SCIENCE IN THE INDUSTRIAL WORLD 



fugitive, however, and is only useful where a tempo- 

 rarily brilliant effect is desired. A very pale, although 

 permanent, red is prepared from magnesia and nitrate 

 of cobalt, but this pigment is not in general use. 



GREEN MINERAL PIGMENTS 



Of the green mineral pigments probably the most im- 

 portant for ordinary painting are the various shades of 

 Brunswick green. Emerald green, the poisonous 

 substance known as "Paris green" in America, which 

 was once very popular as a pigment, and is still used 

 by artists for their purposes, has now been replaced 

 largely by a coal-tar product which will be referred to a 

 little later. The true chrome green and other copper 

 greens are also of considerable importance as pigments, 

 and there are several others. 



The so-called Brunswick greens formerly in use were 

 compounds of copper; but these have now been com- 

 pletely supplanted by the more modern greens of the 

 same name but of different compositions. The modern 

 Brunswick greens, which are known commercially as 

 "pale," "middle," "deep," "extra-deep," etc., are 

 mixtures of barytes, Prussian blue, and chrome yellow, 

 or compounds of similar chemicals in varying propor- 

 tions. The relative amount of Prussian blue determines 

 the shade of the green pigment, the larger the amount 

 the deeper the shade. Thus one hundred parts of 

 barytes, two parts of Prussian blue, and thirty-five 

 parts of chrome yellow make a pale Brunswick green; 

 whereas if the amount of Prussian blue is increased to 



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