CRUDE MINERAL PIGMENTS. 



BY JOSEPH STRUTHERS. 



[Joseph Struthors, mineralogist; horn iit New York eity in lS(i5, and attenrled 

 the School of Mines, Columbia college (now Columbia university), RraduatinR in 

 the course of chemistry in ISSo; for fifteen years after his graduation he was on the 

 staff of instructors of the department of metallurgy at Columbia university; organ- 

 ized and conducted the first summer school in practical metallurgy of Columbia 

 university (lSi)6), which was at Butt(% Mont. Dr. Struthers has visited many 

 metallurgical plants in the United States and Europe, and he has carried on spetual 

 metallurgical investigations; he has written numerous articles for th(^ Engineering 

 and Mining Journal, Mineral Resources of the Unit(>d Stat(!S, Twelfth Census of the 

 United States and School of Mines Quarterly, and is assistant editor of the Transac- 

 tions of the American Institute of Mining Engineers; appointed Field Assistant to 

 the United States Geological Survey for 1901 and 1902, and in May, 1903, special 

 agent for the United States census.] 



Pigments are substances, both natural and artificial, 

 which are usually insoluble in water, oils, and other neu- 

 tral solvents, and are used to impart color to a body either 

 by surface adhesion or by direct admixture with its sub- 

 stance. Generally there is no chemical combination be- 

 tween the pigment and the body it covers. When mixed 

 with a drying oil, or with water containing oil or size, the 

 pigments form the basis of paint which is used for decora- 

 tive or protective purposes. 



The natural pigments, the only ones with which this re- 

 port is concerned, are among the most important but are 

 fewer in number than those prepared artificially by chem- 

 ical precipitation or other processes. According to Thorp 

 the chief pigments are classified as follows: 



Whites: White lead, lead sulphate, leadoxy chloride, zinc 

 white, zinc sulphide, barytes, gypsum, and whiting. Blues: 

 Ultramarine, Prussian blues, smalt, cobalt blues, copper 

 blues, and indigo. Violet: Ultramarine. Greens: Ultra- 

 marine, Brunswick green, chrome green, Guignet's green, 

 copper greens, and copper and arsenic greens. Yellows: 

 Chrome yellow, yellow ocher, cadmium yellow, orpiment, 

 litharge, gamboge, and Indian yellow. Orange: Orange 

 mineral, chrome orange, and antimony orange. Reds: Red 

 lead, chrome red, red ocher, Venetian red, vermilion, realgar, 

 antimony red, and carmine. Browns: Umbers, Vandyke 



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