318 Dr. T. Sterry Hunt on 



from the observations on the secular wires referred to in the 

 opening paragraph of this paper. I hope, therefore, that though 

 these experiments are far from complete, even this preliminary 

 account of them may not be without interest to the Mathe- 

 matical and Physical Section of the British Association. 



XLII. Integral Weights in Chemistry. 

 By T. Sterry Hunt, LL.D., F.R.S* 



1. "TN approaching the discussion of integral weights in 

 -1- Chemistry, it is important to consider in the first place 

 what we have elsewhere noticed as the distinction between 

 dynamical and chemical phenomena. The passing alterations 

 in the volume of any species resulting from variations of tem- 

 perature are dynamical ; but beyond certain limits these pro- 

 duce more or less permanent changes of state, which are 

 chemical changes. Such are the condensation of gases or 

 vapours to liquids and solids, the vaporization of these, the 

 fusion of solids, and also the transformations alike of gaseous, 

 liquid, and solid species, whether elemental or complex, which 

 are comprehended under the general head of chemical meta- 

 morphosis. These changes, as is well known, are influenced 

 by pressure, which favours or retards them, as the case may 

 be. The phenomenon of elasticity in gases and vapours is 

 apparently a manifestation of chemical change or metamor- 

 phosis, giving rise to new and unstaple species. 



2. All changes of state in matter may, as we have elsewhere 

 shown, be included under the two heads of (1) metamorphosis, 

 wdiich includes homogeneous integration and disintegration, 

 and (2) metagenesis, which includes heterogeneous integra- 

 tion and disintegration. All such changes are subordinated 

 to simple relations of measure, of number, and of weight, as 

 is apparent in definite and multiple proportions, and in pro- 

 gressive series. These relations are best exemplified in the 

 case of gases and vapours, w r here the weight at 0° temperature 

 and 760 millim. pressure of a given volume of the lightest 

 known species, namely hydrogen gas, is made the unit. The 

 weight of a like volume of any other gas or vapour reduced 

 to the same standard temperature and pressure, and compared 

 with this unit, is sometimes designated its equivalent weight. 

 Inasmuch, however, as in chemical union or integration of 

 gases and vapours the most frequent cases are in the propor- 

 tion of one to one or one to two volumes, the condensation in 



* Communicated by the Author, having been read before the Meeting 

 of the British Association for the Advancement of Science at Manchester, 

 September 1, 1887. 



