FOUNDATION FACTS AND PRINCIPLES 3 



Chemical action. Chemical reaction is the union of two or more 

 elements into a compound, or the separation of a compound into 

 its elements, or the formation of new compounds from other com- 

 pounds. In the most common chemical reactions heat is evolved. 



Place some coal in the stove, raise the temperature to the kin- 

 dling point, and 32 pounds of the element oxygen entering the vent 

 of the stove in gas form will unite with 12 pounds of the element car- 

 bon in the coal and 44 pounds of the compound carbon dioxid (CO 2 ) 

 will form and pass off as a gas througn the chimney. After this 

 chemical reaction is completed, the stove is found to contain only 

 a few ounces of ashes, which represent the impurities in the coal. 



From this compound, carbon dioxid (CO 2 ) , which is always pres- 

 ent in the air in small amount, all agricultural plants obtain their 

 supply of carbon and oxygen, which together constitute about 

 90 per cent of the total dry matter contained in plants. 



Combining weights. Combining weights of elements are the 

 relative proportions in which those elements combine to form 

 compounds. The combining weight of the element hydrogen is 

 smaller than that of any other element, and for this reason all other 

 combining weights are referred to that of hydrogen as the stand- 

 ard, or unit, of weight. The combining weight of hydrogen is i. 

 One part of hydrogen will unite with 35.5 parts of chlorin to form 

 the compound hydrogen chlorid (HC1), which is also properly 

 called hydrochloric acid, and sometimes incorrectly called " mu- 

 riatic " acid. Thus, the combining weight of chlorin is 35.5. 



We may take i pound of hydrogen and let it unite with 35.5 

 pounds of chlorin to form 36.5 pounds of the compound HC1; 

 or we may use i ounce of hydrogen and 35.5 ounces of chlorin, 

 or i gram of hydrogen and 35.5 grams of chlorin, or i milligram of 

 hydrogen and 35.5 milligrams of chlorin. All that is necessary is, 

 that we maintain these proportions. This is one of the absolute 

 mathematical laws of chemistry and is fundamental to the prin- 

 ciples of soil fertility and plant growth. If we try to combine 3 

 parts of hydrogen with 35.5 parts of chlorin, 36.5 parts of the com- 

 pound HC1 would be formed and 2 parts of hydrogen would be 

 left in its original form. 



Atoms. An atom is the smallest particle of an element. It is 

 not known how small the atom is, but it is known that the weight of 



