ELECTIVE ATTRACTION. 
In the expression of compound affinities, 
the sketches must either be made from ac- 
tual experiment in every instance, or by 
deduction from the numerical expressions 
of the forces of attraction. Some of the 
difficulties of effecting this have been men- 
tioned in the present article 5 but as a con- 
jectural set of numbers, inferred from such 
facts as we possess, may be useful in many 
instances to point out the probability of 
decompositions previously to trial, Guyton 
Morveau’s table of the numerical expres- 
sion of affinity between the alkalies and so- 
luble earths, and the five principal acids, 
is here inserted. 
TABLE VII. NUMERICAL EXPRESSION OF AFFINITIES. 
BY GUYTON MORVEAU. 
Sulphuric 
acid. 
Nitric 
acid. 
Muriatic 
acid. 
Acetic 
acid. 
Carbonic 
acid. 
Barytes 
66 
62 
36 
28 
14 
Potash 
62 
58 
32 
26 
9 
Soda 
53 
50 
31 
25 
8 
Lime 
54 
44 
23 
19 
12 
Ammonia.... 
46 
38 
21 
20 
4 
Magnesia 
50 
40 
22 
17 
6 
Alumine 
40 
36 
18 
15 
2 
The method of exhibiting simple or com- 
pound affinities by symbols, according to 
Bergman, consists in placing those sub- 
stances which are applied to each other up- 
on the same horizontal line of direction ; 
the component parts of tlie substances be- 
ing placed at the two extremities of a ver- 
tical bracket ; and the new products, if any, 
are placed one above the other, at the mid- 
dle part of a horizontal bracket, connect- 
ing their component principles. This will 
be rendered clearer by an example. 
I. Suppose magnesia to be presented to 
a solution of sulphat of potash, it will be 
found that no decomposition takes place. 
These facts are expressed as follows : 
'Potash 
Sulphat of 
potash Sulphuric 
^ acid Magnesia. 
In the above scheme, the sulphat of pot- 
ash is placed opposite the point of a verti- 
cal bracket, and its two component parts, 
potash and sulphuric acid, are placed witli- 
in the extremities of the same bracket. 
Horizontally opposite the sulphuric acid 
is placed magnesia, to denote, that it is 
presented to that acid. And as these two 
substances are not connected by a bracket, 
it is to be understood from the scheme, that 
they do not unite, and consequently that the 
sulphat of potash remains undecomposed. 
II. On the contrary, if to a solution of 
sulphat of magnesia, potash be added, a 
decomposition will ensue, which is ex- 
pressed as follows : 
Sulphat of 
magnesia < 
f Magnesia 
Sulphuric 
acid Potash 
A 
Sulphat of potash 
The arrangements in this scheme depend 
on the same principles as those of the fore- 
going : but the bracket underneath the sul- 
phuric acid and potash denotes, that these 
two substances unite, and form sulphat of 
potash, which is accordingly placed beneath 
the middle of the bracket. The point of 
the bracket being turned up, is made to 
denote that the compound remains suspend- 
