between the Equivalent Numbers of Elementary Bodies. 101 
organic radical mereur-ethyl, C,H,Hg, analogous to zinc-ethyl, 
C,H, Zn. is compound has recently been isolated by Buck- 
ton.* Silver does not appear to be capable of a similar substi- 
tution; when chlorid of ethyl is made to react upon zinc-ethyl 
the products are ethyl, chlorid of zinc and metallic silver. It 
has lately been shown by Hallwachs and Schafarik that mag- 
nesitm forms an ethyl-magnesium.+ These metals are likewise 
all volatile, and it has been shown by H. St.C. Deville that mag- 
nesium, like the others, is readily distilled. 
It is not a little curious that the numerically negative mem- 
bers of this series lead into the positiye members of the fore- 
ad if we continue the subtraction of 44, we find for the 
equivalent for arsenic given by L. Gmelin, viz. 75:4, accords 
more nearly with some of these series and renders them more 
exact than that adopted by the Jahresbericht which has been 
here employed. 
e members of these two analogous series are further united 
by the fact that all of them, eleven in number, are capable of 
uniting with the hydro-carbons of the methyl, ethyl, &. ty 
to form powerful organic metals, and that this capacity appears 
to be limited to these elements alone.t 
(2.) 
each other by isom m. The equivalents of these me 
‘ccording to the most recent determinations, are as follows: 
Magnesium, 12 Chromium, 26-7 
Manganese, 27-5 Zine, 86 
Tron, Cadmium, 56° 
Cobalt, 295 Copper, 31° 
Nickel, 296 Lead, 103% 
ranium, 60 
[Some of the elements here enumerated are found also in the 
foregoing or following series. It need scarcely be remarked 
that no absolute classification into groups is possible; lead for 
instance is in some of its combinations isomorphous with the 
barium group, in others with the magnesia, copper in grey cop- 
* See this Journal, [2], xxviii, 146. + This Journal, [2], xxviii, 147. 
: t There a : jeve that an ethyl-aluminum may exist, 
_ Which would form an ence is fe p Papen If so, the pas property may (ere 
others of the metals of the earths. 
