176 AGRICULTURE AND FORESTRY. 



acid, it gives a rich deposit of almost pure indigo-blue. More 

 colouring-matter is obtained by this method than with an equal 

 amount of woad- leaves, or pastil-leaves (from I satis tinctoria). 



Indican, Indigo-chromogen, was produced by Schunk as follows: 

 The alcoholic extract from dried and pulverized Polygonum-leaves 

 was allowed to evaporate till only a brown fluid remained. This 

 he poured off from its sediment and mixed with a solution of sugar 

 of lead. This gave him a muddy yellow precipitate of chlorophyll, 

 and other impurities, and after filtration a clear yellow fluid, to 

 which he added basic acetate of lead — lead-vinegar. The pale 

 yellow deposit thus produced was separated by filtration from the 

 fluid, edulcorated with water and spirits, and dissolved in an- 

 hydrous alcohol, and then a stream of carbonic acid directed 

 through it. The fluid after a short time became yellow, and 

 white-lead was separated from it. Then followed filtration and 

 the addition of sulphide of hydrogen, to cause a further precipi- 

 tation of lead. After another filtration Schunk allowed it to 

 evaporate, and there remained a syrup, which, when treated with 

 ether, yielded indigo. 



The qualitative reactions of this indigo-producing stuff are 

 exactly the same as those of Indican from leaves of Isatis tinctoria. 

 It is a yellow, transparent syrup, which displays little inclination 

 toward crystallization, and is soluble in water, alcohol, and ether. 

 Its aqueous solution has a more or less acid reaction, takes on a 

 deep yellow colour with caustic alkali, and gives a light yellow 

 precipitate with basic acetate of lead. When the aqueous solution 

 is mixed with a little sulphuric or hydrochloric acid and allowed 

 to stand quiet, indigo after a time separates, sinking to the bottom 

 and forming a scum on the surface, as is also the case with Indican 

 from Isatis tinctoria. 



Schunk proved by these investigations that neither free indigo 

 nor its hydrate (reduced indigo, indigo-white), but only indican are 

 present in dyer's knotweed, thus disposing of Joly's assumption of 

 the contrary. 



2. Carthamus tinctorius, L., Jap. Beni, Beni-no-hana, common 

 saw-wort, or the safflower. This is an annual. In its stiff stalk, 

 branching upwards, and its big, round, yellow blossoms, it resembles 

 Inula ; in its stemless prickly leaves it resembles thistles, belong- 

 ing, like both of them, to the great family of the composites, and 

 following Centaurea in system. The plant attains a height of 50 to 

 100 cm. and yields in its blossoms (separated from the calyx) the 

 well-known safflower, or Spanish red, besides a yellow dye-stuff. 

 India (which is thought to be its original home) and Persia and 

 Egypt have been distinguished in its cultivation from of old, and 

 to this day they supply the world with the greater portion of its 

 safflower. We know now for certain that the saw-wort was raised 

 in Egypt more than 3,500 years ago, since Schweinfurth recognised 

 it in the garland which Brugsch and Maspero, in 1881, found in 



