190 DYEING. 



municates an aurora colour to silk, the colour of 

 the annotto is extracted by means of alcali. 



To dye cotton and linen yellow, proceed as fol- 

 lows. Take a sufficient quantity of the acetate of 

 alumine, formed by dissolving one pound of sugar 

 of lead, and three pounds of alum, and the cotton 

 or linen being properly cleansed, immerse it in this 

 mordant (which ought to be blood warm) for two 

 hours, let it be then taken out and moderately 

 pressed or squeezed over a proper vessel, to prevent 

 the unnecessary waste of the mordant, dry it in a 

 stove heat, and soak it again in the aluminous mor- 

 dant; it is then taken out, and again pressed and 

 squeezed as before ; after which, without being 

 rinsed, it is thoroughly wetted in as much, and 

 only as much, lime-water as will conveniently suf- 

 fice for that purpose, and afterwards dried. The 

 soaking in the acetate of alumine may be again re- 

 peated, and if the shade of yellow is required to be 

 very bright and durable, the alternate wetting with 

 lime water and soaking in the mordant may be re- 

 peated three or four times. Thus a sufficient quan- 

 tity of alumine is combined with the cloth, and the 

 combination is rendered more permanent by the 

 addition of some lime. The dyeing both is pre- 

 pared by putting 12 or 18 parts of quercitron bark, 

 (according to the depth of the shade required,) tied 

 up in a bag, into a sufficient quantity of cold water. 

 Into this bath the cloth is to be put, and turned 

 round in it for an hour, while its temperature is 

 gradually raised to about 120, it is then to be 

 brought to a boiling heat, and the cloth allowed 

 to remain in it after that only a few minutes. If 

 it be kept long at a boiling heat, the yellow ac- 

 quires a shade of brown. 



