5 
glass. As the electric relations of the elementary bodies 
exercise the greatest influence on their chemical relations, 
it may he stated generally, that the metalloids and acid¬ 
forming metals are electro-negative, and that the other 
base-forming bodies are electro-positive. 
A few iron ores exhibit magnetic properties, and 
indeed the compact magnetic ironstone not only attracts 
such bodies as are being capable of being attracted by the 
magnet, but sometimes possesses the power of making 
those magnetic. Besides native iron, titanic iron, mag¬ 
netic iron ore, and magnetic pyrites, nickel and cobalt, 
as they are obtained by reducing their ores, are also 
capable of being attracted by the magnet. The expe¬ 
riment may be tried either with the electrometer, or with 
an artificial magnet, which can be made at any moment, 
by rubbing a knife, or other steel instrument, with a natural 
or artificial magnet. 
Heat expands all minerals more or less; the native 
metals are affected by it to the highest degree, the crys¬ 
tallised compact oxidised substances to a somewhat smaller 
extent. This peculiarity is specially to be borne in mind 
in finding specific gravities, hence it is usual to maintain 
the temperature at a mean of 60° Fahr., or to reduce the 
results to 32°. Many minerals melt on being heated, and 
their fusibility may be determined either by comparison 
with other known substances, or by the thermometer. 
Others volatilise or burn on being heated, as is shown by 
their deportment before the blowpipe and in the retort. 
It must, however, be borne in mind, that the admission or 
exclusion of air exercises a very powerful influence on the 
results. 
CHEMICAL RELATIONS OF MINERALS. 
Minerals are either simple or compound; the former 
are called elementary, the latter compound bodies. The 
number of elements, according to the latest discoveries, 
has gradually increased to sixty-four, whereof, however, 
only some two-thirds play an essential part in the mineral 
kingdom, and of these, again, only a few enter into the 
composition of rocks. 
In the following table a view of these bodies is given, 
together with their properties and appearances, and at the 
same time their chemical symbols and equivalents, or 
atomic weights, are appended; their electrical relations 
are also indicated in the following manner:— 
1. Those bodies which exhibit negative electricity are 
marked —, and usually form acids with oxygen ; to these 
belong the metalloids without exception, and many of the 
allied metals. 
2. Those which exhibit positive electricity are marked 
thus +, and form bases with oxygen. 
3. Those + — or —f, form with oxygen sometimes 
bases and sometimes acids. The combining proportions, 
or equivalents, of the simple bodies, are those proportions 
by weight in which they combine, or have combined with 
others; and it is usual to calculate these from hydrogen, 
the atomic weight of which is set down as 1, or from 
oxygen, the weight of which is taken at 100. It is also 
usual, for the sake of brevity, to employ the symbol of each 
element indicated, and this usually consists of the initial 
letter of its Latin name. Thus, for example, the equi¬ 
valent of hydrogen is 1, that of oxygen is 8; then water, 
the commonest and first compound of these two elements, 
consists of one equivalent of hydrogen, and one equivalent, or 
eight parts by weight of oxygen; in the deutoxide of hydro¬ 
gen, on the other hand, there are two equivalents or sixteen 
parts by weight of oxygen ; the chemical formula for water 
must therefore be HO, or it may be more shortly expressed 
by putting down one equivalent of hydrogen, and setting- 
over it a point, thus, H; that for deutoxide of hydrogen 
must be H0 2 , or H. Thus, further, one equivalent of 
sulphur, 16, unites with one equivalent of oxygen, 8, and 
with it forms its first oxygen compound, hyposulphurous 
acid, SO, or S; with two equivalents of oxygen, it forms 
sulphurous S0 3 or S, and wdth three of oxygen, sul¬ 
phuric acid, S0 3 or S. It follows as a consequence, that 
in all combinations of sulphur with oxygen the amounts 
of oxygen are in simple proportions to one another, that 
is, they are double, triple, or the like multiples of the first 
simple combining number; this is called the law of mul¬ 
tiple proportions. The same law holds with all other 
combinations, simple or compound, which may be esti¬ 
mated in a similar manner, according to the number of 
equivalents of oxygen, hydrogen, or sulphur. 
The oxygen compounds, or oxides, as they are called, 
play an important part in nature generally, insomuch as 
the mineral elements composing the greatest part by hulk 
of the earth’s surface are oxides, such, for example, as the 
clays, limes, siliceous and talcose earths, water, etc.; -while, 
on the other hand, the pure elements, such as carbon, sul¬ 
phur, and the native metals, only enter into it in smaller 
quantities, and the compounds of chlorine and sulphur are 
almost invisible. 
The oxides are divided, as above mentioned, into bases, 
like the earths, alkalis, and basic oxides of the heavy metals, 
and acids. The former always contain a smaller quantity, 
one, one and a half, or at most two equivalents of oxygen ; 
the latter, one and a half, two, two and a half, three, or 
five equivalents of oxygen; and in doubtful cases, the 
compounds containing more oxygen, like the more nega¬ 
tively electric bodies, are generally considered acids. 
The compounds of sulphur with the heavy metals are 
called generally sulphur ores, and more particularly pyrites, 
and glance, if they present a metallic lustre, or blendes and 
cinnabars, if they are clear and of adamantine lustre. 
The same law of composition holds here as with oxygen, 
so that if a body, P, unites with one equivalent of oxygen 
in the oxide PO or P, it also unites with one equivalent 
of sulphur, and forms with it the metallic sulphuret PS 
r 
or P. It is usual, for shortness, to distinguish such com¬ 
pounds of sulphur with a dash over the initial letter of the 
element, and two equivalents of sulphur with two dashes, 
while double equivalents of the element may be expressed 
by a dash through its initial letter P. Thus, if Fe repre¬ 
sents iron, Fe 2 may be indicated by Fe. 
For further details reference must be made to any 
of the chemical and mineralogical text-books. 
As the purposes to which minerals may be applied, as 
well as the knowledge of individual species, stand in very 
close relation to their chemical composition, it is important 
to acquire dexterity in the analysis of minerals, and for 
this purpose either the moist or dry method may be 
c 
