relative weights of atoms, for we cannot know the 

 absolute weights. All that is known is that the 

 chlorine atom, for instance, is 35.5 times as heavy as 

 the hydrogen atom, whatever the absolute weight of 

 the latter may be, and the iodine atom 127 times as 

 heavy. The quantity of metal which with 35.5 of 

 chlorine will form a chloride, will require 127 of 

 iodine to form an iodide. 



QUANTIVALENCE OF ATOMS. Turning from the 

 weights of atoms, their value may now be con- 

 sidered; quantivalence may be stated. The chem- 

 ical value of atoms in relation to each other, 

 may be compared to the exchangeable value of 

 coins. As compared with a dime, the twenty 

 cent piece would be two valued and the fifty 

 cent piece five valued. Here again, hydrogen is 

 conveniently adopted as the standard of com- 

 parison. Chlorine, iodine, and bromine, as well as 

 potassium, sodium, and silver among the metals, 

 are, like hydrogen, univalent (u-niv'-a-lent, from 

 unus, one, and valens). An atom of oxygen in its 

 relations to an atom of hydrogen is bivalent (pro- 

 nounced thus, biv'-a-lent, of double worth, from 

 bis, twice, and vale?is}\ an atom of it will displace 

 two atoms of hydrogen, or combine with the same 

 number; nitrogen is usually trivalent (triv'-a-lent; 

 from tres, three, and vale/is}', and carbon, quad- 

 riv-a-lent (from quatuor, four, or quater, four times, 

 and valens}. Phosphorus, arsenicum, antimony, and 

 bismuth, like nitrogen, usually exhibit trivalent 

 properties; but the composition of certain com- 

 pounds of these five elements shows that the several 

 atoms are sometimes quinquivalent (quin-quiv-a- 

 lent; quinquies, five times). Sulphur, chromium, 

 manganese, iron, cobalt, and nickel are sexivalent 

 (sex-iv-a-lent, from sex, six, or sexies, six times, and 



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