430 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



indeed, alone constitutes its characteristic mark, is, theoretic- 

 ally considered, independent of its chemical composition, and 

 is rather brought about by the optical relationships of the con- 

 stituent particles. Practically, however, this chemical com- 

 position is of the utmost importance, as affecting the excel- 

 lence of so beautiful and durable a color. Ultramarine, in 

 fact, optically considered, consists of a white and brown mass, 

 in which sulphide of aluminium is mingled in molecular dis- 

 tribution. Each molecule of this combination is found, we 

 may say, inside of a molecule of clay, and at the same time 

 surrounded by three simultaneously developed molecules of 

 sodium, which combine with silica into a basic salt, and en- 

 velop the entire group. 14 (7, c, 299. 



EXTRACTION OF ANILINE DYES FEOM FABRICS. 



Among the problems connected with the art of dyeing, one 

 of much importance is the best method of extracting aniline 

 colors from cloths without injuring the fabric, especially those 

 which it is desired to dye anew ; and to solve this, Dr. Rei- 

 mann, an eminent authority on these subjects, publishes a de- 

 tailed paper in his Dyers' Journal. 



For this end several methods present themselves, the first 

 referred to being the use of chlorine, which, however, is only 

 applicable to cotton, this agent, whether in the form of gas 

 or of chloride of lime, being excluded when we have to deal 

 with substances consisting principally or partially of wool. 

 The simplest method of accomplishing the object in this in- 

 stance consists in digesting the fabrics for a sufficient length 

 of time in alcohol of 90 per cent., which usually completes the 

 decolorization in a short space of time. The same alcohol can 

 be used several times in succession, and can afterward be pu- 

 rified by rectification or redistillation, so as to involve but lit- 

 tle loss. The work is best done in a well-covered copper ket- 

 tle, which is to be set in boiling water. A little hydrochloric 

 acid may be added if the articles are not too delicate, thereby 

 increasing the solubility of the aniline colors. 



Still a third method is based upon the fact that all the 

 aniline colors pass into given uncolored combinations when 

 brought into contact with hydrogen. Thus fuchsin red is al- 

 most immediately decolorized when hydrogen is developed 

 in its solution the same taking place with violet, blue, and 



