ments; and, secondly, at the moment certain ele 

 ments are liberated from their combination, they are 

 very specially active in combining with other, dif- 

 ferent elements; that is to say, the changes are not 

 equal that the liberated elements will either retain 

 their elementary condition or combine to form com- 

 pounds, but the cases, in which compounds are 

 formed are in great majority. 



CHEMICAL NOTATION, (From ?wto, I mark) - 

 Is the art or practice of recording chemical facts by 

 short marks, letters, numbers, or other signs. Al- 

 ready the first capital letter or the first and one 

 of the small letters of the Latin names of the 

 elements have been employed as contractions, 

 or short-hand expressions, or symbols of the whole 

 name. Thus H has been used for the word "hydro- 

 gen," and Cl for ''chlorine. " A second function of such 

 a symbol is that of indicating one atom. Thus H 

 stands not only for word or substance "hydrogen," 

 but for one atom of hydrogen. Large and small 

 figures (2 or 2 ) indicate a corresponding number of 

 atoms, the small figure only multiplying the one 

 particular symbol to which it is attached, while a 

 larger figure- multiplies all the symbols it precedes. 

 Thus H 2 means two atoms of hydrogen, and C^ two 

 atoms of chlorine; while 2HC1 means two atoms of 

 hydrogen and two atoms of chlorine, or, in one 

 word, two molecules of hydrochloric acid. 



The position of symbols counts for 'something. 

 Thus HC1 indicates not only the substances hydro- 

 gen and chlorine, single atoms of each of the sub- 

 stances, but also that the two substances are joined 

 together by the chemical force. If the two letters were 

 placed one under the other, or at some distance 

 apart, or were separated by a comma or a plus 

 sign ( + ), they would be undertood to mean a mere 



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