146 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[August 24, 1872. 
have only yet studied a few hundreds; hut the study of 
the composition and the mode of formation of these com -1 
pounds induces the conclusion, that nature has scarcely 
assigned a limit to their production. Already the bodies 
belonging to this class are ranged in series regulated by 
a very simple law of derivation, and a knowledge of some 
members of one of these series enables us to predict the 
composition and properties of members yet unknown. 
Further, the comparison of two of these series so esta¬ 
blished by means of a certain law demonstrates with the 
greatest clearness the existence of a series of which the 
members are yet wanting to us, and thus we see unrolled 
before our astonished eyes a glimpse of the infinite variety 
of combinations that hydrogen may form with carbon. 
These hydrocarbons appear under the most diverse 
forms. Some are transparent, colourless gases, resisting 
every attempt made to liquefy them; others, of which 
the boiling-point is often much below the freezing-point 
of water, only take tbe liquid form under the combined 
influences of strong pressure and a low temperature. 
A great number exist in the form of liquids, with tastes 
and odours the most diverse, boiling at all possible tem¬ 
peratures, from the heat of the hand to a red heat, or 
even not volatilizing at all without decomposition. 
Finally, others are solid bodies, colourless or coloured, 
crystalline or amorphous ; some fusible at greatly vary¬ 
ing temperatures, others infusible; some distilling 
or subliming at all possible temperatures; others 
breaking up variously under the influence of strong- 
heat : all differing from each other in taste and 
smell no less than do the gaseous and liquid car¬ 
bides. If the hydrocarbons were not distinguishable 
from other substances except by their number and the 
variety of their properties, these would entitle them to 
be looked upon as a group distinct from the rest of chemi¬ 
cal compounds; but they present yet other characters 
which furnish a no less powerful argument for separating 
them from the bodies Avhich constitute the other groups. 
Following the analogy of their composition, the mem¬ 
bers of this group of carbides present in the individual 
development of their properties an agreement which is 
not observed in the less extensive groups of combinations. 
Under the influence of elementary bodies, the hydro¬ 
carbons undergo numerous modifications. Oxygen and 
nitrogen especially, either alone or combined more or 
less with hydrogen, possess the faculty of entering into 
combination with the members of this group. There is 
thus formed an unlimited number of derivative com¬ 
pounds which, besides the carbon and hydrogen, con¬ 
tain nitrogen or oxygen, or both those elements at the 
same time, or other elementary bodies, such as chlorine 
and sulphur. The introduction of these elements into 
the hydrocarbons modifies the properties of the. latter, 
according to laws the determination of which is the pro¬ 
blem presented to the chemist. Already, for many 
years, the best methods of research have been applied to 
this study, and if the goal, such at least as is conceived 
by the enthusiastic searcher, is yet afar off, much has 
already been done towards attaining to it. Even now, to 
a certain extent, the changes in the properties of a carbide i 
which the introduction of an elementary body will 
cause can be determined beforehand. Numerous re- i 
searches have shown that the modifications that one of a 
series undergoes in certain circumstances are reproduced ! 
in the same circumstances upon all the members of the 
same series ; so that the conquest of a single fact often 
suffices to throw light upon a series of analogous ones. 
It follows naturally that each reaction modifying a hydro¬ 
carbon in any manner whatever, will produce, when 
applied to the other hydrocarbons, a class of derivative 
products between which there will be the same corres¬ 
pondence as between the carbides that gave them birth. 
There is thus formed, around each carbide, a symmetri¬ 
cal group of derivative compounds, and, the circle always 
increasing, each of these derivatives may in its turn 
become the centre of a new s.vstem of compounds. 
This is not the place to follow further the endless 
ramification of the hydrocarbons; it is rather sought 
to recall the exceptional character of the group, and to 
indicate, though only in a general way, what has led 
chemists to consider the hydrocarbons and their deriva¬ 
tives, as a whole, to be isolated and distinct from the 
other combinations. 
This group of bodies presents a new interest when it 
is known that it forms, in great part at least, the sub¬ 
stance of plants and the bodies of animals. The hydro¬ 
carbons and their derivatives are combustible. In 
contact with oxygen, under favourable circum¬ 
stances, they produce oxide of carbon, carbonic 
acid, and oxide of hydrogen or water; a portion only 
of the nitrogen oxidizes, the remainder is disengaged 
in the free state during combustion. Such is the 
manner in which the substance of plants and animals 
comports itself. The branch just torn from the tree 
soon undergoes change; the bark contracts, the leaf 
fades, and every trace of humidity disappears. If this 
dry wood be now heated, it will inflame and burn until 
there remains only a small grey or white mass of mineral 
substance, incapable of further alteration under the pro¬ 
longed action of heat. We say then that the wood has 
burnt, leaving nothing but ash. If a similar experiment 
be made with a substance of animal origin, a piece of 
meat for instance, the same phenomena are observed, 
and of the piece of meat nothing is left but the ash. 
That part of the wood, or the meat, which can be so 
burnt, consists of combinations of carbon, hydrogen, 
oxygen and nitrogen ; and these combinations in burn¬ 
ing, volatilize under the form of carbonic acid, water, 
binoxide of nitrogen or free nitrogen. 
This similitude of composition between organic matters 
and the hydrocarbons and their derivatives has led to 
the latter being designated the group of organic com¬ 
pounds. Moreover, it has been in studying the organic 
substances, plants and the bodies of animals, that the 
chemist has become acquainted with these carbides of 
which we speak. Not more than half a century since 
the name of chemistry of the organic compounds, or 
simply organic chemistry, taken from its origin, was 
given to this new branch of science. Thanks to the 
talent of the great chemists of this century and the zeal 
of their scholars, it has developed wonderfully and with 
marvellous rapidity. Even the first researches led to 
most unexpected results, and discoveries followed one upon 
another. The extraordinary number of compounds pro¬ 
duced by so small a number of elements captivated the 
interest of all. It was believed that those compounds 
formed an entirely new class of bodies, differing from 
mineral substances by their properties and composition, 
but above all by their mode of formation. As attempts 
to reconstitute from their elements these compounds ex¬ 
tracted from plants and animals were not at first success¬ 
ful their formation was attributed to the mysterious in¬ 
fluence of the vital force, and a boundary line was traced 
between the products of a mineral nature and those of 
an organic nature which was thought to he uncrossable. 
But this line of demarcation was only an artificial one; 
it has long since disappeared, effaced by new discoveries. 
Plants and animals no longer monopolize the secret of 
the formation of organic compounds; science has revealed 
it. By the aid of the elements alone, the chemist has 
been able to produce these bodies one after another with 
all the properties that they present when extracted from 
the living organism. And if some among them have 
hitherto escaped this synthesis, and cannot yet be pro¬ 
duced except under the influence of the vital forces ; if 
in many cases that result has only been obtained by ela¬ 
borate processes which nature produces in the most 
simple manner; nevertheless, known facts justify the 
hope that the difficulties met with in producing arti- 
fically certain bodies found in living organisms will be 
soon surmounted by the indefatigable zeal of chemists. 
(To be continued.) 
