264

DYEING AND CALICO PRINTING.

We will now rapidly review the methods which have been employed forobtaining extradts of madder :—

1. Messrs. Robiquet and Colin exhaust their charbon sulfurique either bymeans of a boiling solution of alum, and precipitate the colouring matter withsulphuric acid; or they employ alcohol first, cold, to wash out a resinousgreasy matter, and a deep red-brown liquid not applied for any useful purpose,though the alcohol is recovered. The charbon sulfurique is next exhaustedwith boiling alcohol in a suitable apparatus. In this manner a very concen-trated tindture is obtained, from which the colouring principles are abstractedby the addition of water. The precipitate is separated by filtration, and afterhaving been pressed to remove moisture, is sold under the name of “ Colorin.”The tinctorial value of this substance is equal to seventy times its weightof madder, a result especially due to the treatment with cold alcohol, wherebythe greater part of the resinous matter has been got rid. Garancin as nowmade can be treated in the same way, yielding the same results.

2. M. Kuhlmann treats madder with boiling alcohol, evaporates to the con-sistence of an extradt, which he washes with water to remove the substancessoluble therein. This process is faulty, as it is impossible thus to extradt allthe useful matter from the ground root.

3. MM. Persoz and Gaultier de Claubry exhaust madder—first, with aboiling solution of carbonate of soda, and next, with an alum solution heatedup to ioo°. The sodic solution yields, on saturation with an acid (chlorhydric),a gelatinous precipitate of pedtic acid mixed with colouring matter. Thisprecipitate may be treated with alcohol, which leaves pedtic acid and takes upthe pigments.

4. M. Dandrillon steeps madder in hydrochloric acid, and treats next withboiling alcohol. The filtered liquid is saturated with chalk, concentrated,and precipitated by means of water.

5. M. Colomb steeps madder in dilute nitric acid, and washes the acid outafter some hours. The madder is next submitted to the adtion of caustic sodalye (sp. gr. 1*094= 18 0 Tw.). The violet-coloured alkaline solution is precipitatedv* ith dilute nitric acid, and the ensuing bulky precipitate is well washed andtreated with boiling alum, whereby the colouring matter is taken up and re-precipitated by means of any acid. The solution may also be precipitated bymeans of carbonate of soda, yielding a madder lake.

6. According to M. E. Schwartz, a large portion of the colouring matter ofmadder may be readily extradted from either garancin or -fleur de garance byhot poppy or any other boiling oil. On cooling these oils deposit an extradt,which yields brilliant, fast, and resisting colours.

7. MM. Gerber and Dollfus exhaust fleur de garance with boiling wood-spirit. The concentrated liquors are precipitated with water, yielding 6J percent of a yellowish-brown extradt. The residue of the raw material is adtedupon by a fresh quantity of wood-spirit, acidified with-^th of its bulk ofsulphuric acid. In this way another portion of extradt is obtained almostequal in quantity to the first. This last product has been employed and soldunder the name of azala.

8. MM. Verdeil and Michel operate as follows:—The unground dried root isfirst steeped in water acidulated with sulphuric acid; next broken up by beingsqueezed and torn to shreds by means of fluted rollers. The material thus