6go

DYEING AND CALICO PRINTING.

dry, the goods are passed through a boiling bath containing I lb. preparedchalk to every io lbs. of cotton, and washed twice: I to i| lb. of cochinealis extracted in water, the bath is heated to 122 0 F. with the addition of a littleflavin, and the goods are worked therein, the temperature being slowly raisedto the boiling-point.

Method of Determining Anthracen.

Dissolve 1 grm. of the sample of commercial anthracen in question in 45 cubiccentimetres of glacial acetic acid, at the boiling-point, in a small flask. Thesolution, if needful, is filtered while boiling, and a solution of ro grms. ofchromic acid in 5 cubic centimetres of water and 5 cubic centimetres ofglacial acetic acid, the liquid being kept at a gentle boil. The addition ofthis mixture is continued till a distindt and permanent yellowish-green colourappears, or till, after prolonged boiling, a drop of the liquid placed upon aclean silver coin produces a reddish spot. The whole is then diluted with150 cubic centimetres of water, filtered after standing some hours, and theprecipitate (chinon) is washed upon the filter, first with water, then with hotand very dilute potash-lye, and then again with water. It is next dried at212 0 F., and weighed. After weighing, the chinon is removed from the filter,and the latter is weighed again. Thus the nett weight of the anthrachinonis obtained, to which o'oi grm. must be added, that quantity having beendissolved and removed by the above-diredted quantity of acetic acid and water.Commercial chromic acid, it must be remembered, often contains lead.

New Class of Colouring Matters.

Croissant and Bretonniere have patented a process for converting certainorganic bodies into colouring matters. The process is applicable not merelyto tannin, aloes, starch, and horn, which have a certain value, but to wasteworthless bodies, such as moss, cellulose, sawdust, humus from decayed wood,&c. The principle employed is the dehydrogenation of the bodies by theadtion of sulphur at an elevated temperature, which the authors believereplaces the hydrogen. If it is required to convert bran into colouring matterit is placed in a small iron vessel, covered with a lid. Caustic soda and flowerof sulphur are added in certain proportions, and the whole is made up into anhomogeneous paste. The vessel is then placed in a furnace where it can beheated to 250° to 300° C. Sulphuretted hydrogen is given off in abundance.When the mixture is dry we find in the vessel, after cooling, a black, friablematter, perfedtly soluble in water, to which it imparts a fine sap-green. Thesolution has a strong affinity for fibres, which it dyes without a mordant.One and the same body gives various tones of colour, according to the propor-tions of the mixture and the temperature applied. Certain substances—suchas extradts of dye-woods, aloes, &c.—are converted at boiling-point, whilstwoody fibre, bran, &c., require a higher temperature.

The following examples may be useful:—

1. Aloes.

Soda-lye, at 40° Baumd

Water.

Flower of sulphur

3 kilos.10 litres.10 ,,

3 kilos.