242 



METALS. 



Obs. Occurs usually in serpentine rocks, in imbedded 

 masses or veins. Some of the foreign localities are the 

 Gulsen mountains in Styria ; the Shetland Islands ; the de- 

 partment of Var in France ; Silesia, Bohemia, etc. 



In the United States, it is abundant in Maryland in the 

 Bare Hills near Baltimore, and also in Montgomery county 

 at Cooptown in Harford county, and in the north part ol 

 Cecil county ; occurs also in Townsend and Westfield, Ver 

 mont, and at Chester and Blan.dford, Mass. It is also foun 

 at Hoboken, N. Y., and at Milford and West Haven, Conn, 

 in Pennsylvania in Little Britain, Lancaster county, anc 

 West Branford, Chester county, and on the Wisahicon, 11 

 miles from Philadelphia. 



Uses. The compounds of chrome are extensively used 

 as pigments. These compounds are obtained either from 

 chromic iron or the native chromate of lead, (see under 

 lead.) The chromate of lead and copper (vauquelinite) is 

 too rare to be employed for this purpose. The chromate of 

 potash is readily formed by mixing equal parts of nitre and 

 the powdered chromic iron and exposing the mixture in a 

 crucible to a strong heat for some hours. The soluble part 

 is then washed out, and the process is repeated with the in- 

 soluble portion (digesting it first in muriatic acid to remove 

 the free oxyd of iron and alumina) till all the ore is decom- 

 posed. The colored liquid obtained from the washings is 

 carefully saturated with nitric acid, and concentrated by 

 evaporation till crystals of nitre cease to be deposited. Being 

 then set aside for a week or two, it gradually deposits abun- 

 dant crystals of the yellow chromate of potash. Chromate 

 of lead, called also chrome yellow, is the most common chrome 

 paint used. It is made by adding to the liquid obtained as 

 above stated, before its crystallization, a solution of acetate 

 of lead (sugar of lead) till it is saturated. The yellow pre- 

 cipitate washed out and dried, is the chrome yellow of com- 

 merce. It is used as a yellow pigment both in oil and water 

 colors, calico printing, dyeing, and porcelain painting. This 

 material is largely manufactured at Baltimore, Md. The 

 native nitrate of soda of Peru, has been suggested as a sub- 

 stitute for nitre in the above process. 



Another mode of this manufacture recently proposed, con- 



Where does chromic iron occur ? What are its uses ? How is iho 

 ore treated ? What is chrome yellow, and how is it made 1 





