M. TECHNOLOGY. 503 



about 18 per cent, by the precipitation of sulphate of baryta 

 (permanent white) in the fibres of the wool in the second 

 bath. 23 0, November 1, 1873, 419. 



ANILINE GREEN ON WOOL. 



According to Lauth, the wool is first to be prepared in a 

 bath to which hyposulphite of soda and an acid, or an acid 

 salt, has been added ; the sulphur precipitated on the wool 

 in this way fitting it to take the aniline color. A tendency 

 of the wool to lose its elasticity, and to become soft and 

 shrink, on account of the penetration of the sulphur into the 

 fibres, may be remedied by adding a small quantity of alum 

 or of zinc salt to the bath. Before treatment with the hypo- 

 sulphite, the wool must be scoured and freed (by means of 

 dilute hydrochloric acid) from any metallic compounds that 

 may have been taken up in spinning or weaving, otherwise 

 brown specks of metallic sulphides may be formed. The dye- 

 ing is accomplished by simply placing it, when well washed, 

 in a solution of aniline green in warm water and gradually 

 raising the temperature to 212. 6 (7, October 9, 1873, 406. 



ECONOMICAL INDIGO COLD-YAT. 



A considerable economy of indigo may be effected, accord- 

 ing to Reimann's Farber-Zeitung, by forming the cold-vat by 

 boiling four pounds of red snunders-wood and eight pounds 

 of catechu with about ten o-allons of water, and dissolvino- 

 two pounds of salt in the liquid. This is to be strained after 

 boiling again, and the clear decoction then poured into the 

 vat, into which, after it is filled sufficiently with water, the 

 indigo preparation is to be introduced. This is composed of 

 twenty-four pounds of sulphate of iron, sixteen pounds of 

 lime, and six pounds of indigo, to be well stirred before al- 

 lowing it to settle for use. 24 C, 1873, xxxvil, 292. 



DYEING ORNAMENTAL FEATHERS BLACK. 



Place them for twenty-four hours in a soda-bath that is not 

 too strong, then rinse well, and place for twelve hours in an 

 eight per cent, solution of nitrate of iron ; rinse well a^ain, 

 and dye with logwood and fustic. If the black appear red- 

 dish, draw the feathers through dilute sulphuric acid, and boil 

 a short time in a weak bath of fustic. 26 C, 1874, 1., 4. 



