L. TECHNOLOGY. 437 



bath containing a solution of salt of tin completes the process. 

 To this second bath saffranin must be added in sufficient quan- 

 tity to obtain the desired shade. Rinsing is not absolutely 

 necessary, but may be done. The drying succeeds best with 

 moderate heat, 14 (7, CXCIX., 1871, 430. 



AFRICAN KED. 



A new coloring matter has been introduced into England, 

 under the name of African red, which can be used instead of 

 madder, and is quite inexpensive. It is not necessary to pre- 

 pare the fabric with tin, and the color can be readily fixed by 

 the ordinary methods. It can be used equally well for color- 

 ing cotton or silk. 14 C, CC, hi., 245. 



PRODUCTION OF BLUE BRONZE. 



Mr. C. Conrady, of Nuremburg, obtains a brilliant and fast 

 blue bronze color by directly dyeing the white bronze with 

 aniline blue. He boils the white bronze color for several 

 hours in a weak solution of alum, then washes and dries. Be- 

 ing thus prepared, the white bronze is stirred in a solution 

 of aniline blue in alcohol until the desired shade is obtained. 

 After being washed in warm water, it is mixed with some pe- 

 troleum while still moist. The smell of the petroleum is lost 

 by exposure to the air for a few days. 5 (7, 1871, 88. 



SOLVENT OF INDIGO. 



According to the Journal of the Society of Arts, Venice 

 turpentine or paraffine, heated to the boiling point, will dis- 

 solve indigo with the same blue color as a solution of sulphu- 

 ric acid ; in petroleum indigo forms a carmine solution, while 

 in spermaceti it produces a carmine violet, and in stearic acid 

 a blue color. 18 A, August 19, 247. 



BLUE DYE FROM MOLYBDENUM. 



According to late experiments by Professor Bottger, based 

 upon some previous researches of Dr. Schonn, if molybdic 

 acid be dissolved to saturation in concentrated sulphuric 

 acid with heat, an uncolored clear fluid is obtained, forming 

 a double acid of sulphuric and molybdic acid. If a little of 

 this double acid be placed in a porcelain dish and heated till 

 it begins to throw off white vapors, and then a certain quan- 



