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plied, the first syllable of oxygen, with a termination (ide) indica-
tive of combination ; to which the name of the other element was
joined to express the specific compound. Thus a compound of oxy-
gen and hydrogen is oxide of hydrogen ; of oxygen and potassium,
oxide of potassium; of which compounds, the first, or water, is an
instance of a neutral oxide; and the second, or potash, of a base
or alkaline oxide. But the same elementary body often combines
with oxygen in more than one proportion, forming two or more
oxides; to distinguish which the Greek prefix {proto, Trpoiroe, first) is
applied to the oxide containing the least proportion of oxygen; deuto
(cturepoc, second) to the oxide containing more oxygen than the pro-
toxide ; and trito (rpi-oc, third) to the oxide containing still more
oxygen than the deutoxide; which last oxide, if it contains the
largest proportion of oxygen with which the element can unite to
form an oxide, is more commonly named the peroxide ; from/* 5 /*, the
Latin particle of intensity. Thus, the three compounds of the metal
manganese and oxygen are distinguished as follows :

Composition.

Names. Manganese. Oxygen.

Protoxide of manganese . . 100 28. ( J1

Deutoxide of manganese . . 100 43.36

Peroxide of manganese . . 100 57.82

As the prefix per implies simply the highest degree of oxidation,



114 CHEMICAL NOMENCLATURE AND NOTATION.

it may be applied to the second oxide where there are only two, as in
the oxides of iron, the second oxide of which is called, indifferently,
the deutoxide or peroxide of iron. M. Thenard, in his Traite de
Chimie, avoids the use of the term deutoxide, and confines the
application of peroxide to such of these oxides as, like the peroxide
of manganese, do not combine with acids. He applies the names
sesquioxide and binoxide to oxides, which are capable of combining
with acids, and contain respectively, once and a half and twice as
much oxygen as the protoxides of the same metal. He has thus the
protoxide, sesquioxide, and peroxide of manganese, the protoxide
and sesquioxide of iron, the protoxide and binoxide of tin, &c. This
distinction is useful, and will be adopted in the present work.
Certain inferior oxides, which do not combine with acids, are
called suboxides ; such as the suboxide of lead, which contains less
oxygen than the oxide distinguished as the protoxide of the same
metal.

The compounds of chlorine and several other elements are distin-
guished in the same manner as the oxides. Such elements resemble
oxygen in several respects, particularly in the manner in which their
compounds are decomposed by electricity. Chlorine, for example,
like oxygen, proceeds to the positive pole, and is therefore classed
with oxygen as an electro-negative substance, in a division of ele-
ments grounded on their electrical relations. Thus, with the other
elementary bodies,

Oxygen . . forms . . oxides,

Chlorine . . " ... chlorides,

Bromine . . bromides,

Iodine . " . iodides,

Fluorine . . fluorides,

Sulphur . . sulphides (or sulphurets),

Phosphorus . . phosphides (or phosphurets),

Carhon . . carhides (or carburets),

Nitrogen ... . nitrides,

Hydrogen . " . . hydrides,

Cyanogen (N C 2 ) . . cyanides,

Sulphion (S O 4 ) . " . . sulphionides.

As cyanogen and sulphion, although compound bodies, comport
themselves in their combinations like electro-negative elements, their
compounds are named in the same manner as the oxides.

When several chlorides of the same metal exist, they are distin-
guished by the same numerical prefixes as the oxides. Thus we
have the protochloride and the sesquichloride of iron ; the protochlo-



CHEMICAL NOMENCLATURE AND NOTATION. 115

ride, and the bichloride of tin. The compounds of sulphur greatly
resemble the oxides, but they have been generally named sulphurets,
and not sulphides or sulphurides. Berzelius, indeed, applies the
term sulphuret to such binary compounds of sulphur only as are basic
or correspond with basic oxides; while sulphide is applied by him
to such as are acid, or correspond with acid oxides. Hence, he has
the sulphuret of potassium, and the sulphide of arsenic and sul-
phide of carbon. Compounds of chlorine are distinguished by him
into chlorurets and chlorides, on the same principle ; thus he speaks
of the chloruret of potassium, and of the chloride of phosphorus.
But these distinctions have not served any important purpose, while
besides conducing to perspicuity it is an object of some consequence
in a systematic point of view to allow the termination ide, already
restricted to electro-negative substances, to apply to all of them with-
out exception.

The combinations of metallic elements among themselves are dis-
tinguished by the general term alloys, and those of mercury as
amalgams,

(b). The binary compounds of oxygen which possess acid properties
are named on a different principle. Thus the acid compound of tita-
nium and oxygen is called titanic acid ; of chromium and oxygen,
chromic acid; or the name of the acid is derived from that of the sub-
stance in combination with oxygen, with the termination ic. Where the
same element was known to form two acid compounds with oxygen, the
termination ous was applied to that which contained the least propor-
tion of oxygen, as in sulphurous and sulphuric acids. On the dis-
covery of an acid compound of sulphur which contained less oxygen
than that already named sulphurous acid, it was called hyposulplm-
rous acid, (from the Greek VTTO, under) ; and another new compound,
intermediate between the sulphurous and sulphuric acids, was named
hijposulphuric acid. On the same principle, an acid containing a
greater proportion of oxygen than that already named chloric acid
was named hyperchloric acid, (from the Greek vn-ep, over;) but
now more generally perchloric acid. The names of the different
acid compounds of oxygen and sulphur, which have been referred to
for illustration, with the relative proportions of oxygen which they
contain, are as follows:

Composition.

Names. Sulphur. Oxygen.

Hyposulphurous acid . . 100 . . 50

Sulphurous acid . . . 100 . . 100
Hyposulphuric acid . . 100 . . 125
Sulphuric acid ... 100 .. 150



116 CHEMICAL NOMENCLATURE AND NOTATION.

The same system is adopted for all analogous acids. An acid of
chlorine, containing more oxygen than chloric acid, is named per-
chloric acid, and other similar compounds, which all contain an un-
usually large proportion of oxygen, are distinguished in the same
manner ; as periodic acid, and permanganic acid. The perchloric acid
is also sometimes called oxichloric ; but this last term does not seem
so suitable as the first.

Another class of acids exists in which sulphur is united with the
other element in the place of oxygen. The acids thus formed are called
sulphur acids. The names of the corresponding oxygen acids are
sometimes applied to these, with the prefix sulph, as sulpharsenious
and sulpharsenic acids, which resemble arsenious and arsenic acids
respectively in composition, but contain sulphur instead of oxygen.

Lastly, certain substances, such as chlorine, sulphur and cyanogen,
form acids with hydrogen, which are called hydrogen acids, or
hydraclds. In these acid compounds the names of both constitu-
ents appear, as in the terms hydrochloric acid, hydrosulphufic acid,
and hydrocyanic acid. Thenard has proposed to alter these names
to chlorhydric, siilphohydricj and cyanhydric acids, which in some
respects are preferable terms.

2. Compounds of the second order, or salts, are named accord-
ing to the acid they contain, the termination ic of the acid being
changed into ate, and ous into ite. Thus a salt of sulphuric acid is
a sulphate; of sulphurous acid, a sulphite; of hyposulplmrous
acid, a hyposulphite; of hyposulphuric acid, a hyposulphate / and of
perchloric acid, a per chlorate ; and the name of the oxide indicates
the species as sulphate of oxide of silver, or sulphate of silver ; for
the oxide of the metal being always understood, it is unnecessary
to express it, unless when more than one oxide of the same
metal combines with acids, as sulphate of protoxide of iron, and
sulphate of sesquioxide of iron. These salts are often called proto-
sulphate and persulphate of iron, where the prefixes proto and per
refer to the degree of oxidation of the iron. The two oxides of iron
are named ferrous oxide and ferric oxide by Berzelius, and the
salts referred to, the ferrous sulphate, and the ferric sulphate. The
names stannous sulphate and stannic sulphate express in the same
way the sulphate of the protoxide of tin, and the sulphate of the
peroxide of tin. But such names, although truly systematic, and
replacing very cumbrous expressions, involve too great a change in
chemical nomenclature to be speedily adopted. Having found its
way into common language, chemical nomenclature can no longer be
altered materially without great inconvenience. It must be learned



CHEMICAL NOMENCLATURE AND NOTATION. 117

as a language,, and not "be viewed and treated as the expression of a
system. A .SV//YV- sulphate contains a greater proportion of acid than
the sulphate or neutral sulphate; a ~bi -sulphate twice as much, and a
twywj-aulphate once and a half as much as the neutral sulphate;
while a ,sv/ b -sulphate contains a less proportion than the neutral salt;
the prefixes referring in all cases to the proportion of acid in the
salt, or to the electro-negative ingredient, as with oxides. The
excess of base in sub-salts is sometimes indicated by Greek prefixes
expressive of quantity, as ^//-chromate of lead, *m-acetate of lead;
but this deviation is apt to lead to confusion. If a precise expres-
sion for such subsalts were required, it would be better to say, the
bibasic subchromate of lead, the tribasic subacetate of lead. But the
names of both acid and basic salts are less in accordance with correct
views of their constitution, than the names of any other class of com-
pounds.

Combinations of water with other oxides are called hydrates : as
hydrate of potash, hydrate of boracic acid.

3. In the names of quaternary compounds or of double salts,
the names of the constituent salts are expressed, thus : Sulphate of
alumina and potash is the compound of sulphate of alumina rand
sulphate of potash; the name of the acid being expressed only once,
as it is the same in both of the constituent salts. The name alum,
which has been assigned by common usage to the same double salt,
is likewise received in scientific language. The chloride of platinum
and potssium expresses, in the same way, a compound of chloride of
platinum with chloride of potassium. An'oxichloride, such as the
oxichloride of mercury, is a compound of the oxide with the chloride
of the same metal.

The first ideas of a chemical nomenclature are due to Guyton de
Morveau, whose views were published in 1782; but the chief merit
of the construction of the valuable system in use is justly assigned to
Lavoisier, who reported to the French Academy on the subject, in the
name of a committee, in 1787. It has not been materially modified
or expanded since its first publication. The present, or Lavoisierian
nomenclature, does not furnish precise expressions for many new
classes of compounds, the existence of which was not contemplated by
its inventors, and many of its names express theoretical views of the
constitution of bodies which are doubtful, and not admitted by all
chemists. But its deficiencies are supplied, and the composition of
bodies more accurately represented, in certain written expressions, or
chemical formulae, wliich are also employed to denote particular sub-



118 CHEMICAL NOMENCLATURE AND NOTATION.

stances, and winch form a valuable supplement to the nomenclature
still generally used. These formulae are constructed on the simplest
principles, and besides supplying the deficiencies of the nomencla-
ture, they at once exhibit to the eye the composition of bodies, and
afford a mechanical aid in observing relations in composition, of the
same kind as the use of figures in the comparison of arithmetical sums.
Symbols of the elements. Each elementary substance is repre-
sented by the initial letter of its Latin name, as will be seen by
reference to the table of elementary substances, page 108 ; but when
the names of two or more elements begin with the same letter, a
second in a smaller character is added for distinction ; thus oxygen
is represented by the letter O, the metal osmium by Os, fluorine by E,
and iron (ferrum) by EC; small letters, it is to be observed, never being
significant of themselves, but employed only in connexion with the large
letters as distinctive adjuncts. These symbols represent, at the same
time, certain relative quantities of the elements, the letter O express-
ing not oxygen indefinitely, but 100 parts by weight of oxygen, and
Ee 350 parts by weight of iron, or any other quantities of these two
substances which are in the proportion of these numbers : 8 parts
of oxygen, for instance, and 28 of iron. It will immediately be
explained that the elementary bodies combine with each other in
certain proportional quantities only, which are expressed by one or other
indifferently of the two series of numbers placed against the names
of the elements in the table referred to. These quantities are con-
veniently spoken of as the combining proportions, the equivalent
quantities, or the equivalents of the elements. The symbol, or letter,
of itself representing one equivalent of the element, several equivalents
are represented by repeating the symbol, or by placing figures before
it ; thus Ee Ee, or 2 Ee, and 3 0, mean two equivalents of iron and
three of oxygen. Or small figures are placed either above" or below
the symbol, and to the right; thus Ee 2 , and O 3 , or Ee 2 O 3 , are of
the same value as the former expressions, but are used only when
symbols are placed together in the formulae of compounds. Two
equivalents of an element are sometimes expressed by placing a dash
through, or under its symbol, but such abbreviations will not be
made use of in the present work.

Formula of compounds. The collocation of symbols expresses
combination : thus Ee O represents a compound of one equivalent or
proportion of iron, and one of oxygen, or the protoxide of iron ; SO 3 ,
a compound of one equivalent of sulphur, and three of oxygen that
is, one equivalent of sulphuric acid ; and sulphate of iron itself, con-



CHEMICAL NOMENCLATURE AND NOTATION. 119

sisting of one equivalent of each of the preceding compounds, may be
represented as follows :

Fe O S 3 , or

FeO + S O 3 , or

FeO, SO 3 .

The sign plus ( + ) or the comma, being introduced in the second
and third formulae, to indicate a distribution of the elements of the
salt into its two proximate constituents, oxide of iron, and sulphuric
acid, which is not so distinctly indicated in the first formula. It may
often be advantageous to make use of both the comma and the plus
sign in the same formula, and then it would be a beneficial practice
to use them as in the following formula for the double sulphate of
iron and potash :

FeO, S0 3 +K0, S0 3 ,

in which the comma is employed to indicate combination more
intimate in degree, or of a higher order than the plus sign, namely,
of the oxide with the acid in each salt, while the combination of the
two salts themselves is expressed by the sign + .

The small figures in the preceding formulae affect only the symbol
or letter to which they are immediately attached. Larger figures
placed before and in the same line with the symbols apply to the
compound expressed by the symbols. Thus 3 S O 3 , means three
equivalents of sulphuric acid ; 2 Pb O, two equivalents of oxide of
lead. But the interposition of the comma or plus sign prevents the
influence of the figure extending farther, thus
2 Pb 0, Cr 3 , or
2Pb + Cr O 3 ,

is two proportions of oxide of lead, and one of chromic acid, or the
sub-chromate of lead. To make the figure apply to symbols which
are separated by the comma or plus sign, it is necessary to enclose all
that is to be affected within brackets, and place the figure before
them. Thus,

2 (Pb 0, Cr O 3 )

means two proportions of neutral chromate of lead. The following
formulas of two double salts with their water of crystallization, exhibit
the application of these rules :

Iron-alum, or the sulphate of peroxide of iron and potash :

KO, SO 3 + Fe 2 3 , 3S0 3 + 24 HO
Oxalate of peroxide of iron and potash :

3 (K O, C 2 3 ) +Fe 2 O 3 , 3 C 2 O 3 -t-6 HO.

It will be found to conduce to perspicuity, to avoid either connecting
two formulae of different substances not in combination, by the sign



120 CHEMICAL NOMENCLATURE AND NOTATION.

plus, or allowing them to be separated merely by a comma, as the
plus and comma between symbols or formulas are conventionally
understood to unite the formulae into one, and to express com-
bination ; and indeed it is advisable to write every complete formula
apart, and in a line by itself, if possible.

The only other circumstance to be attended to in the construction
of such formulae is the arrangement of the symbols or letters, which
is not arbitrary. In naming a binary compound, such as oxide of
iron, chloride of potassium, &c., we announce first the oxygen or
element most resembling it in the compound ; that is, the electro-
negative ingredient ; but in the formulas of the same bodies, it is the
other or the electro-positive element which is placed first, as in Fe O,
and K Cl. In the formulae of salts, it is likewise the basic oxide or
electro-positive constituent which is placed first, and not the acid.
Thus the sulphate of potash is K 0, S 3 , and not S O 3 , K 0.
Information respecting the constitution of a compound may often be
expressed in its formula, by attending to this rule. Thus sulphuric
acid of specific gravity 1.780, contains two proportions of water to
one of acid, but by giving to it the following formula :

HO, S0 3 + H0,

we express that one proportion only of water is combined as a base
with the acid, and that the second proportion of water, the formula
of which follows that of the acid, is in combination with this sulphate
of water.

The above system of notation is complete, and sufficiently con-
venient for representing all binary compounds, and compounds
belonging to the organic department of the science, in the formulae
of which the ultimate elements only are expressed. But when
salts and double salts are expressed, the formulae sometimes become
inconveniently long. They may often be greatly abbreviated, and
made more distinct, by expressing each equivalent of oxygen in an
oxide or acid, by a point placed over the symbol of the other element,
thus :

Protoxide of iron, Fe.

Sulphuric acid, S.

Crystallized sulphate of protoxide of iron, Fe S, H-f 6H.

Alum, KS, Al Al S 3 + 24H.

Felspar, K Si, Al Al Si 3 .

Oxalate of peroxide of iron and potash, 3K CC + Fe Fe, 3CC + 6H.
Such formulae are more compact, and more easily compared with each



COMBINING PROPORTIONS. 121

other, the relation between the mineral felspar and alum without
its water of crystallization, being seen at a glance on thus placing
their formulae together ; the one having the symbol for silicium, the
other that for sulphur, but everything else remaining the same. This
abbreviated plan also exhibits more distinctly the relation between
the equivalents of oxygen in the different constituents of a salt, which
is always important.

It is to be observed, that the oxygen expressed by the points
placed over a letter is brought under the influence of the small figure
attached to that letter : as, for example, S 3 in the preceding formula
of alum, means three equivalents of sulphuric acid ; so that this sign

has the same value as if it were written 3 S.

Equivalents of sulphur are likewise sometimes expressed by
commas placed over other symbols, as the trito-sulphuride of arsenic

by As ; but such compounds are not of constant occurrence like the

oxides, and do not create the same necessity for a new and arbitrary

symbol. A compound body, such as cyanogen, which combines with

a numerous series of other bodies, is often for brevity expressed by

the initial letter or letters of its name, as

Cyanogen . Cy,

Ethyl . E ;

and the organic acids are sometimes expressed by a letter in the same
way, but with the minus sign ( ) placed over it : thus

Acetic acid, by A,

Tartaric acid, by T.

But arbitrary characters of this kind will always be explained on the
occasion of their introduction.

SECTION II. COMBINING PROPORTIONS.

All analyses prove that the composition of bodies is fixed and
invariable: 100 parts of water are uniformly composed of 11.1 parts
by weight of hydrogen, and 88.9 parts of oxygen, its constituents
never varying either in nature or proportion. This and other sub-
stances may exist in an impure condition, from an admixture of
foreign matter, but their own composition remains the salne in all
circumstances. It is this constancy in the composition of bodies
winch gives to chemical analyses all their value, and rewards the vast
care necessarily bestowed upon their execution.

An examination of the composition of a class of bodies, such as the
oxides, containing an element in common, shows that any one element
unites with very different quantities of the other elements. Thus in



12S



COMBINING PROPORTIONS.



eacli of the five oxides of which the composition is given below, the oxy-
gen and other constituents appear in a different relation to each other :

Composition of Oxides.



Water.


Oxide of Copper.


Oxide of Zinc.


Oxide of Lead.


Oxide of Silver.


Oxygen . 88.9
Hydrogen 11.1

100


Oxygen . 20.2
Copper . 79.8

100


Oxygen 19.1
Zinc . 80.9

100


Oxygen 7.2
Lead . 92.8

100


Oxygen . 6.9
Silver . 93.1

100



But the relation between the oxygen and the other constituent in
these oxides will be seen more distinctly by stating their composition
in such a way as to have the oxygen expressed by the same number
in every case, or made equal to 100 parts. Thus :

Composition of Oxides.



Water.


Oxide of Copper.


Oxide of Zinc.


Oxide of Lead.


Oxide of Silver.


Oxygen 100
Hydrogen 12.5

112.5


Oxygen . 100
Copper . 396

496


Oxygen 100
Zinc . 406

506


Oxygen 100
Lead . 1294

1394


Oxygen . 100
Silver . 1350

1450



From which it follows, that

12.5 parts of hydrogen,
396 parts of copper,
406 parts of zinc,
1294 parts of lead,
1350 parts of silver,

combine with 100 parts of oxygen.

These numbers prove to be in some degree characteristic of the
substances to which they are here attached, for when the composition
of the sulphides of the same substances is examined, it is found
that exactly corresponding quantities of hydrogen, copper, &c. like-
wise combine with one and the same quantity of sulphur, although
not with 100 parts of that element as of oxygen. The conclusion
from an*examination of the sulphides is, that

12.5 parts of hydrogen,
396 parts of copper,
406 parts of zinc,
1294 parts of lead,
1350 parts of silver,

combine ivith WM parts of sulphur.



COMBINING PROPORTIONS. 123

An examination of the chlorides of the same five elements likewise
proves, that

12.5 parts of hydrogen,
396 parts of copper,
406 parts of zinc,
1294 parts of lead,
1350 parts of silver,

combine with 443.75^;#r,9 of chlorine.

Hydrogen, copper, &c. are indeed found to unite in the propor-
tions repeated above, with a certain or constant quantity of all other
elements; as, for example, with 97 8 bromine, with 1580 iodine, &c.
On extending the inquiry to other substances, it appears that for
each of them a number may be found which expresses in like manner
the proportion in which that substance unites with 300 parts of
oxygen, 200 of sulphur, 443.73 of chlorine, &c. These numbers con-
stitute the combining proportions, or equivalent quantities of bodies,
which are introduced in the table of the names of the elements at the
beginning of this chapter, and which are the quantities understood to
be expressed by the chemical symbols of these bodies.

Any series of numbers may be chosen for the combining propor-
tions, provided the true relation between them is preserved, as in the
first series of numbers given in the same table, which are all 12 \
times less than the numbers of the second series. Hydrogen is
reduced from 12.5 to 1, oxygen from 100 to 8, sulphur from 200 to
16 : altered in the same proportion, copper becomes 31.66, zinc 32.52,



Online LibraryThomas GrahamElements of chemistry, including the applications of the science in the arts → online text (page 12 of 60)