PAINTS, DYES, AND VARNISHES 



SOME "CHROME" PIGMENTS 



For making the yellow pigments or more specif- 

 ically, the chrome-yellow pigments the compounds of 

 the same three important metals, lead, barium, and zinc, 

 are also the most important. Here again the product 

 of the lead salts is the one most sought by the practical 

 painter, although it is a very poisonous pigment, and, 

 as the chemist points out, lacks the permanency of the 

 other two. It has one cardinal point in its favor, con- 

 ceded by both chemist and artisan : it is a more brilliant 

 and beautiful yellow at first than any of the com- 

 pounds of the other metals. But this brilliant color is not 

 permanent, and when exposed for a long time changes 

 to a dull color much inferior to the yellows of either zinc 

 or barium. Nevertheless lead chrome yellow is the 

 most popular of the yellow pigments to-day for general 

 commercial purposes. 



Nature furnishes a lead chromate in the rare mineral, 

 crocoisite, found in some lead mines; but the chrome 

 yellow used for pigment-making is an artificial product. 

 It is made by mixing a solution of potassium chromate, 

 or bichromate, with a solution of some lead salt, fre- 

 quently the acetate of lead. Curiously enough, the 

 exact shade of color of the product depends to a very 

 considerable degree upon the relative amounts and 

 strengths of the two solutions used. In the ordinary 

 chemical reaction the molecules of the resulting com- 

 pounds will be the same, whatever the relative propor- 

 tions of the basic solutions; but in the production of 



