110 COPPER. 



of copper is formed, which is of a green colour, and 

 of an astringent taste. A solution of it is used as 

 a sympathetic ink ; for letters written with it will 

 become yellow by warming, and will disappear 

 again when cool. 



The acetous acid in a sufficient degree of con- 

 centration dissolves copper, but when not concen- 

 trated, as in vinegar, it acts upon it very slowly, and 

 forms common verdigris, which is an impure 

 acetate of copper. This being dissolved in distilled 

 vinegar, and subjected to evaporation, crystals are 

 produced which constitute what is called distilled 

 verdigris. 



Copper is employed in making kitchen utensils ; 

 but as these vessels are liable to be corroded by 

 the acids and fatty substances used in culinary 

 preparations, they often become dangerous, as all 

 the salts of copper are poisonous. Culinary utensils 

 of copper should always be well tinned, but those 

 of iron tinned are safer, as iron has no poisonous 

 quality. The alloys of copper with other metals 

 are very useful. 



Tombac is formed of copper, arsenic, and tin. 



Prince's metal, or Pinchbeck, is made of copper 

 and zinc. 



Brass is also formed of another proportion of 

 copper and zinc. 



Bronze is made of copper and tin. 



Bell-metal is also of copper and tin, but with 

 more tin than the latter alloy. 



A solder for silver is made of copper and 

 silver. 



