364

DYEING AND CALICO PRINTING.

gum, 600 grms.; alum, 60 grms.; oxalic acid, 60 grms.—to this latter some-times a little bichloride of tin is added.

Ammoniacal cochineal, mixed with various other substances, enters into thecompositions used for some colours ; for instance, with orchil, alum, andoxalic acid, in proper proportions, pomegranate-red is produced. With carmineof indigo, alum, and oxalic acid, violet is obtained.

The cochineal colours, especially upon cotton, are fugitive, and do not wearwell. They are affedted by washing, acids, or alkalies ; soap suds and weakalkalies, lime-water, turn the colour to a violet-blue. They are also damagedby perspiration.

Silk [is dyed carmine with cochineal by the following process:—(1), mor-danting in a bath composed of 20 parts of water and £ kilo, of bichloride oftin ; (2), dyeing in a clear bath of cochineal, at a temperature of from 30° to40°, the fabric being worked for about three hours : the shade may be improvedby an addition of ammoniacal cochineal. For scarlet the silk is previouslydyed yellow, with annatto. Silk is dyed ponceau by placing it in a bath pre-pared with 10 kilos, of ammoniacal cochineal dissolved in ten times its weightof water: this mixture is boiled for about ten minutes, and there is added toit, after that, $ kilo, tin crystals, 1 kilo, of cream of tartar, 2$ kilos, of sul-phuric acid, and 2 kilos, tin compound (viz., £ kilo, tin, 1 kilo, hydrochloricacid, and 1 kilo, nitric acid) : the whole mixture is boiled for an hour, decantedafter cooling, and, after the addition of 3 kilos, of safflower, the silk isimmersed in the liquid.

Harmala-Red.

The Syrian rue, known botanically as Peganum Harmala, is a plant growingplentifully in Western Asia and in the South of Russia. From its seeds isextracted a tindtorial principle known as Harmala-red. It is obtained bysteeping the seeds of the plant in alcohol for from eight to fourteen days.The colour has basic properties ; it is insoluble in water, but soluble in ether,and dissolves very readily in absolute alcohol. It combines with acids,forming red salts. Harmala-red dyes up a variety of shades upon wooland silk, from a bright rose to a full scarlet. The most suitable mordantsappear to be the acetate and the sulphate of alumina. The harmala coloursare not very fast. In the seeds of the Syrian rue there are also foundharmaline and harmine, two alkaloids, soluble in acidulated water. Theyhave been examined by several chemists, but have no tindtorial interest.

Erythrose.

Erythrose, or erythrosic acid, is the nzfme given to a tindtorial substanceprepared from the roots of rhubarb, as well the medicinal as the commonkind. It is prepared by digesting the roots, previously cleaned, dried, andsliced, with 4 parts of nitric acid. The residue, which amounts to 8 to 10 percent, dissolves in alkalies with red and purple colours. With the tin andaluminous mordants, erythrose may be made to yield pleasing shades, but ithas never been brought into the market, and, since the discovery of theaniline colours, has been altogether lost sight of. Powdered rhubarb-root,rubbed up with an essential oil (bergamot, aniseed, or fennel) and magnesia,takes a bright rose-colour—a readtion which deserves to be further investigated.