48 HOW CEOPS GEOW. 



TABLE OF ATOMIC "WEIGHTS AJTB SYMBOLS OE ELEMENTS.* 



Element. 



Hydrogen 



Carbon 



Oxygen 



Nitrogen 



Sulphur 



Phosphorus 



Chlorine 



Mercury 



Potassium 



Sodium 



Calcium 



Iron 



Multiple ProportionSi — When two or more bodies unite 

 in several proportions, their quantities, when not expressed 

 by the atomic weights, are twice, thrice, four, or more times, 

 these weights ; they are multiples of the atomic weights by 

 some simple number. Thus, carbon and oxygen form two 

 commonly occurring compounds, viz., carbonic oxide, con- 

 sisting of one atom of 'each ingredient, and carbonic acid, 

 which contains to one atom, or 12 parts by weight, of car- 

 bon, two atoms, or 32 parts by weight, of oxygen. 



Molecular Weights of Compounds. — ^While elements 

 unite by indivisible atoms, to form compounds, the 

 compounds themselves combine with each other, or 

 exist as molecules,^ or aggregations of atoms. It has 

 indeed been customary to speak of atoms of a com- 

 pound body, but this is an absurdity, for the smallest par- 

 ticles of compounds admit of separation into their elements. 

 The term molecule implies capacity for division just as 

 atom excludes that idea. 



* Latterly, chemists are mostly inclined to receive as the true atomic weights 

 dmiUe the numhers that have heen commonly employed, hydrogen, chlorine, 

 and a few others excepted. 



t Latin diminutive, signifying a litUe mass. 



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