DYEING AND CALICO PRINTING. 321 



as to expel from them Various substances which, as above stated, inter- 

 fere with the dyeing of the fabrics. 



Purpurine and Green Alizarine. — Messrs. SchaafT andLauth exhi- 

 bited in the French department, most beautiful commercial preparations 

 obtained from madder, and called purpurine and green alizarine ; and as 

 these substances are now applied by continental printers, and as the 

 process for obtaining them (devised by Mr. Emile Kopp, a most eminent 

 chemist) is very interesting, it is deemed advisable to give here a short 

 notice of it. Six hundred pounds of ground madder are allowed to 

 macerate for ten hours in a vat containing 800 to 1000 gallons of a 

 solution of sulphurous acid, and after running off this liquor, the 

 madder is again treated with 200 to 250 gallons of the same acid 

 solution. These liquors are then mixed with three per cent of sul- 

 phuric acid, specific gravity T60, and the whole heated to about 100 deg. 

 by means of steam, when the purpurine separates itself under the form 

 of large red flakes, which, in a few hours settle at the bottom of the vat. 

 The liquors are then run off, and carried to ebullition for three or four 

 hours, when a new substance called green alizarine is liberated and pre- 

 cipitates. Both these products require only washing to be ready for 

 the printer. The dyeing power of these new substances is remarkable, 

 that of purpurine being equal to forty or fifty times the same quantity 

 of madder, and the green alizarine to thirty-eight times that of madder. 

 The 600 lbs. of madder yield about 4 lbs. of purpurine and about 16lbs 

 of alizarine. The madder treated as above described, can be converted 

 into garancine, the dyeing power of which is equal to half that of 

 ordinary garancine. Green alizarine can be employed for the same 

 purposes as commercial alizarine, Purpurine gives magnifieient reds 

 and pinks with alumina mordants, but no purple with iron mordants. 

 Purpurine, however, will probably be chiefly employed as a pigment or 

 in steam printing. 



Printed and Plain Turkey-red Fabrics. — The process for produc- 

 ingTurkey-red on fabrics being identical with that followed for yarns, it is 

 unnecessary to repeat here the details of the process. But besides the 

 intricate and difficult manipulation which Turkey -red goods have to 

 undergo, there is another peculiarity connected with them, viz., the 

 method by which the whites are obtained, which is the reverse of that 

 followed with madder goods, in which the whites are preserved, whilst 

 in the case of Turkey-red the whites are obtained by destroying the 

 colour after it has been fixed. This is done by printing tartaric acid on 

 the cloth, and then bringing it into contact with bleaching liquor (or 

 hypochloric of lime), or by forcing a weak solution of sulphuric acid 

 and bleaching powder through perforated plates, the result being that 

 the red is destroyed on those parts where the acid bleaching liquor has 

 tome in contact with the fabric. 



In conclusion, it should be stated that the business of calico printing 

 VOL. Ill, p !■ 



