Biology / by Dr. Charles Letourneau ; translated by William Maccall.

  • Charles Letourneau
Date:
1878
Catalogue details

Licence: Public Domain Mark

Credit: Biology / by Dr. Charles Letourneau ; translated by William Maccall. Source: Wellcome Collection.

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    cannot fix each more than one atom of chlorine or of bromine ; they are monoatomic, as, for instance, hydrogen. Calcium, barium, strontium, in order that their attractive power may be saturated, need to fix two atoms of chlorine ; they are diatomic, as, for instance, oxygen. Phosphorus, which in the perchlorure of phosphorus succeeds in fixing five atoms of chlorine, is pentatomic. It is these inequalities in the mode and the power of combina- tion, in the capacity of saturation, which we call the atomicity of each atomical species, designating specially by that expression the maximum capacity of saturation. However, hereby is by no means implied that a pentatomic species, for instance azote, can- not combine with less than five atoms. Azote, which fixes five atoms in the chlorohydrate of ammonia (AzH4Cl), is not more than triatomic in ammoniac gas (AzH3), and is only diatomic in the bioxide of azote. For the sake of greater clearness, the denomination atomicity is reserved to designate the capacity of absolute saturation. The capacities of inferior saturations aie called quantivalences. Thus then azote is pentatomic, but it is trivalent in gas ammoniac, and so on. This notion of atomicity has thrown a great light on the ultimate texture of bodies, and also on the march hither and thither of atoms in various combinations. In effect, free or combined, every atom tends to saturate itself by the annexion of other atoms. If, for instance, a tetratomic atom has combined with two atoms only, it ceases not to tend to saturate its attrac- tive force; it strives to fix two atoms more. But these two atoms once found, no other simple body can combine with our tetratomic atom, unless by displacing one or two of its atoms and becoming their substitute. If, for instance, we take from a carburet of saturated hydrogen an atom of hydrogen, the molecule thus mutilated can unite itself to an atom of chlorine. But the chlorine is monoatomic ; this, however, does not hinder it from fixing the complex molecule of the carburet, impoverished to the extent of an atom of hydrogen. The reason is that certain atomic groups, certain molecules, can play in combina- tions the part of a single atom. They are what we call com-
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