308 DYEING AND CALICO PRINTING. 



for their application. It is not intended in tins short report to give a 

 description of the numerous methods adopted to produce these new 

 dyes, but only to mention those which are illustrated in the Exhibi- 

 tion by their application to fabrics. 



Since 1851 and even since 1855, a most valuable improvement has 

 been made in the manufacture of an important dye-stuff known under 

 the name of orchil. Though this material yielded beautiful purple and 

 violet dyes, they had the disadvantage of being extremely fugitive, the 

 ■ acid vapours of our large cities causing them to become red, and to fade 

 rapidly. But the important desideratum of giving fastness to these bril- 

 liant colours was obtained in 1856 by M. Manias, of the firm of Guinon, 

 Marnas, and Bonnet, who arrived at this valuable residt by treating 

 lichens, as suggested by Dr. Stenhouse, with milk of lime, filtering off 

 the lime liquor, and precipitating the colour-giving principles from it 

 with hydrochloric acid, gathering these on a filter, and after having pro- 

 perly washed them, dissolving them in caustic ammonia, and keeping 

 this ammoniacal liquor at a temperature of 153° to 160° for twenty to 

 twenty-five days. Under the influence of that temperature the colour- 

 giving principles fix ammonia and oxygen, and are transformed into a new 

 series of products which M. Marnas separates from the coloured liquor 

 by adding chloride of calcium, causing a fine purple lake to be deposited, 

 this, after being well washed and dried, is sold under the name of 

 French purple. It is easy to understand that the chloride of calcium 

 can be replaced by salts of alumina, tin, &c. What distinguishes this 

 orchil colour from those previously known is, that it dyes animal fibres 

 with greater facility than the common orchil, that it gives directly 

 mauve colour's, which can be modified with carmine of indigo, roseine, 

 &c. ; but the essential difference between these purples and those from 

 common orchil is — that while the latter are destroyed by acids and 

 light, those of M. Marnas, on the contrary, withstand these influences. 

 To dye silk or wool with French purple it is simply necessary to to mix 

 the lake with its weight of oxalic acid, boil with water, and then filter, 

 the oxalate of lime remaining on the filter while the colour passes into 

 the filtrate. This liquor is then added to a slightly ammoniacal liquor, 

 contained in the dye-beck, and all that is now necessary is to dip in the 

 beck silk, wool, cotton mordanted with albumen, or cotton prepared as 

 for Turkey-red, when any of these materials will become dyed with 

 magnificent fast shades of purple or mauve. 



It is to be regretted that there is not a larger number of examples of 

 fabrics dyed with a most splendid colour, viz., murexide, or Roman 

 purple, which was so extensively used in 1 856 and 1857 by some of our 

 largest dyers and printers. As this colour furnishes one more remark- 

 able instance of the great assistance derived by practical art from the 

 researches of science, I cannot refrain from giving here a short sketch 

 of its history. In 1776, the illustrious Swedish chemist Scheele, dis- 



