MECHANICS AND USEFUL ARTS. 73 



large surface of land was required. Further, at that time, bleachers had to 

 use potashes imported from Canada; whereas, at the present time, thanks to 

 the progress of chemical knowledge, not only is soda-ash manufactured in 

 this country, but, by the application of bleaching powder, calicoes are much 

 better bleached in twenty-four hours than they were formerly by a six weeks' 

 exposure to the atmosphere; and even when an extra cleaning and whiteness 

 are required, as for madder goods, only two days are necessary. The aid of 

 machinery renders possible the continuous process, that is to say, several 

 hundred pieces of gray calico are sewn together, end to end, and made to pass 

 from one operation to another, without any pause, until they are bleached. 

 So rapid and economical is this method that the cost of bleaching a piece 

 of calico does not exceed one or two pence. Chlorine, again, renders a 

 great service to the calico printer, by enabling him, after his madder goods 

 have been produced and soaped, to obtain fine whites without the necessity 

 of exposing them for several days in the meadows to the action of the at- 

 mosphere. In fact, the discovery of garancine and alizarine, and their appli- 

 cation to calico printing, have facilitated the production of madder styles at 

 very low cost, as the whites of such goods require no soaping, and only a 

 little bleaching or cleaning powder. 



Cotton has this peculiarity, as distinguished from wool and silk, that it will 

 not fix any organic color, excepting indigo, without the interposition of a 

 mordant, which is generally a metallic oxide or salt. The two most impor- 

 tant discoveries in connection with this necessity of calico printing were, 

 first, that made in 18:20, by Mr. George Wood, of Bankbridgc, who found 

 out the means of preparing calicoes with peroxide of tin, which enabled 

 printers to produce a large variety of prints called steam goods; and, sec- 

 ondly, that of Walter Crum, Esq., F. R. S., who, in a paper presented to the 

 British Association, at Aberdeen, in 18-59, showed that the tedious process of 

 ageing madder mordants for three or four days might be dispensed with by 

 passing the goods, during a quarter of an hour, through a moist atmosphere, 

 at a temperature of 80 to 100, where the mordants absorb the required 

 quantity of moisture, and then rapidly undergo the chemical changes neces- 

 sary to fit them for producing the black, purple, lilac, red, pink, and choco- 

 late colors, which the madder root will yield immediately in the dyebeck, 

 according to the nature of the mordant previously fixed in the cloth. 



As it is impossible in the brief space of an hour to convey an idea how va- 

 rious colors are produced on prints, I shall confine my remarks to illustrating 

 the interesting fact that abstruse science has brought to light various tub- 

 stances which have lately proved valuable accessories to the resources of the 

 calico printer. Thus Dr. Prout, some thirty or forty years ago, made the 

 curious discovery that uric acid possessed the property of giving a beautiful 

 red color, when heated with nitric acid, and then brought into contact with 

 ammonia. The substance thus obtained was further examined by Messrs. 

 Liebig and Wohler, in a series of researches which have been considered as 

 amongst the most important ever made in organic chemistry; and this sub- 

 stance they call murexide. In the course of these investigations they also 

 discovered a white crystalline substance, called alloxan. For twenty years 

 both these substances were only to be found in the laboratory; but in 1851, 

 Dr. Saac observed that alloxan, when in contact with the hand, tinged it red. 

 This led him to infer that alloxan might be employed to dye woollens red; 

 and further experiments convinced him that if woollen cloths were prepared 

 with peroxide of tin, passed through a solution of alloxan, and then sub- 



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