22 PRACTICAL FARM CHEMISTRY. 



the use of vegetation. The precious but volatile 

 ammonia is not only held, but brought in immediate 

 contact with oxygen, all condensed in the charcoal 

 pores, and changed into the stable nitric acid, etc. 

 This power of absorbing and condensing gases gives 

 charcoal, also, its great value as a disinfectant and 

 deodorizer. 



New soils generally have an abundance of carbo- 

 naceous matter— the decomposed remains of veget- 

 able productions, leaf mould, humus, peat, veget- 

 able mould — as this always accumulates in forests, 

 pastures and swamps. Various acids, such as 

 ulmic, humic, etc., contained in these substances, 

 are merely carbonic acid yet in process of prepara- 

 tion, or unfinished. Carbon of the vegetable matter 

 combines with a little oxygen and forms ulmic acid; 

 this combines with a little more oxygen and- forms 

 humic acid; this again combines with more oxygen, 

 and forms geic acid, and so on through several more 

 steps until the final result, carbonic acid is reached. 

 All these combinations of carbon with oxygen, 

 under certain conditions, can serve as food for 

 plants, while the constant absorption of oxgen also 

 favors the production of nitrogen compounds. 



By constant cropping, without application of 



bulky manures, the carbonaceous matter in the soil 



becomes exhausted. The process of oxidation, or 



decay, stops, since there is no material to work on. 



The production of carbonic acid 



^*in^the^^u.*^ ceases, and with it the supply of a 

 most important plant food to the 

 roots. The soil water loses part of its solvent power. 

 The conversion of nitrogenous matter into ammonia 

 and nitric acid (in which forms alone nitrogen can 

 be taken up by plants) also comes to an end. In 



