APPENDIX.

695

Chemical Removal of “ Burls ” from Wool and Woollen Goods.

It is well known that the more powerful mineral acids,—especially the sul-phuric, when diluted with water and aided by the a&ion of heat, attack vege-table matters much more readily than wool. As early as 1853 Fenton andCrom patented the application of this principle for the destruction of cottoncontained in the rags of mixed goods. The following year Izart and Lecouptook out a French patent for the application of the same principle to thedestruction of the “ burls,” i.e. t fragments of cotton, straw, thistle-seeds, andother vegetable matters entangled in wool. These burls, as is well known topractical men, are a source of considerable trouble. As they do not take thesame colours as the wool, they have either to be plucked out of the pieces byhand, with the aid of peculiarly-constructed tweezers, or colour-mixtures—known as “ burling-inks ”—are applied to the spots with a blunt quill, or—asespecially the case with black broadcloths, doe-skins, &c.—the entire pieceshave to be “ burl-dyed,” i.e., submitted to a cotton-dyeing process.

The procedure of Izart, as modified in accordance with the results of expe-rience, consists in steeping the wool, woollen yarn, or pieces, in a bath ofdilute sulphuric acid at 3 C to 4 0 Baume. It is then drained in a centrifugalmachine, and finally heated to ioo c C. in a drying-stove, for a suitable time.The burls are thus destroyed, and the wool, being freed from all residual acidby thorough washing, is submitted to the ordinary manufacturing routine. •

An experimental investigation has recently been carried on by Messrs.Duclaux, Lechartier, and Raulin, as to the limits of time, temperature, andconcentration, within which this procedure is at once safe and efficacious. Ithas been proposed to use baths of earthy and metallic salts, zinc, tin, alum,&c., prior to the acid bath, with the notion of protecting the wool against anycorrosion or alteration of its properties. Carefully executed experimentsproved—as any judicious tinflorial chemist would have anticipated—thatthese additions had not the slightest effeCt in protecting the wool, and exerted,further, a very detrimental aCtion on the subsequent dyeing operations. Avariety of acids and acid salts, both mineral and organic, also chlorine and itsoxygen compounds, were tried in comparison with sulphuric acid. Ihe last-mentioned body, however, was found incontestably preferable.

Drainage in the hydro-extraCtor (centrifugal machine, or “ whizzer ”) wasproved to be quite indispensable. The following table shows the limits oftemperature, time, and concentration of acid, within which the operation can besuccessfully conduCled.

Temperature of Acid for an Exposure of Two Hours Ditto for Half an Hour

Stove. in Stove. m Stove.

8o° C. i£ lit. to 4I lit. (per 100 litres water) 3 to 7 litres.

lit. to 4! lit.1 lit. to ii lit.

iio° C. 1 lit. to 3 lit.

150° C. £ lit. to 1 lit.

Below these limits the burls are not destroyed, whilst above them the woolis attacked, and its affinity for mordants and colours seriously modified. Afterthe stoving, the wool is passed through a weak bath of carbonate of soda,and is then thoroughly rinsed in pure water.

Corallin.

According to the recent investigations of Commaille, corallin is producedbetween 115 0 and 150° C., but more rapidly and plentifully at the latter