SCIENCE IN THE INDUSTRIAL WORLD 



pigment of this group. It was supplanted as a pigment 

 soon after 1778, when the Swedish chemist, Scheele, 

 announced the discovery of the pigment that has since 

 borne his name. This is a basic arsenite of copper, and 

 although somewhat better as a pigment than the copper 

 greens known before its discovery, it cannot be con- 

 sidered as a high-class pigment, and dropped out of use 

 after the discovery of emerald green in 1814. This green 

 is an aceto-arsenite of copper, and is very poisonous. It 

 has good covering power, brilliant color, and in dry 

 places is very permanent; but on account of the dangers 

 attending its use it has fallen into disfavor as a pigment 

 except with artists. This waning in popularity of emer- 

 ald-green as a pigment for over half a century, has been 

 offset by a corresponding increase in popularity of this 

 substance as an insecticide. Thousands of bushels of 

 vegetables are saved annually by the use of Paris green. 



Of the other copper-green pigments, a basic carbonate 

 known as "mineral green," or "malachite," occurs as a 

 natural green mineral in several places on the earth. 

 Green verditer is also a basic carbonate of copper which 

 is made artificially, as is also Bremen green. But 

 none of these substances need be considered seriously 

 in the list of practical pigments in use to-day. 



Terre verte, or Verona green, as it is sometimes called, 

 is a natural green mineral pigment of very complex com- 

 position. It contains silica, ferrous oxide, potash, mag- 

 nesia, and possibly alumina, soda, and manganese. 

 It is very permanent as a pigment, and was used ex- 

 tensively by the ancient and medieval painters, who had 

 no other permanent green pigment. It is poor in body 



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