WOOL.

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are found in the body of the sheep in that peculiar state. The fibre itself,*after having been treated with water, alcohol, and ether, still contains 0*3 to0-5 per cent of ash, composed of phosphate of lime and magnesia, sulphateand carbonate of lime, silica, and peroxide of iron. The organic substance ofthe fibre, often called keratine, consists of a proteinoid substance, containingor combined with large quantities of sulphur, a considerable proportion ofwhich is readily removed by the action of alkalies. When wool is steeped inplumbite of soda—a solution of oxide of lead in caustic soda—the fibrebecomes coloured black, owing to the formation of sulphide of lead, due tothe sulphur naturally contained in the wool. At 150° F. wool gives off sul-phurous odours ; even during the boiling of wool and woollen fabrics in water—flannel, for instance—an odour of sulphur is perceptible. Hence it followsthat, in dyeingwool with bright colours, contact with metallic surfaces, and thepresence of salts of lead, copper, and tin must be carefully avoided. Especially isthis the case with steam-colours. The intelligent Diredteur de la Manufacturedes Gobelins, at Paris, eliminates the sulphur from the wool used in thatestablishment by soaking the wool for twenty-four hours in milk of lime, atthe ordinary temperature of the air, and then washing the wool in dilutehydrochloric acid, and afterwards in water. It appears, however, that evenwhen this treatment is repeated twenty-eight times, for forty-eight hours eachtime, all the sulphur will not have been eliminated, and there may even thenremain 0*46 per cent of sulphur; but the wool is no longer coloured by conta&with plumbite of soda.

Wool deprived of naturally-adhering grease, and heated to i( 5 o°, assumes ayellow tinge, which is deeper when the wool has previously been de-sulphured.If the wool has not been deprived of the grease adhering to it naturally, itbecomes, when heated to 160 0 , coloured brown. Heated to 130° wool gives offammonia, and, similarly to most protein compounds, wool does not admit ofbeing heated beyond 120 0 , in a current of dry air, without suffering decompo-sition. Schweitzer’s reagent does not aCt upon wool at the ordinary tempera-ture of the air, but it dissolves wool when heat is applied. Chlorine andhyperchlorous acid attack wool at the ordinary temperature, causing it toassume a yellow colour; hence wool and woollen fabrics cannot be bleachedby chlorine. Nitric acid, even when dilute, colours wool yellow, formingxanthoproteic acid: this property is sometimes utilised in the printing ofpatterns upon woollen fabrics, especially such as have previously been dyedblue with indigo, for the nitric acid, in destroying the indigo, gives a deepershade of yellow. Caustic alkalies disintegrate and dissolve wool very rapidly;strong ammonia adts injuriously upon wool, causing it to become rapidly dis-integrated. The solutions of the alkaline carbonates and of soaps, if not tooconcentrated, and if at a lower temperature than 6o°, do not perceptibly affedtwool and its tissues.

When wool is ignited it burns slowly, emitting a very disagreeable odour,similar to that given off by burning horn. A woollen thread held in the flame°f a candle leaves a voluminous coke, which remains hanging at the end ofthe thread. This property is often employed in the detection of woollenfibre.

Wool, especially when roughly washed and purified, is very hygroscopic,a nd though dry to the touch may have absorbed between 7 and 8 per cent ofMoisture. The behaviour of wool towards colouring matters and dyes is