PAINTS, DYES, AND VARNISHES 



called litharge, and in its amorphous form, massicot. 

 The crystalline salt is a dull yellow, while the amor- 

 phous one is a reddish yellow. These substances are 

 not used very generally as pigments, although there is 

 another lead oxide, in which the molecule contains lead 

 and oxygen in the proportion of three to four (Pb 3 O 4 ), 

 which is the bright-red pigment used by plumbers as a 

 cement for pipes. 



A yellow which is distinctly inferior in quality to the 

 chromic-acid salts of lead, zinc, or barium, is calcium 

 chrome yellow. It is a very permanent color, however, 

 and is much cheaper than the other three, so that it is 

 popular in places where price and permanency, rather 

 than beauty, are the principal conditions. 



"Turner's yellow," which was invented by James 

 Turner late in the eighteenth century, and was popular 

 for many years, is a pigment that has been superseded in 

 later years by the chrome and ochre pigments which will 

 be presently described. It was an oxychloride of lead, 

 made from litharge and ammonium chloride, and was 

 known under the various names, Montpelier yellow, 

 Cassel yellow, Kassler yellow, Verona yellow, and 

 probably others. 



"Naples yellow," a compound of the oxides of an- 

 timony and lead, which was a popular pigment at one 

 time, has also been replaced by the chromes, over which 

 it has no advantage. 



A beautiful and permanent chrome yellow is made 

 from the metal cadmium, but this pigment is too ex- 

 pensive for ordinary commercial purposes. It is some- 

 times used as an artist's pigment, but more generally 



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