M. TECHNOLOGY. 499 



cheaper and more economical rate than the hyposulphite or 

 sulphite. The excellent effect of the bisulphite solution, acid- 

 ified with sulphuric acid, in bleaching and washing wool, is 

 known, and also the beauty and liveliness of the colors after- 

 ward taken in dyeing. 15 <?, 1873, 177. 



METHYL VIOLET OX WOOL. 



For ten pounds of wool, boil one ounce of methyl violet in 

 a soap-bath, prepared by boiling one quarter of a pound of 

 washing soap, and dye the articles at 158. To produce a 

 bluer shade, first dye in a bath of methyl violet alone, at 140 

 to 158, and then boil for a quarter of an hour in a soap-bath 

 of a quarter of a pound of soap. The wool, however, in this 

 case must be dyed a few shades darker, since the soap-bath 

 renders the color lighter. The color obtained in this way is 

 a tolerably pure and very lively blue. A desired shade may 

 also be produced by boiling the wool for half an hour in a 

 bath of three pounds of Glauber's salt, a quarter of a pound 

 of sulphuric acid, and one ounce of methyl violet. 26 C, 

 1874,1., 2. 



EXTRACT OF SUMAC. 



According to Reimann's Fcirber-Zeitimg, extract of sumac, 

 obtained by boiling and evaporating in a vacuum, has recent- 

 ly been brought into commerce in the form of a thick sirup, 

 which is without any trace of acidity, and which will keep 

 indefinitelv : while the common decoction of sumac soon turns 

 sour and becomes useless. The chief advantage in the use 

 of the extract lies in the economy of time and room, since it 

 simply requires dilution with hot water. The weight of ex- 

 tract, for any shade, can also be accurately determined, and 

 it can be conveniently employed in many cases to produce a 

 desired shade by subsequent additions to the bath, and may 

 often be found of value in dyeing, although possibly too ex- 

 pensive for general use. 14 C, 1873, CCX., 316. 



BARYTA GREEN, OR MAXGANATE OF BARYTA. 



Experiments were made by Fleischer to discover a more 

 direct method for the preparation of the pigment manganate 

 of baryta, or baryta green of greater purity and beauty than 

 that introduced into the market under the name of Rosen- 



