1835.] Calico- Printing. 11 



they are dried. This removes the mordants from all those 

 parts to which the acid has heen applied, which of course, 

 remains white after the cloth is dyed. 



2. Tartaric acid thickened with gum, is applied by the 

 block, or cylinder, to cloth previously dyed Turkey-red. 

 It is then passed through an aqueous solution of chloride 

 of lime. The acid disengages chlorine from the chloride, 

 which of course, destroys the colour of those parts to 

 which it had been applied, while all the other parts of the 

 cloth retain their red colour. When oxide of lead is de- 

 posited on the cloth, along with the acid, and the cloth 

 after passing through the aqueous solution of the bleach- 

 ing-powder, is passed through an aqueous solution of 

 bichromate of potash. The parts that would have re- 

 mained white, are converted into a fine yellow. This 

 beautiful process is not confined to Turkey- red. 



3. Protochloride of iron is used to discharge the manga- 

 nese brown, and substitute a buff. This it does, by de- 

 priving the manganese of oxygen, and thus rendering it 

 soluble : (the manganese is made soluble by conversion 

 into chloride of manganese) while the protochloride of iron, 

 being converted into perchloride, deposites peroxide of iron 

 on the cloth, which produces the characteristic buff or 

 orange colours of that oxide. 



Sulphate of iron is used in a variety of ways. It de- 

 oxidizes the indigo in the indigo vat, and renders it soluble 

 in lime-water. It produces gold, buff, 8fc. colours, and 

 makes a good chemical black with logwood. 



4. Protochloride of tin, when applied to cloth dyed brown 

 by the sesquioxide of manganese, immediately deoxidizes 

 it, discharges the colour, and leaves the part white. If it 

 be mixed with Brazil wood, or cochineal, it discharges the 

 manganese, but leaves a pink. When mixed with logwood, 

 it leaves 'djmrple ; and when with Prussian blue, a blue. 



To produce a yellow upon manganese brown, chloride of 

 tin is mixed with sulphate of lead. This mixture thick- 

 ened with roasted starch, is printed on the manganese 

 brown. As soon as it is dry, the manganese being reduced 

 to the state of chloride may be washed off; but the sulphate 

 of lead adheres to the cloth, in consequence of an affinity 

 between them. The cloth being now limed, and passed 



