398 J. P. Cooke on the Numerical Relations 
molybdate of lead from Rezbanya, which he supposed to be a 
chromate ; but the fact has been disproved by G. Rose, who has 
shown that the supposed chromate isa molybdate mixed witha 
small amount only of chromate. There seems, nevertheless, to 
series, since chromic acid is i8omorphous with sulphuric acid. 
or the present, however, we must regard them as sub-series, 
related, but distinct, the second being in ameasure supplementary 
to the first. ‘They are distinguished in the table by printing the 
names of the second sub-series a little to the right of those of the 
first, and the fact that their atomic weights are intermediate to 
those of the first, I have indicated to the eye by giving to the 
names also an intermediate position. ; 
The analogies between oxygen and sulphur are so numerous, 
that, were we to place oxygen in but one series, we should place 
it in this. HO and HS, HO: and HSs2, resemble each other very 
closely, as do also the oxygen salts the corresponding sulphur 
salts. Moreover, there can be no doubt in regard to the isomorph- 
ism of the two elements, since it has been established upon the 
authority both of Mitscherlich and Becquerel, and from two dif- 
ferent compounds. The only doubtful case in the series was that 
of vanadium, which in some of its properties resembles arseme 
more closely than it does molybdenum. The reasons for giving 
it the place which it occupies were the facts that its acids corres 
pond to those of molybdenum, and that it forms remarkably 
highly colored oxyds which are repeated also in molybdenum. It 
is trne that the properties of the element itself are not those we 
should expect from the position which ‘it ocenpies in our table ; 
yet, if it were placed in the Six Series, it would fall between 
phosphorus and arsenic, which on-the whole it resembles less 
than it does molybdenum, for although it is combustible, yet 
neither it nor its oxyds are volatile. I consider it, therefore, 48 
a member of the Eight Series, but affiliating very closely with 
the Six. Its atomic weight favors this hypothesis. Vavadate of 
# See G. Rose's Mineral System. 
