CHEMISTRY. 65 



phylle. The coloring principle of logwood is hcematoxyline : 

 carmine is a beautiful pink color derived from the cochineal 

 insect: several substances produce yellow and brown. 



Nearly all vegetable colors are destroyed by the action of 

 solar light, and all of them, without exception, by the action 

 of chlorine gas : acids and alkalies destroy or change them. 

 No coloring principle has yet been found in plants, capable of 

 being transferred to other bodies so as to produce a green: 

 greens are therefore produced by the action of blues upon a 

 base of yellow. Substantive colors are those which combine 

 directly with the fibres of cloth without the intervention of a 

 mordant : adjective colors require the assistance of a mordant 

 to make them permanent, 



INORGANIC ELEMENTS OF PLANTS. 



Besides the organic elements which enter into the compo- 

 sition of plants, and which, as before stated, are themselves in 

 most cases composed of the four principal elements, carbon, 

 oxygen, hydrogen and nitrogen, there are several inorganic 

 substances, which are constantly present in all plants, and in 

 about the same relative proportions in the same plant in all 

 cases. These are in combination with the gases and with one 

 another. Chlorine, iodine, sulphur, phosphorus, potassium, 

 sodium, calcium, magnesium, aluminum, silicon, iron and man- 

 ganese, 



CHLORINE. 



Chlorine is a yellowish green gas, having a pungent, suffo- 

 cating odor ; it is soluble in water, extinguishes a lighted taper, 

 has a specific gravity of 2.47, and when submitted to the 

 pressure of four atmospheres, is condensed into a limpid, 

 yellow liquid. This gas is a supporter of combustion, but not 

 of animal life : a piece of phosphorus, gold leaf, potassium or 

 sodium, introduced into it, inflame and burn spontaneously. 

 Chlorine has but little affinity for oxygen, its chemical pre- 



e* 



