‘or the formation of the compound. Two conditions are in general 
sary for the formation of a compound. First, a degree of chemica 
or affinity sufficient for the combination, and secondly, the necessary 
ergy. A single cause is insufficient. The author here distingul 
e 
eb 
two ways. Certain bodies, H and O, H and Cl, CO and O, &e,, comb 
suddenly in unlinited quantities by means of a single spark, 
evolution of heat. Others, like N and QO, combine only gradually; 
heat is evolved, and the combination ceases with the cessation of the spa 
The formation of ozone is also a case in point. In the first case’ 
, h ap 
Then the spark furnishes the requisite energy, and each spark yields 
and O, but not upon N and O. In conclusion, the author takes 
against the assumption often made that the heat of combination |! 
tion of 23783 units. In each ease, besides the re 
site affinity must be present. Thus, in a simple mixture of | 
combination takes place until the affinities are sufficiently Inet 
the sary energy is always present. A further 2 
¢ heat of combination as the measure Of 4 
hat in certain combinations heat is absor! 
ical affinity would be negative.—Pog?- 
