ELISHA MITCHELL SCIENTIFIC SOCIETY Ae 
ity between them. The number of chlorine atoms with which 
it will unite depends upon the possibility of harmonizing the 
respective motions, As the temperature may affect these 
motions and also impart a more rapid molecular motion, it is 
evident that the harmony, or equilibrium, will depend upon 
the temperature and that a temperature may be reached at 
which no harmony is possible and hence no compound can be 
formed. ‘The phosphorus atom mentioned can, as we know, 
form a stable molecule with five atoms of chlorine, On in- 
creasing the temperature this becomes unstable and only three 
atoms can be retained. Neither with four atoms nor with 
two is there harmony of motion. A sufficiently high temper- 
ature may prevent any harmony of motion whatever being at- 
tained and hence union may become impossible. 
As to other influences than those of temperature, we can 
see that the equilibrium between the atom of phosphorus and 
the five atoms af chlorine may be upset by such a molecule 
coming within the influence, electrical or vibratory, of a mol- 
ecule of water. The atoms must rearrange themselves for a 
new state of equilibrium and so an atom of oxygen takes the 
place of two atoms of chlorine, giving again a condition of 
harmony. In other cases the motion of the molecule of water 
may be of such a character as to directly harmonize with that 
of the original molecule and so to enter into equilibrium with 
it, a definite number of such molecules of water affording a 
condition of maximum stability. This we call water of crys- 
tallization. Such:'molecules would be more or less easily sep- 
arated by an increase of temperature and where several mole- 
cules of water were attached the highest temperature would 
be necessary for freeing the original molecule from the last 
water molecule. | 
A carbon atom finds its most perfect state of equilibrium 
where four atoms of hydrogen or their equivalent move in har- 
mony with it. But there is a second state of equilibrium 
where only half that number of atoms are moving with it. 
This state does not seem to be a possibility where there are 
hydrogen atoms but is readily possible where the equivalent 
number of oxygen atoms is concerned. Such a molecule, how- 
