56 J. W. Mallet on Osmious Acid. 
two equivalents is based upon very limited data, and can but be 
looked on as approximative merely. As regards osmium, Frémy — 
says that in several experiments he has obtained an equivalent | 
number lower than that given by Berzelius, and the vapor 
density of osmic acid, which we shall notice presently, points to © 
an equivaient close to 97. A re-determination of this equiv® ~ 
lent is very much to be desired. 
Taking the series as given above, we find ruthenium and 
osmium to fall in between phorphorus and arsenic—arsenic ant 
antimony; the numbers from phosphorus to antimony increas 
ing by 22—44—66—88, just as in the following group givel 
by Dumas: 
At. wts. 
Chromium, : ‘i . 
Molybdenum, - - - 26+22=48 
Vanadium, - - - 26+44=70 
Tungsten, - 2 - 26+66=92 
and we may arrange the two series in parallel lines, 
P (81) Ru (58) As (75) — Os (97) 
Cr (26) Mo (48) V (70) W (92) 
e 1es named in each of the two lines just given are 4 
homologous in many respects besides that of atomic weight, and 
