116 



CARBON AND ITS COMPOUNDS 



ting a tube of kerosene into a vessel of water, and gradually heating the 

 water. At the same time we force air bubbles through the kerosene, 

 with the result that a froth rises to the mouth of 

 t=- the tube. When the froth can be lighted with 

 a match, the temperature shown by the ther- 

 mometer is the flashing point of the kerosene. 

 In most states the flashing point is 150 F., or 

 65 C. 



Air and 



Kerosen 



Vapor 



FIG. 99. 



123. Other Compounds of Carbon. 



Carbon, hydrogen, and oxygen form a 

 large number of compounds. Among 

 them are the fats and sugars, starch, cellulose (the 

 material of wood, cotton, and paper), acetic acid (the 

 acid of vinegar), lactic acid (the acid of sour milk), 

 ordinary alcohol, wood alcohol, ether, etc. 



Carbon, hydrogen, and nitrogen form aniline, and the 

 poisonous prussic acid ; while carbon, hydrogen, nitrogen, 

 and oxygen make up the principal part of all living tissue. 

 These compounds of carbon are studied in Organic Chem- 

 istry. 



124. Dry Distillation of Coal and Wood. By "dry 

 distillation " we mean the heating of solids, and the col- 

 lecting of the materials that distill off. It is not a physical 

 change, like the distillation of water 

 (cf. 83) ; because the solids we ' ' dry 

 distill" are decomposed in the pro- 

 cess. When coal is " distilled, " gases, 

 liquids, and solids are given off, and 

 coke and ' ' gas carbon " remain behind 

 (cf. 119). The gases are known as illuminating gas; 

 they are chiefly hydrocarbons and hydrogen. Soft coal 



FIG. 100. 

 Dry Distillation of Wood. 



