22 
NOTES AND ABSTRACTS IN CHEMISTRY AND PHARMACY. 
On Acetylene. 
This gas has excited an unusual amount of interest among chemists since its 
isolation by M. Berthelot. To a great extent this is due, no doubt, to its being 
the only compound which can be obtained by the direct union of carbon and 
hydrogen. M. Berthelot effected its production, it will be remembered, by 
heating carbon to incandescence in an atmosphere of hydrogen by the voltaic 
arc. It then became the most natural starting-point from wdiich to effect the 
synthesis of organic compounds from the inorganic elements. At the same time 
it became known that most organic compounds furnish acetylene when exposed 
to a red-heat. It was found in coal gas, and was obtained by transmitting the 
gaseous hydrocarbons, or the vapours of alcohol, wood spirit, aldehyd, ether, 
etc., through red-hot tubes. It was also got by passing electric sparks through 
the same substances. Fortunately, acetylene possesses very distinctive charac¬ 
ters. It has a peculiar odour, and is readil}'' absorbed by certain metallic solu¬ 
tions, especially by the ammonio-subchloride of copper, with which it forms the 
very characteristic red precipitate of acetylide of copper. It is mainly owing to the 
delicacy of this reaction that the general formation of acetylene at high tempe¬ 
ratures has been so easily recognized. M. Berthelot states that a single drop of 
the reagent introduced into fifty cubic centimetres of hydrogen containing a 
thousandth part of acetylene is immediately covered with the characteristic red 
film. This is equal to the twentieth of a milligramme; but M. Berthelot adds 
that he can even detect a ten-thousandth part in fifty cubic centimetres of hy¬ 
drogen, which is equal to the two-hundredth of a milligramme. 
M. Berthelot has recently published'^ some curious and interesting experi¬ 
ments, showing that acetylene is always produced during the imperfect combus¬ 
tion of the ordinary hydrocarbons, and, in fact, of almost any organic body. 
The following are some of these experiments :— 
Into a gas jar, containing about 300 cubic centimetres of olefiant gas, is 
poured a little ammoniacal solution of subchloride of copper ;t the gas is 
lighted, and the jar is inclined and revolved so as to spread the solution over 
the interior of the jar, and allow the flame to enter. A very abundant red pre¬ 
cipitate is formed, both below the flame and in contact with it. 
With marsh gas the result is similar but less striking. 
The most brilliant effect, however, is obtained by the employment of ordinary 
ether. A few drops of ether are introduced into a gas jar, similar to the one 
used in the preceding case; two or three cubic centimetres of ammoniacal solu¬ 
tion of cuprous chloride are added, the ether is lighted, the jar inclined almost 
horizontally and turned round; the entire inner surface is immediately coated 
with a blood-red deposit of acetylide of copper. Hydride of amyl gives an 
equally good result, and in fact the experiment succeeds with any volatile liquid 
that does not mix with the reagent. M. Berthelot also demonstrates the produc¬ 
tion of acetylene during the burning of hydrocarbons, by showing its presence in 
the products of combustion from any smoky flame. A funnel is fixed at a little 
distance over the flame, and, by means of an aspirator, a gas bottle is filled with 
the gaseous products. Some of the cuprous solution is then poured in, and the 
red precipitate at once obtained. Berthelot has obtained this result from the 
flames of a variety of substances, including ether, benzol, oil of turpentine, stearic 
acid, oils, and naphthaline. 
* Comptes Rendus and Bull, de Soc. Cliiin. 
t This_ reagent may be made and used as follows:—A solution of chloride of copper is 
mixed with an equal volume of hydrochloric acid, and shaken with copper filings (or the 
copper precipitated from a solution of sulphate by a sheet of zinc) till it is colourless. Am¬ 
monia is tlien added to this solution, while it is out of contact with air, as otherwise it 
greedily absorbs oxygen, and forms the ordinary blue liquid. 
