ULTRAMARINE. 113 



after cooling, and extract it with water. It yields 9 J pts 

 oxide of chrome. (Dingler's Journ. civ. 158.) 



5. Some other pigments are prepared, partly by heat, as 

 sulphuret of arsenic and ultramarine, and partly from solution, 

 as sulphurets of cadmium and of antimony. Of these, wo 

 shall only notice the ultramarine, which, having been a valued 

 pigment found in the mineral kingdom, was analyzed, and its 

 composition imitated successfully. It is now made on a large 

 scale, and of very different qualities in regard to color or 

 durability. 



Ultramarine, Artifieial. — Recipes for the preparation of 

 this beautiful blue color have been given by C. Brunner (Pogg. 

 Annal. Ixviii. 541-561) ; by Priickner (Journ. f. Prac. Chem. 

 xxxiii. 257) ; Dr.Winterfield, in Polytech. Archiv. Mendelsohn, 

 6th year, 99, 260, 265, Berlin, 1842. 



Brunner does not think that iron is necessary to produce 

 the blue color, while Priickner and Winterfeld hold that iron 

 is essential to the beauty of the color. Dr. Eisner, in a neat 

 essay (Jour. f. Prac. Chem. xxiv. 385, &c.), showed that the 

 color was due to a small content of sulphuret of sodium with 

 sulphuret of iron, and that neither of these alone could pro- 

 duce it. Rolle, under Dr. E.'s direction, repeated many ex- 

 periments, which strengthened his former conclusion that 

 sulphuret of sodium and iron, though in minute quantity, are 

 absolutely necessary to produce the color. Brunner states 

 that the finest color is obtained by putting a thin layer of 

 flowers of sulphur over a layer of the unfinished blue, and 

 heating gently to volatilize the sulphur, but at the lowest heat 

 required to burn it off. This is repeated 3 or 4 times. It 

 increases 10-20 per cent, in weight. Eisner tried the effect 

 of burning off sulphur repeatedly, but although the color was 

 darkened, it did not improve its tone. Others tried it, with 

 no more success. 



3. Fine ChexMicals and Pharmaceutics. 

 A large number of fine preparations are made, on a larger 

 or smaller scale, for the use of the chemist and the physician, 



