Coewoss Neva) Periodic Law of the Chemical Elements. ne
‘were existing in the series of elements. - The discovery of
rew elements was uniquely the results of observations,
ind was made either by chance or by the extra powers of
‘hought and perception of the investigator. These discoveries
 did not offer any special philosophical interest ;
this is the reason we have seen such a small number of
‘nvestigators venture on the study of the elements, like
in exploring party in a new and unknown land, not
‘tnowing which way to turn; but now they will find that
‘his vast and important domain of chemistry is not entirely
 devoid of landmarks, but that the periodic law will
ierve as a guide, and will facilitate future discoveries.
[V. THE Use oF THE PERIODIC LAW FOR DETERMINING
THE PROPERTIES OF AS YET UNDISCOVERED
ELEMENTS,
The preceding developments show us that the periodic
.aw renders it possible for us to bring to light the untnown
 properties of elements whose atomanalogues are
town to us. Further, we can see, by referring to Tables
.» and IL, in which the periodic relations are shown, that
nany elements are missing, and we can confidently pre-1i&
 their discovery. I am therefore going to describe the
rroperties of several as yet undiscovered elements: by
‘his means I hope to show, in a new and perfectly clear
nanner, the exactitude of the law, although the confirma-:ion
 of these proofs is reserved for the future. Let us add
hat the previous determination of the properties of untnown
 elements will facilitate the discovery of these elenents,
 because knowing them we can foretell the reacions
»f their compounds.
So as to avoid introducing new denominations for the
inknown elements into science I shall designate them by
he name of the nearest lower analogue of the odd or even
:slements in the same group, and placing in front of this
word cne of the Sanscrit numbers (eka, dui, tri, tschatour,
%c.). The unknown elements of the first group will be
called ekacesium (Ec=175), duiceesium (Dc=220), &c,
f niobium, for example, were not known we could call it
tkavanadium. The denominations will show the analogies
very clearly ; the names, however, of the fourth series
1ave not this advantage, because they ought to be derived
tom those of the elements of the second series, and we
wow from Chapter I. that this typical series is not in
somplete atomic analogy with the fourth.
Besides, in this series there is only one missing element;
 it is in the third group, and is called ekaboron, Eb,
As it follows K=39, and Ca=40, whilst it precedes Ti=48,
ind V=31, its atomic weight should be about Eb=44;
ts oxide should be Eb,Ojg, but it should not have very
characteristic properties; it will form in all respe@s the
cransition from CaO to TiO; In its maximum salts,
EbXj, the equivalent of the metal will be about 3=44 ;
it will not, therefore, be lower than the equivalents of
hases which are already known; it will be intermediate
setween the equivalent of Mg=12, and that of Ca=20.
We have seen in the foregoing chapter that Yt=88 @)
D1=138(?), and Er=178 (?) belong to this same group.
However, the position of this latter is still very uncertain,
and the elements have not been sufficiently studied;
therefore the properties of Eb can only be determined by
means of its atomanalogy with the elements Ca and Ti
of the fourth series. The case of this element is therefore
more complicated than those of other unknown elements.
[n consideration of Ca and Ti oualy giving one stable
oxide in the air, we may admit that Eb will only give one
stable basic oxide, Eb,O3;. The oxide in its properties
sught to be to Al,O3 what CaO is to MgO, or what TiO,
is to SiOz; consequently it should Le a more energetic
base than aluminium, and at the same time it ought to
agree with Al not only in its forms of corresponding compounds,
 but also, in many cases, in its properties. Thus,
the sulphate Eb,(SO,); will not be such an easily soluble
sody as Al,(SO,)s, because sulphate of calcium is more
lifficultly soluble than sulphate of magnesium. - The base

THE CHEMICAL NEWS.

Vor. XLI. No. 1055.

[rT still remains for me to mention a possible modification
in the atomic weights of ytirium and of erbium (perhaps
also of terbium, if terbium is really an element existing in
nature). However, the history of these interesting elenents
 is still enveloped in darkness, according to the
rontradictory debates between Mosander and Delafontaine
n the one hand, and Bunsen and Bahr on the other
a2and ; they therefore require fresh researches. If we keep
‘0 the results obtained by these two last investigators, and
f we admit with them that the equivalent of Yt=30'85
‘Berzelius found 32-1 and 35°0, Bopp found 34, and Delafontaine
 found 32), and that the equivalent of Er=56-3,*
:xcept from any error resulting from them having been insufficiently
 studied, these elements can be placed in
Group III., which receives the highest forms of oxides,
such as R;03. Yttrium, with the atomic weight 88, would
come in the sixth series, immediately after Rb=85 and
5r=87, and consequently before Zr=go and Nb=g4;
therefore the equivalent of Yt would be = 29'3 = =
As it is very doubtful whether anyone has yet succeeded
n separating Yt from Ce, La, Di, Er (perhaps also from
Tb and Th), we can admit that the determinations of
Bunsen and Bahr coincide sufficiently with the theoretical
number.
This place for yttrium is justified, as the results of
applying the periodic law to the preceding elements show,
viz., by the strongly basic properties of the oxide, by the
aon-volatility of YtClg, by the composition of the sulphate,
Yt;50,)3,8H,0, similar to the composition of the sait
which didymium forms analogous to Yt, by the insolubility
of the fluoride, &c. The erbium of Bunsen and Bahr, if
we take their results as bordering on the truth, apparently
pelongs to Group III., Series 10, before La= 180, Ta=182,
and W=184, and it should possess the atomic weight
178; the form of the oxide is therefore R,0j3, and its
:quivalent = 59'3. We can explain the low number (563)
found by Bunsen by supposing that his erbium was not
free from yttrium.
To convince us of the exaétness of these modifications
of the atomic weights of Yt and of Er, we do not know
any fa&, as we do in the case of the metals of cerite;
nobody has determined either the density of their oxides, t
their behaviour in the presence of oxidising and reducing
agents, or the composition and the form of their double
salts. Here, then, more than in any other part of the
system, are researches, guided by the periodic law,
lecessary.
To give another example of the direGion in which researches
 on elements (based on the periodic law) should
se made, I propose to pass now to the determination of
:he properties of elements which are still undiscovered.
Without the periodic law, it would be absolutely impossible
 to foresee any of the properties of unknown elements ;
and, further, we could not form any idea of what gaps

* Erbium, according to Delafontaine, has an equivalent lower than
39°68. Bunsen thinks that Delafontaine was working with an impure
sample.
+ The number 48-4 given by Eckeberg for the oxide of yttrium
might be thought to relate to an impure substance. However, it
corresponds to the periodic law, for the volume of 2Sr0=8:,0,=49,
.he volume of Yt203=47, the volume of Zr,0,=45,