131 ; nitrogen, 

 10 8 ; hydrogen, 4. Indigogene, ol 

 Crr> Hio N3 O4 . — (Dumas.) 



Indigo is readily dissolved in strong 

 sulphuric acid, seven to eight times 

 the weight of commercial oil of vit- 

 riol being necessary ; this is called so- 

 lution of indigo, sulphate of indigo, 

 Saxon and chemical blue, and is ex- 

 tensively used for dyeing. It may be 

 prepared in quantity and kept, and is 

 sold at the proper stores. To make 

 it, the acid must be placed in an 

 earthen-ware dish, surrounded with 

 water to keep it cool, and the pound- 

 ed indigo added, with stirring, in small 

 quantities ; when it is dissolved, the 

 whole is covered and left for 48 hours ; 

 it is then mixed with twice its weight 

 of pure water, and bottled. This so- 

 lution contains the indigo, red and 

 brown colours, and gluten, and does 



