COLORING MATTERS. 121 



etable colors, are green, yelloWj blue and red. But all the colors 

 of (lyed-stuffs, are produced from blue, red, yellow and black, 

 though the latter does not exist in the vegetable kingdom, but 

 is formed by adding mineral bodies to the acid of gall-nuts or 

 logwood. 



Btue dyes are derived from the indigo plant [indigofera), a 

 genus of plants of which there are sixty species. They are 

 found in India, Africa and America. Litmus has a blue color, 

 and is used as a chemical re-agent. 



Red dyes are derived from the cochineal, an insect which feeds 

 on one species of the cactus ; from lac, archil, madder. Brazil- 

 wood and logwood. 



Lac is a resinous substance, derived from the /cms Indica and 

 religiosa, and is commonly known as shell-lac. Archil, is obtain- 

 ed from a species of lichen {parmtlia roccdla), the best quality 

 of which is found in the Canary Islands. 



Madder is the root of the ruhia tinctorum, a plant cultivated in 

 countries bordering on the Mediterranean Sea. This plant is 

 also used for a great variety of colors, forming by the addition 

 of mineral substances, madder-yellow, madder-orange and mad- 

 der-brown . 



Brazil-wood is found in Brazil, and is obtained from several 

 species of the ccEsalpina (sapan, crista, etc.). The red coloring 

 matter of this wood, is rendered yellow by acids, and violet by 

 alkalies. 



Logwood is the wood of the Haematoxylon Campeachianum 

 found in Jamaica, and the eastern shores of Campeachy. This 

 wood is chiefly employed by the calico printer, to give cotton 

 a brown or black color. 



Yelloio dyes are obtained from the quercitron bark, which is 

 taken from [quercus nigra), a large tree growing in this country ; 

 from tumeric [curcuma longa), saffron [crocus sativus), and from 

 fustic [morus tinctoria), a large tree which grows in Brazil ; 

 from iveld, which is the dried leaves of reseda luteola, a Eu- 

 ropean plant ; from Persian berries [rhamnus infectorius) ; from 

 sumac [rhus coriaria), which grows spontaneously in Italy and 

 the south of France. 



2. Fixed oils are usually obtained from seeds, as the almond, 

 linseed and poppy-seed. Olive-oil is extracted from the pulp 

 around the stone. After being boiled, these oils dry more 

 rapidly, and are then used in forming paints ; when mixed 

 with lampblack, they constitute Printer's Ink. In drying ra- 

 pidly, these oils absorb so much oxygen, as to take fire spon- 



