500 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



stiels or Cassel green. As a result, he recommends a differ- 

 ent method, and calls attention to a superior blue-green man- 

 ganate. In regard to the two methods of preparation al- 

 ready published, he states that the one by fusion of caustic 

 baryta with pyrolusite and chlorate of potash affords a more 

 beautiful and homogeneous product than that by ignition of 

 nitrate of baryta with sesqui-oxide or bin-oxide of manganese ; 

 and also that the color by the latter is by no means as per- 

 manent, on account of the reducing action, in time, of traces 

 of nitrous acid remaining. He found, however, a better 

 method, in the addition of chloride of barium to a green boil- 

 ing solution of manganate of potash, by which a heavy, gran- 

 ular, though not crystalline precipitate is formed of a violet 

 almost blue color, which can be tolerably well washed by de- 

 cantation, and finally be easily drained on a filter. This loses 

 color, on drying, by gradually increasing the temperature, 

 until, at the lowest red-heat, it appears nearly white, with a 

 trace of grayish-blue. By heating it higher, with access of 

 air, or in an oxidizing flame, it gradually becomes perfectly 

 green, and by heating still further passes to a beautiful green- 

 blue, until finally, at a high temperature, it forms a dirty, 

 grayish -brown mass by reduction of the manganic acid. 

 With a solution of permanganate of potash, chloride of ba- 

 rium affords, after continued boiling, a peach-blossom colored 

 precipitate, while the liquid retains an intense violet color. 

 This precipitate of permanganate of baryta can be washed 

 by decantation, and dried at 212, without changing color. 

 With a gradual elevation of the temperature, however, it 

 loses color, but, unlike the manganate, does not afford either 

 a blue or green compound by simply heating with access of 

 air; on the contrary, it rapidly passes into the grayish-brown 

 compound before mentioned ; so that the permanganate, un- 

 der these conditions, is not adapted to the preparation of ba- 

 ryta green. While the pigment produced by ignition of the 

 manganate surpasses in beauty that produced by the other 

 two methods, and although it might be possible to improve 

 that produced from the nitrate of baryta by manufacturing it 

 in a reverberatory furnace under a strong oxidizing flame, in 

 no case is the green equal in beauty to the blue-green al- 

 most azure-blue compound, of which no public notice has 

 been taken. This pigment has different shades, according to 



