SCIENCE IN THE INDUSTRIAL WORLD 



By using white lead, potassium bichromate, and 

 caustic soda in certain proportions and boiling for a 

 short time, a red of considerable brilliance is formed, 

 which is known commercially under various names, 

 such as Persian red, Victoria red, American vermilion, 

 Chinese red, Derby red, chrome red, and several less 

 familiar names. 



The chrome-lead pigments are, almost without ex- 

 ception, very good pigments from the practical painter's 

 standpoint. They have good covering powers, bril- 

 liancy, and permanency under ordinary conditions. 

 They have the defects of all the other lead pigments, 

 but their good qualities are so pronounced that, for 

 yellow paints, they may be said to have scarcely any 

 competing rivals for first place commercially. 



The zinc chromes, while distinctly inferior to the 

 lead chromes as pigments, are, nevertheless, important. 

 The method of making them does not differ essentially 

 from that of making the lead chromes, except that a 

 zinc salt is used in place of a salt of lead. This salt is 

 mixed in definite proportions, either with chromic acid, 

 or with bichromate of soda, or potassium. The tints 

 obtained from these mixtures are known severally 

 in commerce as "marigold tint," "lemon tint," "pale 

 tint," "zinc chrome," "deep chrome," etc. Most of 

 these pigments have good color and body, and mix 

 readily with other pigments. 



Ranking next in importance to the chromes as yellow 

 pigments, although usually considered distinctly in- 

 ferior to them, are the natural mineral pigments, ochres 

 and siennas. These substances are widely and abun- 



