M. TECHNOLOGY. 501 



the mode of preparation ; some being almost pure blue, with 

 a slight tinge of green, and resembling the light-blue color 

 of the wing feathers of some parrots. Deepening the shade 

 of green in the pigment strengthens the color, but to the 

 same degree impairs its fineness, although it will still surpass 

 in beauty the pure green manganate. The formation of the 

 blue-green compound depends entirely on the alkalinity of 

 the mass, but it is doubtful whether a definite composition 

 corresponds to each color, as the temperature (which should 

 never exceed a bright-red heat) has greatly influenced the 

 color. It is at least certain that the manganate, as well as 

 permanganate of baryta, mixed with about twenty per cent, 

 of hydrate of baryta, will always yield the blue-green pig- 

 ment on ignition. The blue-green color depends entirely 

 upon its basic character; since it first turns green, and is 

 then gradually decomposed, when the powder is placed in 

 weak acids. Baryta pigments are otherwise quite perma- 

 nent ; tolerably strong sulphuric acid does not aifect them 

 for hours, at ordinary temperatures, and boiling potash has 

 practically no effect on the green. In any case, the perma- 

 nence of the blue color is increased by the addition of a little 

 baryta. These pigments seem particularly adapted to fresco- 

 painting, as they appear most brilliant on stone, and espe- 

 cially on lime ; but their preparation is rather expensive. 

 15 (7, 1873, xxiv., 371. 



ALIZARINE RED ON COTTON. 



Although the new alizarine red had been used to a con- 

 siderable extent in dyeing turkey-red, and produces a more 

 beautiful color than madder, its general introduction could 

 not be predicted, since it is more expensive than madder. 

 The discovery of a shorter and cheaper method of producing 

 this pure and beautiful color is claimed by Geyer, by which 

 the operation is completed in about one third the time, at 

 twenty per cent, less cost than the ordinary turkey-red, and 

 without any sacrifice of purity or beauty. 26 (7, 1874, i., 3. 



bastaert's process for drying all kinds of fabrics. 



The following process is said to be applicable to heavy or 

 light goods of cotton, linen, wool, or silk, bleached or un- 

 bleached, printed or dyed. On account of the uniformity of 



