OF THE ATOMIC WEIGHT OF ALUMINUM. 
1033 
Bearing of final result upon “Prout’s law.” 
It is interesting to observe that this result also adds one to the cases already on 
record of the numbers representing carefully determined atomic weights approaching 
closely to integers, and leads to a word on the reconsideration of “ Prout’s law.” The 
recent researches of Mr. Lockyer, not unsupported by evidence drawn from other 
sources, have tended to suggest the possibility, at least, that the forms of matter 
which as known to us under ordinary conditions we call elements may be susceptible 
of progressive dissociation at enormously high temperature, and, under circumstances 
in which this supposed state of dissociation admits of being spectroscopically observed, 
some of the characteristic features in the spectrum of what is usually known to us as 
hydrogen become in a very remarkable degree prominent. If such dissociation may 
really occur, and if the atoms of hydrogen as commonly known to us form either the 
last term, or any term not far removed in simplicity from the last, in the progressive 
breaking up of other forms of matter, it is obvious that “ Prout’s law,” or some modi¬ 
fication of it, such as was many years ago suggested by Dumas, must be true, the 
atomic weights of all the other so-called elements must be multiples of that of 
hydrogen, or multiples of that fraction of the hydrogen atom which may result from 
the dissociation of this body itself. If such fraction be very small as compared with 
the effect of the inevitable errors of experiment, the experimental verification or refuta¬ 
tion of the law will prove impossible, but if it be considerable, as for instance one-half 
of the commonly known hydrogen atom, or one-fourth, as assumed by Dumas, the 
question admits of practical examination. 
Well deserved attention has for some years past been given to the labours of Stas 
in this direction, and his main result is no doubt properly accepted, if stated thus, 
that the differences between the individual determinations of each of sundry atomic 
weights which have been most carefully examined are distinctly less than their differ- 
ence, or the difference of their mean, from the integer (or one-half or one-fourtli unit 
which Prout’s law would require. 
But the inference which Stas himself seems disposed to draw, and which is very 
commonly taken as the proper conclusion from his results, namely, that Prout’s law is 
disproved, or is not supported by the facts, appears much more open to dispute. 
It must be remembered that the most careful work which has been done by Stas 
and others only proves by the close agreement of the results that fortuitous errors 
have been reduced within narrow limits. It does not prove that all sources of constant 
error have been avoided, and indeed this never can be absolutely proved, as we never 
can be sure that our knowledge of the substances we are dealing with is complete. 
Dumas’ late observations on the occlusion of oxygen by metallic silver constitute an 
illustration of this, some of the best of Stas’ results being thereby undeniablv 
vitiated, though probably to but a minute extent. 
6 R 
MDCCCLXXX. 
