300 Prof. J. W. Mallet on the Chemical and 
The atomic weights of ruthenium and osmium are here assumed 
as 53 and 97; numbers not differing more widely from those 
commonly received—52°2 (Claus) and 99°6 (Berzelius)—than 
do several of those assumed by Dumas. Our knowledge of these 
two equivalents is based upon very limited data, and can but be 
looked on as merely approximative. Asregards osmium, Fremy 
says that in several experiments he has obtained an equivalent 
number lower than that given by Berzelius; and the vapour- 
density of osmic acid, which we shall notice presently, points to 
an equivalent close to 97. A redetermination of this equivalent 
is very much to be desired. 
Taking the series as given above, we find ruthenium and 
osmium to fall in between phosphorus and arsenic, arsenic and 
antimony,—the numbers from phosphorus to antimony increas- 
ing by 22—44—66—88, just as in the following group given 
by Dumas :— 
Atomic weights. 
Chromium . ... . 26 
Molybdenum. . . « 26422=48 
Vanadium . .. . 26444=70 
Tungsten. . . . . 26466=92 
and we may arrange the two series in parallel lines, 
P (31) Ru (53) As (75) Os (97) 
Cr (26) Mo (48) V (70) W (92) 
These numerical relations are of very little importance in 
themselves, when we employ the small numbers of the hydrogen 
scale of equivalents, and especially when we permit ourselves to 
alter the numbers themselves to any extent, however small; but 
they acquire more interest when they present us with groupings 
of elements which we acknowledge on other grounds to be natu- 
rally related. In such cases, when the homology is distinctly 
marked, we may even be justified in taking some liberties for 
the moment with the numbers standing, often with but slender 
evidence to support them, for the equivalents of the less- known 
elements; and we may, perhaps, thus be directed to errors of 
determination which future experiments will clear away. 
The bodies named in each of the two lines just given are 
homologous in many respects besides that of atomic weight, and 
a connexion between the two series, through vanadium, has 
lately been shown by Schafarik.. There is a clear resemblance 
running through the formule and properties of their oxides. In 
the chromium series—a very natural one—the most important 
oxides are the metallic acids of the composition MO®; we have 
also in each case a binoxide, MO?; but the sesquioxide is pro- 
