420

DYEING AND CALICO PRINTING.

true composition of curcumin known.* It is very probable that the phenomenaof colouration as exhibited by curcumin, which turns red and blue, and thenyellow again, under the a&ion of comparatively weak reagents, bear arelation to certain phenomena observed with flowers.

It is not impossible that the roseocyanin of M. Schlumberger is identicalwith the red colouring matter of flowers or cyanin investigated by MM. Fremyand Cloez, which latter substance is turned also blue by alkalies. If this sug-gestion proves correct, on more precise investigation, turmeric could become auseful source of preparation of the red colouring matter of flowers, which it isvery difficult to obtain by diredt extraction.

Although turmeric is rich in colouring matter, its want of permanence is ahindrance to its application as.a dye-material. Some time back the use ofturmeric was almost exclusively limited to printing and dyeing silks. It isnow employed to a vast extent in stuff-dyeing, forming an important consti-tuent in certain compound colours, especially the so-called 44 sour browns.”

Turmeric is generally sold in powder, and is sometimes sophisticated withcommon salt, which gives it a brighter appearance in the mass, but interfereswith its uses. It should be quite dry; if damp it loses its colour, turns ayellowish-brown, and dyes flat shades. The safest method of testing samplesis to dye equal weights of white woollen cloth with equal weights of the tur-merics. The swatches are then compared, not only for depth of colour, butare held up horizontally to the light and viewed along the surface. In this44 over-hand ” position a good turmeric should show a beautiful golden lustre,on the purity of which its value depends for many purposes, i.e n for yellowson the cotton warps of figured table-covers. In India it is used for colouringrice. It serves to make the well-known yellow test-paper for chemical use.The Chinese use kiang-hoang (the vernacular for turmeric) for dyeing silkyellow ; it is the cheapest yellow dye, but of course very fugitive. The dyeingprocess is done as follows :—The pulverised turmeric is treated with boilingwater, and the mixture well stirred up ; the fluid, having become clear, is de-canted from the dregs, and in the fluid the silk is immersed after addition oflime-juice.

The colouring matter of turmeric fixes dire&ly upon wool, silk, and cotton,it being only required to put the tissue in a boiling deco&ion of the ware. Byprinting on tissues an alcoholic or acetic solution of curcumin, and steaming,the colour is also fixed.

M. Persoz has obtained good results by mixing an emulsion of carbonate ofsoda and Gallipoli oil with a solution of curcumin in Gallipoli oil, and usingthis mixture for printing. After drying, the fabrics are passed through anacid. When a pattern is printed on silk by means of an aluminous and aniron mordant, und the silk so prepared first put in a dye-beck containingBrazil wood, and next in a turmeric bath, the patterns will come out red andblack upon a yellow ground.

We now turn our attention to the recently-made researches on curcumin byM. F. W. Daube.f This author has succeeded in preparing pure and crystal-line curcumin by the following process :—The root, coarsely pulverised, is firstsubmitted to a process of steaming, to get rid of the essential oil; it is next

* “ Bulletins de la Societe Chimique de Paris,” 2nd series, vol. v., p. 194.

■f “ Berichte der Deutschen Chemischen Gesellschaft zu Berlin,” third year, p. 609 an ^following.