No. 129.] 441 ■ 



When wool is to be d>ed a netting is fastened over as well as 

 under it, to prevent it from coming in contact with either the 

 top or bottom. After being kept in the vat a proper length of 

 time it should be wrung and exposed to the air, when the green 

 color it has imbibed in the vat will be changed almost instanta- 

 neously by absorbing the oxygen of the atmosphere. 



Indigo, a corruption of indicum, India, and gero, to bear. This 

 is an extensive genus, a beautiful plant. Annual and biennial 

 kinds are raised in hot-beds from seed sown in the spring. The 

 flowers resemble somewhat the pea, sufficiently so to class it with 

 the order Leguminosae ; the vexillum is emarginate ; the keil 

 has a subutate spur on both sides ; stamens diadelphous ; style, 

 filiform; legume, continuous ; more than one-seeded; two valved. 

 The cserulea produces tlie best indigo, the argentea, from Egypt, 

 one of the most inferior. The indigo tinctoria not only yields 

 indigo, but is u?ed in medicine. The indigo is considered a 

 cure for liver diseases. All indigo plants contain a green fecula, 

 which when in the green state, is soluble in water ; it attracts 

 oxygen with immense rapidity from the atmosphere, assumes a 

 blue color, and then becomes insoluble. Indigo was known a 

 long time in India as a dye, and was brought from thence to Europe 

 by the Dutch. It is exceedingly valuable for dying, and has a 

 strong affinity for linen, cotton, silk and wool. Every variety of 

 cloth may be dyed with it, without requiring any mordant, the 

 color produced being permanent. There are two ways of dyeing 

 with indigo — one dissolved in sulphuric acid, forming sulphate 

 of indigo ; with this silk and wool are d} ed. The color given 

 is very beautiful, and is called saxon blue. To form this dye, 

 one part of indigo is dissolved in four parts of concentrated sul- 

 phuric acid ; to the solution is added one part of dry carbonate 

 of potash, and this is diluted with eight times its weight of water. 



The other method is to deprive the indigo of oxygen, from 

 which it obtains its blue color, this reduces it to a state of green 

 fecula after which it must be dissolved in water by means of al- 

 kalies, which act upon it at once in that state. If green sulphate 

 of iron, lime and indigo are mixed together in water, the indigo 

 loses its blue color, becomes green and is dissolved. This soluble 

 is used in dyeing linen and cotton. Another method is to mix 



