ENRICHING SOIL COMMERCIAL RESOURCES 103 



experiment, on different parts of which the 

 various elements and combinations of them 

 may be applied. 



SUGGESTIONS ON CHAPTER VI 



127o. An element is a simple substance. It is not made by a 

 combination of any other substances, and by no known means can 

 it be separated into any other substances. Sulfur, nitrogen, and 

 phosphorus are elements. The known elements number about 70. 



1276. The elements are represented by one or more letters, 

 called symbols. Usually the first letter of the name is employed. 

 Thus, nitrogen is designated by N, phosphorus by P, sulfur by 

 S. When the names of different elements begin with the same 

 letter, as sulfur and sodium, this rule cannot be followed. In 

 such cases, letters from the name of one of the elements in some 

 other language are used. Thus, Na is tised for sodium, natrium 

 being the Latin of sodium. Similarly, P might represent phos- 

 phorus or potassium ; hence K is used for potassium, which in 

 Latin is kalium. 



130. Compounds result from the chemical union (30c) of two 

 or more elements. The compound may not resemble in any way 

 any of the elements contained in it. The proportions in which 

 elements unite vary, and the same elements may be made to 

 unite in different proportions. The same compound always con- 

 tains the elements in exactly the same proportion. 



130fc. Compounds are represented by writing together the 

 symbols of the elements composing them, together with figures 

 to represent the proportions. Thus, potash, K 2 O, is a compound 

 of two parts of potassium and one of oxygen, O. Lime, CaO, is 

 composed of the elements calcium, Ca, and oxygen, and its 

 chemical name is calcium oxid. Other compounds are nitrate of 

 soda, NaNOa ; ammonia, NH 3 (H representing the element hy- 

 drogen); water, H 2 O ; sulfurie acid, HoSCu ; ammonium nitrate, 

 NH 4 NO 3 ; ammonium sulfate (NH 4 ) 2 SO4 (the NH 4 being taken 

 twice); starch, CH| O5 (C; representing carbon); salt, Na(.'l 

 (01 standing for chlorin). 



