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DYEING AND CALICO PRINTING.

termination is known by the appearance of yellow fumes, which condense inthe cold parts of the apparatus, whilst an alliaceous odour becomes re-cognisable. The maroon-brown matter thus obtained is soluble in water,alcohol, and acids. The aqueous solution is employed at once in dyeing,without preliminary treatment. It may, if required, be purified by precipita-tion with common salt. The so-called naphtha-brown is merely the crudemelt from the manufacture of magenta, containing consequently the secondaryproducts and undecomposed aniline. Sieberg prepares a brown from thecolouring matters precipitated from the mother-liquors resulting from themanufacture of magenta. He heats i part of hydrochlorate of aniline up tothe point of fusion, and adds then £ part of the colouring matter just men-tioned, the apparatus being set in a sand-bath until the brown colour is deve-loped. The product is mixed with 2 parts of carbonate of soda crystals and25 litres of hot water, and is well stirred and mixed up. The solution is thendecanted, and the brown is repeatedly washed with water. In this state itpresents the appearance of a brownish-black tarry mass : 5 kilos, of this crudemass are dissolved in 45 litres of alcohol ; 65 litres of water are added, withconstant stirring. The clear liquid, after settling, is ready for use.

Another brown colour is met with in commerce, obtained by causing metallictin and hydrochloric acid to read upon binitro-benzine, and treating theresulting mass with an alkaline or metallic nitrite.

Schultz prepares a garnet-brown by causing hyponitric acid to read upon asalt of rosaniline. A variety of brown matters may be obtained by oxidisingrosaniline or leukaniline by means of chlorate of potassa, peroxide of lead,bichromate of potassa, &c.

Jacobsen’s brown is made by introducing into a capacious flask 1 part ofpicric acid and 2 parts of commercial aniline. The mixture heats, and thepicric acid dissolves to a thick liquid of an orange-yellow, a result which ispromoted by stirring and the application of a gentle heat. When the tem-perature is raised to no 0 to 120° the mass grows brown, and throws offabundant vapours. To avoid boiling over, the temperature is kept at 140°, orat the utmost not above 160 0 C., for some hours, as long as ammoniacal fumesare given off. The process is at an end when a small portion taken out of theflask and thrown into water gives only a very feeble yellow tint to the liquid.The black mass is then poured, with constant stirring, into water stronglyacidulated with hydrochloric acid, and boiled repeatedly in successive portionsof water to remove any undecomposed aniline. It is still better to grind upthe mass before allowing it to boil, and again after the liquid has cooled, tofacilitate the removal of a red colouring matter. The residue, after boiling, iscollected upon a filter, and well washed, first in a dilute solution of soda, andthen in pure water. If the temperature has not been raised too high, the massis entirely soluble in alcohol. For use it is dissolved in alcohol, acidulatedwith sulphuric acid and mixed with glycerine. It dyes silk and wool withoutmordant, the former a Corinth red, and the latter a black-brown with a violetreflection.

The crude colour may also be purified by adding it to concentrated sul-phuric acid. After some time the sulphuric solution is poured into water,and the pure colour is precipitated by the addition of common salt. In thisstate it is more readily soluble in alcohol.