52 AGRICULTURAL CHEMISTRY 



condition, may undergo spontaneous combustion. The 

 fermentation which takes place produces combustible 

 gases which, at suitable temperature, ignite; 

 the burning gases, in turn, ignite the carbon 

 of the material. Substances containing a 

 great deal of oil and materials of low kindling 

 temperature, as carbon bisulfid, phosphorus 

 and sulfur, under suitable conditions of tem- 

 perature and air, readily undergo spontaneous 



Fig. 24 Candle combustion, 

 flame. 3. Non- 

 luminous cone. i n C ase of fire, the laws governing combus- 



4. luminous 



line. 5,6. outer tion should be taken advantage of. If the 



non-luminou s 



envelope. fire is a small one, cut off the supply of air, 

 and the fire is extinguished. This can be accomplished 

 by the use of sand, wet blankets, or any material that 

 will cut off the supply of air. In order for spontaneous 

 combustion to take place, there must be (i) a combusti- 

 ble substance, which (2) is heated to a suitable tempera- 

 ture, and (3) in the presence of air. 



55. Carbon a Decolorizer and Deodorizer. Wood and 

 animal charcoal have the power of absorbing gases and 

 some coloring materials from solutions. In the manu- 

 facture of sugar, some of the impurities are removed by 

 bone-black or animal charcoal filters, and in purifying 

 water, charcoal filters are often used. The power of car- 

 bon to abstract gases and coloring-matter is largely a 

 physical property. In the soil, the carbon compounds de- 

 cay and produce humus, which has some of the physical 

 properties of charcoal to absorb gases and soluble bod- 

 ies. 



