90 ©. Marignac—Chemical Equivalents and Atomic Weights. 
an Italian philosopher, Avogadro, on the equality of the mole- 
cules of all bodies in a gaseous state. This principle is hal 
placed in opposition to the law of Gay Lussac, on the simple 
relations which exist between volumes of gases, capable oe com- 
bining with one another, which law was established a few years 
before, and which, to tell the truth, is not in contradiction with 
the hypothesis of deenireaie From this question arose another, 
on the relative merits = the chemical notations, expressed in 
equivalents or in atom 
For the present, I will not discuss the first of these 5 vie 
The truth of the principle of Avogadro can only be admitted 
on the condition of supposing that the atoms of Peaplé gases 
cannot exist in a free state, but are welded together in_ pairs, 
forming molecules occupying two volumes, like the molecules 
and for phosphorus and arsenic, whose molecules must contain 
four atoms. 
This hypothesis is not absurd in itself. It may account for 
certain chemical rine such, for instance, as the greater energy 
of action that bodies possess in a nascent state, or before their 
atoms have coed biel two by two to form molecules; also for 
the ease with which certain reactions take place, as pointed o out 
by M. Wiirtz. It also explains several physical facts, such as 
the equality of specific heat for the same volume of simple or 
compound gases, whose molecule is formed of two atoms, as 
carbonic oxide, hydrochloric acid. It found lately an important 
poe gm in the researches of Messrs. Kundt and Warburg* 
gases. We must acknowledge, however, that these considera- 
tions Go not constitute sufficient proofs. 
On the other hand, there are some compound bodies whose 
ress densities are in contradiction with the principle of Avo- 
We should be forced to admit that all these compounds 
suffer decomposition when they seem to be reduced to vapor, 
so that, instead of measuring their volume, we measure that of 
their elements, -or of the products of their wr Sd pit 
Although this decomposition has been ascertained in some 
cases, it has not in one 
seen, the principle of Avogadro gives rise to 
serious objections, ihe without being convinced of its worth- 
lessness, like my eminent friend, M. Deville, I acknowledge 
that it is as yet but an hypothesis, in contradiction with facts, 
which have not been satisfactorily explained. But, I repeat 
Berichte der deutschen Chemischen Gesellschaft, 1875, p. 945. 
