73
KG
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(gfemfiic Cfu6 (geprinfs jto. 15.
THE
ELECTROLYSIS
OF
ORGANIC COMPOUNDS
PAPERS
BY
HERMANN KOLBE
\\
(1845-1868)
PUBLISHED BY THE ALEMBIC CLUB.
Edinburgh Agent :
WILLIAM F. CLAY, 18 TEVIOT PLACE.
London Agents :
SIMPKIN, MARSHALL, HAMILTON, KENT, & CO. LTD.
I OCX).
KG)
PREFACE.
THE decomposition of organic compounds by electrolysis
is a subject that has engaged the attention of chemists
for more than half a century. The investigation of the
subject has enabled the synthesis of a variety of important
and interesting substances to be effected ; and, in the
hands of Kolbe especially, it was also of great service in
the development of certain theoretical views concern-
ing organic compounds. The present reprint contains
Kolbe's account of his earliest experiments which have
any bearing on the matter, as well as his classical memoir
upon the electrolysis of valerianates and acetates, and it
thus furnishes the first chapters in the history of this line
of investigation. Readers who are unfamiliar with the
formulae generally employed by Kolbe will find it useful
to recollect that the atomic weights of carbon, oxygen,
and sulphur are, with him, 6, 8, and 16 respectively.
The ''barred" formulae (made use of in one of the
papers only) coincide exactly with those employed later
without bars.
A few obvious misprints in the originals have been
corrected.
L. D.
95771
THE ELECTROLYSIS OF ORGANIC
COMPOUNDS.
EARLY EXPERIMENTS.
WHAT would appear to be the earliest references
by Kolbe to the effects of electrolysis upon
solutions of organic substances, are found in his paper,
" Contributions to the Knowledge of Conjugated Com-
pounds," printed in the Annalen der Chemie und Phar-
inacie, Vol. 54 (1845), PP- 145-188. At the time at
which this paper appeared, it seems as if Kolbe only
regarded the application of electrolysis to such solutions
as a means of submitting the dissolved substances to the
reducing influence of hydrogen at the moment of its
liberation. The following references are made in the
paper to the reducing effects of the galvanic current :
At pp. 155-156, where he states the effects of various
reducing agents upon sulphite of perchloride of carbon,
C GUSCX, (Trichlormethyl-sulphonyl chloiide), in con-
verting it into a substance which he calls sulphite of
chloride of carbon, and to which he assigns the formula
CeSO,, he says:
" Hydrogen brings about the same reduction when it
comes into contact, in the nascent state, with dissolved
sulphite of perchloride of carbon ; for example, when
iron or zinc is digested with an acidulated solution of
that compound in highly diluted alcohol ; or when the
same liquid is decomposed by the galvanic current.*
* In order to guard against the compound being oxidized by the
oxygen separated at the anode, the anode must be an easily oxidized
metal. I employed amalgamated zinc plates.
6 Kolbe.
The hydrogen vSet free in the process always has a peculiar
unpleasant smell."
At pp. 168-169, m the section on chlor-elayl hypo-
sulphuric acid, HO -f C.,H.,GlS L ,O 5 (Chlormethyl-sulphonic
acid), he says :
" Metallic zinc dissolves in chlor-formyl hyposulphuric
acid * with the evolution of hydrogen and the formation
of chloride of zinc ; the product is a mixture of the
zinc salts of chlor formyl hyposulphuric and chlor-elayl
hyposulphuric acids. The separation of the second
equivalent of chlorine from the chlor-formyl hyposul-
phuric acid clearly takes place, therefore, with greater
difficulty than the elimination of the first equivalent.
In that decomposition there is always a small part only
of the chlor-formyl hyposulphuric acid converted into
the compound richer in hydrogen. More of it is ob-
tained when the evolution of hydrogen is maintained
for a longer time by the addition of another acid sul-
phuric acid, for example ; but even in this way the last
portions of the chlor-formyl hyposulphuric acid cannot
be entirely removed. This succeeds only by the de-
composition of the acidulated solution of a salt of
chlor-formyl hyposulphuric acid or of sesquichloro-carbo-
hyposulphuric acid t by means of the galvanic current.
I proceeded according to the following method :
About 50 grms. of sesquichloro-carbohyposulphate of
potash were dissolved in water, mixed with sulphuric
acid, and digested with zinc until the liquid was quite
saturated with zinc salts. The solution of the metal
takes place with brisk evolution of hydrogen gas, which
diffuses abroad, during the process, a peculiar disagree-
able smell possessing some similarity to that of sulphuret
* [HO + CoHL>S 2 O 5 (Dichlormethyl-sulphonic acid).]
t [HO + C 2 i 3 S.,O 5 (Trichlormethyl-sulphonicacid).]
Electrolysis of Organic Compounds. J
of carbon. The greater part of the zinc crystallises out
as sulphate of zinc and potash when the hot concentrated
solution cools. The liquid poured off from this is pre-
cipitated, boiling, with carbonate of potash, filtered, and
evaporated to dryness, and the powdered residue is
extracted with boiling alcohol of 80. The dry saline
mass which remains behind after the evaporation of the
alcohol consists of a mixture of chlor-formyl and chlor-
elayl hyposulphates of potash. The quantity of the latter
is further increased by another similar treatment with zinc
and sulphuric acid. I then dissolved the residue, which
only contained a little chlor-formyl hyposulphuric acid,
in water again, made it slightly acid with sulphuric acid,
and submitted it, in a suitable vessel, to the decomposing
action of the galvanic current generated by two cells of
the Bunsen zinc-carbon battery. The electrodes were
two amalgamated zinc plates.
The operation is interrupted when the evolution of
hydrogen gas, which is brisk at first, ceases, and metallic
zinc is deposited upon the anode. The dissolved zinc
salts are precipitated by means of carbonate of potash,
and the filtered and acidulated solution is again decom-
posed by the current ; and this is repeated about three or
four times, or until all has been converted into chlor-
elayl hyposulphuric acid."
At pp. 174-176, in describing the preparation of methyl
hyposulphuric acid, HO + C.,H 3 S.,O 5 (Methyl sulphonic
acid), he says :
"I employed sesquichloro carbohyposulphate of potash
for its preparation.
70 grms. are dissolved in three times this quantity of
water, and the neutral liquid is decomposed, in the same
manner that I stated under chlor-elayl hyposulphuric
acid, by the galvanic current from two cells of a Bunsen
zinc-carbon battery. Two amalgamated zinc plates served
8 Kolbe.
as electrodes. The decomposition proceeds quietly and
without evolution of gas at first, with a somewhat con-
siderable elevation of temperature. Only after a large
part of the sesquichloro-carbohyposulphuric acid is con-
verted into methyl hyposulphuric acid does hydrogen
become free at the cathode. This circumstance can be
made use of in order to determine at any time, approxi-
mately at least, how much chlorine has been exchanged
for hydrogen.
According to the formula :
KO f C,e4 3 S 2 O 5 ) ( KO + C 2 3 S 2 O 5
6Zn \ = { 6ZnO
60 I
it is calculated that 57 grms. of zinc are necessary for the
conversion of 70 grms. of sesquichloro-carhohyposulphate
of potash. The deflection of the magnetic needle of a
Weber's tangent galvanometer introduced into the circuit,
amounted in these experiments, on the average, to be-
tween 50 and 60, which corresponds, in the case of
the instrument employed, to an average strength of
current of about 82. Since with this strength of current,
about 10 grms. of zinc are dissolved in an hour, the above
decomposition would be finished in 6 hours.
After the action of the current for one hour, the liquid
was so saturated with chloride of zinc that metallic zinc
was deposited upon the cathode in large quantity. It
was therefore precipitated, boiling, with carbonate of
potash ; the filtered alkaline solution was evaporated to
the original volume and exposed anew to the action of
the current for an hour, until the quantity of the separated
carbonate of zinc had increased so greatly that reduction
upon the cathode ensued.
It was only after 45 grms. of zinc, from the anode, were
dissolved, in the course of repeated operations, that a
Electrolysis of Organic Compounds. 9
disengagement of hydrogen commenced at the other
pole. The dissolved salts were now chlor-elayl hypo-
sulphate and methyl hyposulphate of potash, mixed with
a large excess of the chloride of potassium produced.
In order to separate the latter as much as possible, I
evaporated the solution to dryness and treated the residue
with boiling alcohol of 80. After the alcohol was dis-
tilled off, the soluble salts were again mixed with water
and, after the addition of a little carbonate of potash,
again decomposed by the current until 40 grms. of zinc
were dissolved afresh. The evolution of hydrogen was
very brisk at the end.
After the decomposition had continued altogether for
TO hours, I felt sure that the chlor-elayl hyposulphuric
acid was completely converted into methyl hyposulphuric
acid.
It is a remarkable phenomenon that in the decom-
position of an acid solution of sesquichloro carbohypo-
sulphate of potash by means of the galvanic current, the
exchange of the chlorine for hydrogen is at an end with
the formation of chlor-elayl hyposulphuric acid, whereas,
in presence of free alkali it extends to the third equi-
valent of chlorine also ; for I have never obtained a
trace of methyl hyposulphuric acid in the first case. It
is difficult to explain to one's self why the hydrogen
exerts towards chlorine, as soon as the acid to be decom-
posed is united to a base, a greater attraction than it does
when the acid is presented to it in the free state."
10 Kolbe.
OBSERVATIONS ON THE OXIDIZING
POWER OF OXYGEN WHEN DIS-
ENGAGED BY MEANS OF VOLTAIC
ELECTRICITY.*
IN describing in a former paper f the properties of
sesquichloro-carbohyposulphuric acid, I stated that
this body resists the action of the most powerful oxidizing
agents, such as chromic acid, nitric acid, and even nitro-
hydrochloric acid. I likewise stated the change it
undergoes by the action of a voltaic current, when an
easily oxidizable metal is used for the positive pole. By
this means another copulated acid is produced, in which
one or more equivalents of chlorine are replaced by
corresponding proportions of hydrogen.
I have since observed that this acid is completely
decomposed on employing two platina plates as elec-
trodes ; by which arrangement oxygen is disengaged at
the positive pole. The following details, which contain
a more perfect account of this observation, I hope will
be acceptable to the Society.
On decomposing a concentrated solution of sesqui-
chloro-carbohyposulphate of potash by a strong voltaic
current (obtained by four elements of Bunsen's battery),
at the commencement no hydrogen can be observed at
the negative pole in consequence of the formation of the
above-mentioned copulated acids, whilst chlorine, carbonic
acid, and afterwards oxygen, are evolved at the positive
pole. At the moment decomposition commences a
* [From Memoirs and Proceedings of the Chemical Society of
London. Vol. 3 (1848), pp. 285-287. Read December 7, 1846.]
f Liebig's Annalen der Chemie, liv. pp. 156, 160.
Electrolysis of Organic Compounds. 1 1
distinct acid reaction of the solution is perceptible,
owing to the formation of free hydrochloric and sulphuric
acids ; in a later stage of the process, these acids in-
creasing in quantity, hydrogen appears at the negative
pole, until finally, after all the hydrochloric acid has
been decomposed, and the disengagement of chlorine
has ceased, small octahedral crystals of perchlorate of
potash are deposited from the solution, which now con-
tains a large amount of free sulphuric acid and bisulphate
of potash. The formation however of perchloric acid in
this process is always preceded by that of chloric acid ;
for on evaporating the solution in an earlier stage of the
decomposition, beside the before-mentioned octahedral
crystals, the well-known rhombic plates of chlorate of
potash are obtained.
The following formula represents the most probable
decomposition sesquichloro-carbohyposulphuric acid un-
dergoes by the action of a voltaic current :
I~20|2CO,
Ud.
Tne production of perchloric acid in an acid solution
is certainly a fact worthy of attention, for according to
all the observations hitherto made, combination between
chlorine and oxygen could only be effected in presence
of a free alkaline basis ready to unite with the newly
formed acid ; but ascertained as it is by a great number
of careful experiments, it is another proof of the un-
paralleled negative power of oxygen when evolved by
means of voltaic action.
These observations induced me to make the following
experiments.
A neutral solution of chloride of potassium was decom-
posed in the same manner by a strong voltaic current ;
1 2 Kolbe.
it immediately became alkaline, whilst hydrogen and
chlorine were disengaged. The formation of chlorate of
potash, which took place under these circumstances, can
evidently be considered only as the result of the ordinary
chemical action of chlorine upon caustic potash. On
mixing however a solution of chloride of potassium with
sufficient sulphuric acid to set free all the muriatic acid,
and passing the voltaic current through it as before,
chlorate of potash was nevertheless formed, which was
subsequently converted into perchlorate of potash.
The transformation of oxy-acids of chlorine, such as
liquid hypochloric acid (CIO.,), or of a solution of chlorate
of potash, into perchloric acid by means of voltaic action,
has been mentioned by Berzelius. I have ascertained,
moreover, that when a voltaic current is passed through
hydrochloric acid, especially when previously mixed with
some sulphuric acid, free chloric and perchloric acids
are formed, after the disengagement of a considerable
quantity of chlorine.
A concentrated solution of chloride of ammonium
evolves hydrogen at the negative pole but neither oxygen
nor chlorine at the positive pole. But the surface of the
platina plate representing the latter pole is covered with
small yellowish oily drops of chloride of nitrogen, which
as soon as the two poles are brought into contact decom-
poses with a more or less violent explosion, chlorine and
nitrogen being evolved. This experiment illustrates at
once the formation of this compound and its highly ex-
plosive character.
Cyanide of potassium if dissolved in water is easily
oxidized by a voltaic current, and converted into cyanate
of potash, but I did not succeed in obtaining a per-
cyanate of potash. I was not more successful in en-
deavouring to form a fluorate of potash from the fluoride
of potassium by the same means.
Electrolysis of Organic Compounds. 13
I have not prosecuted my experiments further upon
inorganic substances, having from some observations on
the behaviour of organic compounds under the action of
the voltaic current obtained results of so much greater
interest, as to induce me to give them my exclusive
attention ; and at a future time, when I have completed
the investigation, I shall beg leave to communicate it to
the Chemical Society.
ON THE DECOMPOSITION OF VALE-
RIANIC ACID BY THE VOLTAIC
CURRENT.*
THE very remarkable changes which a series of
organic compounds undergoes by means of the
voltaic current, have induced me to make that mode of
decomposition the subject of a thorough investigation.
As however the numerous difficulties which present them-
selves in researches of this nature, and the immense"
extent of the field which opens before us, do not admit
of the results being communicated in a complete and
connected form, I beg to lay before the Chemical Society
a short preliminary notice of the changes which valerianic
acid undergoes when exposed to the oxidizing action of
the voltaic current, reserving a more complete description
of the products obtained till the investigation shall have
been brought to a close.
When the voltaic current, excited by six pairs of
Bunsen's carbo-zinc battery, is permitted to act on a
concentrated neutral solution of valerianate of potash in
* [From Memoirs and Proceedings of the Chemical Society of
London, Vol. 3 (1848), pp. 378-380. Read April 19, 1847.]
14 Kolbe.
the cold, two plates of platinum forming the electrodes,
a brisk evolution of gas takes place simultaneously from
both ; the gases evolved consist of hydrogen, carbonic
acid and a new carbo-hydrogen, but contain no traces
of oxygen gas as long as the solution of valerianate of
potash does not become too much exhausted. At the
same time a light oily liquid separates at the surface,
having an agreeable ethereal odour, and the alkaline
solution ultimately consists chiefly of carbonate and
bicarbonate of potash, the latter of which generally
separates during the operation in a crystalline form.
The neutral aethereal oil is a mixture of two com-
pounds ; the one containing oxygen, the other perfectly
free from it. By the action of an alcoholic solution of
potash the former is decomposed, and the latter can
then, by means of water, be separated unchanged. In
the pure state it exists in the form of a light colourless
aethereal oil, possessing an agreeable aromatic smell. It
is insoluble in water, but soluble in alcohol and aether ;
it boils at 108 C. without decomposition, and has the
composition C 8 H 9 . Oxygen and iodine are without
action upon it, but chlorine, bromine, and fuming nitric
acid form with it products of substitution.
The oil containing oxygen, which in the first instance
was found mixed with this substance, I have not yet
been able to obtain in a pure state ; but several circum-
stances render it more than probable that it is formed by
the union of valerianic acid with the oxide of the above
carbo-hydrogen. An alcoholic solution of potash treated
with it is found to contain as a product of decomposition
a considerable amount of valerianate of potash. But on
account of the small quantity of material which has been
at my disposal, I have not succeeded in separating the
alcohol C 8 H 10 O L) , which must have been formed at the
same time,
Electrolysis of Organic Compounds. 15
The gaseous carbo-hydrogen, which is evolved with the
hydrogen, is a substance analogous to defiant gas ; it is
characterized by a peculiar aethereal smell, and has a
specific gravity double that of olefiant gas. It unites
with chlorine even in the dark, forming a heavy oily
liquid, having a marked similarity to chlorelayl, and is
generally composed of a mixture of several products of
substitution. Its rational composition is expressed by
the formula C 8 H 8 . The changes which valerianic acid
undergoes, in accordance with the foregoing experiments,
are capable of a very simple explanation, if we consider
that acid as a conjugated combination of the carburetted
hydrogen, or the radical C 8 H 9 with oxalic acid, in a
similar manner to the new view taken of the constitution
of acetic acid. For whilst by the addition of one atom
of oxygen oxalic acid becomes converted into carbonic
acid, this radical is set free ; but a portion of it unites
with the excess of oxygen to form an oxide, and this
enters into combination with a portion of undecomposed
valerianic acid, giving rise to a new aether, C 8 H 9 O -f-
C 8 H 9 C 2 O 3 .
Another portion of the radical is probably decom-
posed at the moment of its formation, in consequence
of the concomitant evolution of heat into hydrogen and
the gaseous carbohydrogen C 8 H 8 . This latter view is
supported by the fact, that if the temperature of the
solution of valerianate of potash exceeds a certain point
during the decomposition, not a single drop more of the
retherial oil is produced.
The following formula will throw light on this decom-
position :
KO + C 8 H 9 C 2 O 3 \ _ / KO + 2 CO 2
O J-\C 8 H 9 .
Both butyric and acetic acids are acted on in a similar
1 6 Kolbe.
manner to valerianic acid ; the products of decomposition
of acetic acid are all gaseous, and appear to contain
oxide of methyl. Butyric acid gives in addition to the
gaseous compounds a volatile oil composed of C 6 H 7 .
The minute description of this product will form the
subject of a future memoir.
The foregoing investigation has been carried out during
the late session in the laboratory of Dr Lyon Playfair, as
whose assistant I have been engaged during that time ;
and I cannot allow this opportunity to pass by without
thanking him for the kindness and liberality which he
has shown in placing his laboratory at my disposal, in
leaving so much of my time on my own hands, and in
rendering me every assistance in his power.
Electrolysis of Organic Compounds. 17
RESEARCHES ON THE ELECTROLYSIS
OF ORGANIC COMPOUNDS.*
THE following investigation has chiefly arisen from
some former observations! respecting the trans-
formations of chloro-carbo-hyposulphuric acid, hydro-
chloric acid, and several other substances under the
influence of oxygen, when liberated in the circuit of the
galvanic current.* The facility with which, particularly
the former acid, resisting in the moist way the most
powerful oxidizing processes, is decomposed under these
circumstances, appears to point to electrolysed oxygen as
one of the most valuable oxidizing agents which are at
the disposal of the chemist. Its application in chemical
decompositions acquires additional importance, since its
intensity may be varied, either by concentrating and
* [From The Quarterly Journal of the Chemical Society of
London, Vol. 2 (1850), pp. 157-184.]
t Observations on the oxydizing action of oxygen when dis-
engaged by means of voltaic electricity in the " Memoirs and Pro-
ceedings of the Chemical Society," vol. in. p. 285.
J In the above cited investigation it was intended to state, that
in the oxidation of hydrochloric acid by means of the electrical
current, chloric acid appears at the positive pole even without the
presence of an alkali. The sense of the sentence has been seriously
altered by a misprint on page 287, line 8 from the top, hypochloric
having been substituted for "hydrochloric acid." The sentence
should have been as follows : "I have ascertained that when a
voltaic current is passed through hydrochloric acid, especially when
previously mixed with some sulphuric acid, free chloric and per-
chloric acids are formed after the disengagement of a considerable
quantity of chlorine."
B
1 8 Kolbe.
heating the liquid, or by increasing or diminishing the
number of elements producing the electrical current.
Starting from the hypothesis that acetic acid is a con-
jugated compound of oxalic acid and the conjunct methyl,
I considered it, under these circumstances, not at all
improbable that electrolysis might effect a separation of
its conjugated constituents, and that, in consequence of
a simultaneous decomposition of water, carbonic acid, as
a product of the oxidation of oxalic acid, might appear at
the positive, while methyl, in combination with hydrogen,
viz., as marsh-gas, would be observed at the negative
pole.
The decomposition, which actually takes place, is not
in perfect accordance with this supposition, as will be
seen by the experiments hereafter described. The results
obtained, however, are by no means less interesting, and
deserve particular attention, opening as they do a pros-
pect that the electrolytical decomposition of organic
compounds will afford most important disclosures with
reference to their chemical constitution.
After having made some preliminary experiments with
several acids belonging to the acetic acid series, the pro-
ducts of the oxidation of valerianic acid appeared parti-
cularly suited for minutely following out the course of
this decomposition. I therefore consider it convenient,
first to describe the phenomena attending the decom-
position of this acid, inasmuch as they form the basis for
further experiments.
ELECTROLYSIS OF VALERIANIC ACID.
Valerianic acid being, like acetic acid, a bad con-
ductor of electricity, I employed in the electrolytical
decomposition a concentrated solution of its potash salt,
prepared by neutralizing carbonate of potash, free from
Electrolysis of Organic Compounds. 19
chloride, with pure valerianic acid, distilling at 175
(347 F.)*
The decomposing apparatus, Fig. i,f is a glass cylinder,
ii inches in height and 2\ inches in diameter, which
may be closed by means of a cork ; in this is fastened a
cylinder of sheet copper, closely approaching the sides of
the glass, and to which is soldered the copper wire a,
slightly projecting from the vessel. Within the copper
sheet is another cylinder of platinum foil of somewhat
smaller diameter, terminating in the platinum wire b, and
prevented contact with the copper by a narrow ring of
glass, placed between the two cylinders at their lower
extremities. Both wires, as well as the large delivery
tube c, are cemented perfectly air tight into the cork, the
tube being of sufficient diameter to admit of emptying
and filling the cylinder without inconvenience.
On passing the electrical current, produced by four
elements of Bunsen's zinco-carbon battery, through the
apparatus filled to the height c c, with a concentrated
solution of valerianate of potash, the platinum wire b
forming the positive pole, the negative wire being in
connexion with the cylinder of copper, the following
phenomena are observed : A lively evolution of gas takes
place simultaneously with the formation of yellowish oily
drops, possessing an agreeable etherial odour ; on agita-
* The presence of chloride of potassium gives rise to the for-
mation of secondary chlorinated products requiring more minute
investigation. The soda salt cannot be employed with advantage,
inasmuch as the bicarbonate, which is formed during the decom-
position, enfeebles to a great extent the electrical current, inter-
rupting it entirely towards the end of the process. The bicarbonate
of potash being more soluble, a few crystals only separate during
the decomposition.
t [The accompanying figure illustrates Kolbe's paper in Liebig's
Annalen, Vol. 69. It was more suitable for reproduction than the
one in the Chemical Society's Journal.]
Electrolysis of Organic Compounds. 21
tion with the liquid, the oil remains undissolved, even on
the addition of potash.
The remarkably odorous gases which are evolved
during the process, contain, after complete expulsion of
air from the apparatus, no longer a trace of oxygen,
and may be ignited without fear of explosion. Carbonic
acid and hydrogen, however, are present in considerable
quantities, in conjunction with a third gas burning with
a highly luminous flame, and imparting to the mixture its
peculiar odour.
After the action of the current had been continued for
several hours, the stratum of oily liquid on the surface
had increased to the height of several lines, while the
valerianate of potash was almost completely converted
into a mixture of carbonate and bicarbonate of potash,
the latter generally crystallizing towards the end of the
operation.
With a view of ascertaining at which pole each of
these products was liberated, I endeavoured to separate
the electrodes by means of a porous diaphragm, which
allowed me to collect separately the substances disen-
gaged at either pole. I employed for this purpose a
porous cell of clay, into which a small glass tube of
nearly equal diameter, and open at both ends, was
fastened air tight by means of a caoutchouc joint. This
arrangement containing the platinum foil, forming the
positive pole, and admitting of being closed by a cork
furnished with a delivery tube, was introduced into the
copper cylinder of the decomposing apparatus.
Both cylinders were now filled with a solution of the
neutral valerianate to the height of about one inch above
the caoutchouc joint. It was found that on closing the
circuit, only hydrogen and free potash were disengaged at
the copper pole, while all the other products, the etherial
oil, carbonic acid, the odorous gas, and the free acid,
22 Kolbe.
(which, in this arrangement, prevented the formation of
a carbonate.) appeared at the positive pole.
VALYL.
In the experiments instituted for the preparation* of
the etherial oil, I preferred removing the product from
time to time with a pipette, which I introduced through
the open glass tube c, the process being continued until
the solution was entirely exhausted of valerianic acid.
The alkaline residue was now again introduced into a
porcelain dish, and neutralized with pure valerianic acid ;
the neutral solution being again repeatedly subjected to
the process of electrolysis, until a sufficient quantity of
oil had been collected.
The impure product, after repeated agitation with
water, exhibits the following properties : It is miscible
with alcohol and ether in all proportions, insoluble in
water, and of lower specific gravity than that liquid. It
possesses an agreeable etherial odour. Chloride of
calcium is dissolved by it, particularly in the cold, and
hence the slight turbidity which is observed when the
clear anhydrous liquid is subjected to ebullition. It
commenced boiling a few degrees above 100 (212 F.),
the temperature rapidly rising to 160 (320 F.) and even
higher ; the last products possess a penetrating disagree-
able odour, and differ in a remarkable manner from
the liquid which passed over at a lower temperature.
The quantity of carbon found in the distillate, collected
at different temperatures, diminishes with the rise of the
boiling point, decreasing from 80 to 76 per cent., while
* The decomposing apparatus employed in this and the following
experiments, was placed in a vessel of water at the temperature of
o C. The solution of valerianate of potash being moderately
heated, hardly a trace of the oil is produced, the decomposition
taking place in an entirely different manner.
Electrolysis of Organic Compounds. 23
the amount of oxygen, varying between 6 and 10 per cent,
is found in the inverse proportion. The disagreeably
smelling oil distilling towards the end of the operation,
appears to be formed only by the action of chloride of
calcium on the original compound ; but even when dis-
tilled in vacuo at very low temperatures, the distillates
collected at different stages of the process exhibit a com-
position not less variable.
It appears that the impure oil is a mixture of at least
two substances, its deportment with an alcoholic solution
of potash affording a powerful argument in favour of this
opinion.
On boiling a mixture of this oil with an alcoholic
solution of potash in a flask connected with the lower
extremity of a Liebig's condenser, placed in such a posi-
tion as continually to return the condensed products to
the boiling fluid, the following phenomena are observed.
Immediately on the application of heat, bubbles of a
gaseous body are seen to rise, possessing the characteristic
odour of the compound, which, in the electrolytical de-
composition of valerianate of potash, accompanies the
evolution of hydrogen and carbonic acid : hence, it
appears that this gas, which is held in solution by the
liquid, becomes liberated when heat is applied. In a
short time the evolution ceases, and the odour of the gas
is no longer perceptible ; when in a full state of ebullition
the oil, previously colourless, assumes a yellowish tint,
and becomes slightly turbid, while a heavy, apparently
oily liquid collects at the bottom of the flask, which on
examination is found to be an aqueous solution of vale-
rianate of potash. To effect complete decomposition of
the constituent affected by potash, at least half an hour's
ebullition is necessary.
On mixing the liquid after boiling, with a large excess
of water, a light etherial oil separates, which, after stand-
24 Kolbe.
ing for some time, collects on the surface into a clear
transparent layer ; repeatedly washed with fresh portions
of water, and subsequently dried by chloride of calcium,
it exhibits a pretty constant boiling point at 108 (226.4
F.). The fraction distilling at this temperature, when
subjected to a second rectification boiled at the same
point, the first three-fourths of the product being col-
lected. The quantity of pure substance thus obtained
exceeds half the original volume of the impure oil. The
purified compound presents itself in the form of a clear
pellucid fluid of agreeable odour, and first insipid, though
afterwards of a burning taste ; miscible with alcohol and
ether in all proportions, it is perfectly insoluble in water,
which readily precipitates it from its alcoholic and etherial
solutions. It boils exactly at 108 (226.4 F.), distilling
without change to the last drop. It is inflammable,
and burns with a strongly luminous smoky flame. It
dissolves chloride of calcium, but to a less extent than
the impure oil. Its specific gravity at 18 (64.4 F.) is
0.894, that of the vapour being 4.053.
By combustion with oxide of copper* the following
results were obtained :
I. 0.1825 grm. of substance gave
0.5630 ,, ,, carbonic acid, and
0.2610 ,, ., water.
* It is impossible to burn this substance, so rich in carbon, with
either protoxide of copper or chromate of lead alone, a small quantity
of metallic carbide being formed, which occasions a deficiency in
the carbon amounting to between 0.5 and 0.8 per cent. ; hence
combustion with oxygen is absolutely necessary, the latter being
conveniently evolved from small pieces of perchlorate of potash
placed at the posterior end of the combustion tube, a plug of dry
asbestos preventing contact with the protoxide of copper. In addi-
tion to this precaution, it is necessary to attach to the common
bulbs a tube containing solid potash, in order to absorb the aqueous
vapour volatilized in the gases passing through the potash apparatus,
Electrolysis of Organic Compounds. 25
II. 0.1578 grm. of substance gave
0.4855 ,, ,, carbonic acid, and
0.2260 water.
These numbers lead to the formula
C 8 H
Theory. Experiment.
8 equiv. of Carbon . 600.0 84.2 8.4. r 84.0
9 Hydrogen . 112.5 *5 8 I S-9 i5- 8
712.5 100.0 100.0 99.8
This compound possesses the composition of the,
hitherto hypothetical, radical of the still unknown alcohol
belonging to butyric acid (C S H 9 O,HO), or the radical
which, in valerianic acid, we assume to be in combina-
tion with oxalic acid. I propose to call it valyl.
Without entering here minutely into the question,
whether valyl is indeed the radical of an alcohol corre-
sponding to methyl, ethyl, and amyl ; I will only mention
one fact, which, in support of such a supposition, may
seem of some importance ; viz. that the specific gravity
of its vapour exactly coincides with the number indicated
by theory. According to the analogy of the methyl and
ethyl series this compound would contain 4 vol. of carbon
vapour, and 9 vol. of hydrogen condensed into i vol.,
hence the density of its vapour would be 3.9387, viz. :
4 vol. of Carbon . . . 3.3168
9 ,, ,, Hydrogen . . . 0.6219
i vol. of Valyl .... 3.9387
Experiment gave the following results :
Substance employed . ...... , I.;. 0.2085 g rm -
Volume of vapour observed . * 63.30:
Temperature . < . ..-. , . - ... i . 1 33.3 C.
Barometer ..... 752.9 mm
Mercury-column .... 64.0"""
Pressing oil-column at 17 C , 262, o mm
26 Kolbe.
The specific gravity of valyl vapour as calculated from
the foregoing numbers is 4.053, closely coinciding with
the theoretical value.
Valyl is difficultly acted on by oxidizing agents ;
moderately strong nitric acid, or a mixture of chromate
of potash and sulphuric acid have very little action upon
it even after continuous ebullition ; strong fuming nitric
acid, however, especially after the addition of sulphuric
acid, completely oxidizes this compound, nitrous fumes
being evolved, while the oil gradually disappears. On
neutralizing with carbonate of baryta, evaporating the
filtrate to dryness, and extracting the residue with strong
boiling alcohol the nitrate of baryta remains undissolved.
The alcoholic liquid when evaporated leaves a saline
residue, the distillation of which, with sulphuric acid,
yields a yellow acidulous liquid, possessing in an eminent
degree, the characteristic odour of butyric acid. On
neutralizing the solution with freshly precipitated car-
bonate of silver, and filtering whilst boiling, a crystal-
line silver salt is deposited on cooling, which is readily
darkened by exposure to light, or by continued ebullition
with the mother liquor. The dry salt does not detonate
when heated. The potassium, barium, and lead salts,
do not appear to crystallize; want of material has pre-
vented me from determining the composition of this
acid, and of its salts by analysis ; considering, however,
the mode of its formation, the peculiar and unmistake-
able odour of butyric acid, and its yellow colour, it
becomes very probable that this compound is a mixture
of butyric acid, and of nitrobutyric acid.
corresponding to nitro-metacetonic acid,
Electrolysis of Organic Compounds. 27
The following equation represents the transformation
of valyl into butyric acid.
C 8 H 9 + 5 O - HO, (C G H r ) C 2 O 3 + HO.
Valyl. Butyric acid.
Dry chlorine has no action on valyl in the dark, the
minutest ray of light, however, suffices for the immediate
production of hydrochloric acid vapours, while chlori-
nated substitution compounds are simultaneously formed.
By an excess of chlorine the liquid gradually becomes
converted into a semi-fluid almost viscid mass : direct
combination of chlorine and valyl, without elimination of
hydrogen does not occur under these circumstances.
The action of bromine on valyl, although less powerful,
is attended with similar phenomena ; iodine is dissolved
in considerable quantity by it without however entering
into combination ; sulphur likewise has no action upon it.
The decomposition of valerianic acid into valyl and car-
bonic acid, with the simultaneous evolution of hydrogen
is represented by the following equation :
HO, (C 8 H 9 ) C 2 O 3 - C 8 H 9 + 2 CO., + H.
Valerianic acid. Valyl.
which is so extremely simple, that further elucidation
would be superfluous were not other products formed
at the same time. In order clearly to understand this
peculiar reaction, we must direct our attention to the
study of the two bodies occurring with it ; viz. : the
oxygenated constituent of the impure oil, and the odorous
gas evolved with the carbonic acid. If we consider the
fact of the elimination of valyl at the oxygen pole of the
battery, the idea naturally suggests itself, that a partial
oxidation of it into oxide of valyl may there be effected
the supposition, however, that the original oil consists
28 Kolbe.
of a mixture of valyl and its oxide is immediately dis-
countenanced by its peculiar deportment with an alco-
holic solution of potash, unable, as we are, to understand
what kind of compound would be thus produced. The
potash solution with which the oil had been boiled, when
diluted with water to separate the valyl, evaporated to
dryness, and distilled with sulphuric acid, was found to
contain a considerable quantity of valerianic acid. The
presence of this acid may be most easily explained, by
assuming the existence and decomposition in the liquid,
of a valerianic ether, an assumption which would lead us
to consider the oxygenated constituent of the original oil
as valerianate of oxide of valyl. The formation of this
ether will be easily understood, if we bear in mind, that
together with valyl and oxygen, valerianic acid is likewise
liberated at the positive pole simultaneously with oxide
of valyl in the nascent state.
It is true, that in the above decomposition by an
alcoholic solution of potash, according to the analogy of
the compound ethers generally, hydrated oxide of valyl
should have been liberated.
If, however, and it can hardly be doubted, the hydrated
oxides of amyl, valyl, and ethyl, present the same rela-
tion with reference to their miscibility with water, as do
valerianic, butyric, and acetic acids, the ratios of whose
solubility are inversely as their atomic weights, it is at
once intelligible why, with so small a quantity of sub-
stance at my disposal, I did not succeed in separating
the hydrated oxide of valyl from a liquid containing
alcohol in solution.
The presence of this compound, however, was proved
to a certain extent by the following observations. The
alcohol containing valerianate of potash was diluted with
water to separate the valyl, and distilled off from the
valerianate, On introducing the first portion of the
Electrolysis of Organic Compounds. 29
distillate into a boiling mixture of bichromate of potash
and dilute sulphuric acid, a product passed over, possess-
ing in an eminent degree the characteristic odour of both
butyric and acetic acids. A further confirmation of this
view of the composition of the crude oil is afforded by
analysis.
The substance for investigation was repeatedly washed
with water, (first with a dilute alkaline solution), dried
over chloride of calcium, and distilled in vacuo at a low
temperature.
0.1175 g rm - of the distillate gave
0.3320 ,, ,, carbonic acid, and
0.1475 wat er.
corresponding to the following composition per cent. :
Carbon . . . 77.0
Hydrogen . . 13.8
Oxygen . . .9.2
100. o
If, starting with the formula C 8 H 9 O, (C 8 H 9 ) C, O,
for the oxygenated oil, we calculate from the quantity of
oxygen found, the per-centage of carbon and hydrogen
belonging to this compound, we arrive at the following
composition :
18 equivs. Carbon . . .31.0
1 8 ,, Hydrogen . . 5.1
4 Oxygen . . .9.2
45-3
by subtracting these numbers from the above we obtain
carbon and hydrogen exactly in the proportion required
by the composition of-valyl (C 8 H 9 ).
Experiment. Theory.
Carbon . . . 46.0 46.1
Hydrogen . - . 8.7 8.6
3O Kolbe.
A similar mixture, prepared at a different period, when
subjected to combustion gave the following numbers :
0.2647 rm - of substance gave
0.7600 carbonic acid, and
0.3420 ,, ,, water.
and a similar calculation leads us to the following results :
Composition of CompOSl-
vjri-gjl. tijjrf Theory.
Carbon . . 78.3] (25.0! 53.3 53.4
Hydrogen . 14. 3 [ minus 4-2- = 10.1 10.0
Oxygen . . 7.4) ( 7.4]
100.0 36.6 63.4 63.4
It now only remains to determine the nature of the
gas evolved with carbonic acid, in the decomposition of
valerianate of potash. In order to separate this gas from
the vapour of valyl evaporated with it, as well as from
carbonic acid, I passed it from the decomposing apparatus
through a system of tubes, (fig. i). d d is an empty tube
blown out to a bulb in the lower part, and surrounded
by a frigorific mixture. In this tube the larger quantity
of valyl vapour is condensed, a small portion which may
have escaped liquefaction being arrested in a Liebig's
apparatus g, filled with alcohol, the vapours of which
are condensed in a similar apparatus h containing water.
The two following bulbs k and / are filled with a solution
of potash, while the tube m contains potash in the solid
form, serving, both for the separation of carbonic acid,
and for the complete desiccation of the gas. Finally, to
obtain a perfect mixture, the evolved gases were col-
lected in the gas-holder B, which consists of a cylinder
of glass, 3 inches in diameter, and 1 1 inches in height,
containing an inverted bell-jar, open at the lower extremity,
Electrolysis of Organic Compounds. 31
and enclosing one vertical branch of each of the two
U-shaped tubes s and x. The bell-glass is fixed by a
holder in its lowest position, and the apparatus filled with
mercury to such an extent, that the two tubes through
which the air contained in the bell-jar is expelled, rise
only a few lines above its surface. The tube s, more-
over, at its horizontal extremity is connected by an air-
tight caoutchouc joint with the tube ;;/, while the branch
x communicates in the same manner with the delivery
tube r> which may be opened or closed at pleasure by
depressing or elevating it from the mercury of the trough ;
both the connectors being, moreover, furnished with
caoutchouc valves.
When the evolution of gases, occasioned by closing
the galvanic circuit in the decomposing apparatus, had
lasted nearly half an hour without interruption, and all
the air contained in its different parts had evidently been
expelled, the caoutchouc valve v was closely tied, while
the holder with which the bell-jar had been depressed in
the mercury, was gradually elevated as the vessel became
filled with the gas generated by the decomposition.
When a sufficient quantity of gas had been collected
in this manner, the evolution was interrupted by breaking
contact. By now tying the valve p t the gases contained
in the gas-holder were no longer in connexion with the
generating apparatus. By opening the valve v, and
depressing the bell Jar, the quantity of gas required could
easily be collected over mercury, and then transferred
into the eudiometer, or into the glass balloon, for the
determination of its specific gravity.
In determining the specific gravity, the following
numbers were obtained :
Vol. of gas in bal-
loon . . . 15 C. 755-9 mm 86.4 c.c.
32 Kolbe.
Weight of balloon
filled with gas . 15 C 771.0" 61.628 grm.
Weight of balloon
filled with air . 15 771.0,, 61.672
From the above numbers, the specific gravity is cal-
culated as 0.604.
In performing the eudiometrical analysis, I availed
myself of the circumstance of the odorous constituent
being absorbed by sulphuric acid. I therefore intro-
duced into a measured volume of the gas a coke ball,
saturated with strong fuming acid ; the sulphurous acid,
together with the sulphuric vapours, being subsequently
removed by a moistened ball of potash.
In this manner, the following numbers were obtained :
I.
Height of Corrected
Vol. r,- p mercury above vol.
observed. leni P" 1>ar ' level in the o'C. i">.
trough. Press.
Original vol.
(dry) 117.7 9-9 765.9""" 65.o imn 79.6
After absorp-
tion with sul-
phuric acid , 88.8 9.0 761.1,, 93.3 57.4
and potash
(dry)
The quantity of odorous substance in the mixed gases
absorbable by sulphuric acid, consequently amounts to
27.8 per cent.
The residual gas, no longer possessing any odour, and
burning with a pale blue, non-luminous flame, was trans-
ferred into a eudiometer furnished with platinum wires,
and exploded with oxygen, when it was found to consist
of pure hydrogen.
Another portion of the above mixture, when exploded
with oxygen, gave the following results :
Electrolysis of Organic Compounds. 33
II.
Height of Corrected
Vol. . v ,, mercury above Vol.
observed. lenip ' Han level in the o e C. i
trough. Press.
Original vol. 1 8 , ,.0759.4- 353., 42 . 4
(moist). /
After admis- \
sionof oxygen - 324.6 n.i 759.3,, 141-9 l8 9-5
(moist). j
After com- \
bustion L 222.7 1 1. 1 759.0,, 242.3,, 108.4
(moist). J
After absorp- j
tion of CO., [ 146.0 13.0759.1,, 318.2,, 61.4
(dry). "I
The gas remaining after the absorption of carbonic
acid consisted only of pure oxygen, as had been ascer-
tained in a previous experiment.
The above analysis leads to the following results :
Volume of com- Oxygen Carbonic acid
bustible gas. cons d . prod d .
42.4 85-7 "' 47-0
or
100.0 * . 202.1 . . 1 10.8
The mixture of gases under investigation containing,
according to experiment II, 72.2 per cent, of hydrogen,
requires 36. i vol. of oxygen for its combustion ; it is
therefore evident that the remaining 27.8 vol. require
166 ( = 202.1 36.1) vol. of oxygen, in order to produce
1 1 0.8 vol. of carbonic acid. These numbers stand very
nearly as, 1:6:4, or, in other words, i volume of the
odorous gas requires 6 vol. of oxygen to produce 4 vol.
of carbonic acid. Four vol. of carbonic acid consisting,
however, of 2 vol. of carbon and 4 vol. of oxygen, and
altogether 6 vol. of oxygen having disappeared, 2 vol.
having evidently served for the combustion of 4 vol. of
c
34 Kolbe.
hydrogen, it is obvious that the odorous gas contains 2
vol. of carbon and 4 vol. of hydrogen condensed into one
volume; hence its specific gravity is, 1.934.
2 vol. of Carbon vapour > ' ; ;. . 1.658
4 Hydrogen ' ; ^ j "< . 0.276
i ., C 4 H 4 . . 1.934
According to the above experiment, the specific gravity
of a mixture of 72.2 vol. of hydrogen, and 27.8vol. of
the carbo-hydrogen, is equal to 0.604 ; hence it follows
that the specific gravity of the latter alone is, 1.993,
closely coinciding with the result of experiment.
The odorous carbo-hydrogen evolved at the positive
pole in the electrolytical decomposition of valerianate of
potash, according to these experiments, exhibits the com-
position of olefiant gas, but possesses a specific gravity
double that of this compound. In this respect, it agrees
with the carbo-hydrogen discovered by Faraday, and
named by Berzelius diteiryl, with which it, in fact,
appears identical by its comportment with chlorine.
If the mixed gases, washed with potash and alcohol,
and collected in the gas-holder, be passed through a
chloride of calcium tube into a flask (provided with three
tubulures, one of which terminates in a narrow aperture),
and mixed with perfectly dry chlorine, an excess being
carefully excluded and light as much as possible avoided,
the sides of the flask become quickly covered with oily
drops, which soon collect into larger globules, and flow
out from the lower aperture, while hydrochloric acid,
formed by the direct combination of chlorine with the
free hydrogen, is disengaged. During the whole process
a slight evolution of heat is perceptible.
About half an ounce of the oily liquid, which had
been collected in the vessel placed under the lower
aperture of the flask, was first treated with slightly alka-
Electrolysis of Organic Compounds. 35
line, and afterwards with pure water, in order to separate
dissolved hydrochloric acid ; and it was then dried over
fused chloride of calcium, and subjected to a fractional
distillation. The portion which boiled between i25C.
(257 F.) and 130 C. (266 F.) forming by far the larger
quantity, was separately collected and purified by re-
peated rectifications, when a nearly constant boiling-
point at 123 C. (253.4 F.) was obtained.
This compound possesses the following properties.
It is a clear colourless etherial liquid, insoluble in and
heavier than water. It has an agreeable sweetish odour
and taste, deceptively similar to that of Dutch liquid. It
dissolves with facility in alcohol and ether, and boils at
the constant temperature of i23C. (253.4 F.) ; mixed
with alcohol it burns with a luminous smoky flame, with
evolution of hydrochloric acid. Its specific gravity at
18 C. (64.4 F.) is 1. 1 1 2, the density of its vapour 4.426,
the latter being calculated from the following data :
Substance employed . . . 0.244 grm.
Vol. of vapour observed . . 67.7 c. c.
Temperature . . ' . . i39.oC.
Bar. pressure . V "'... . 751.0 mm.
Col. of mercury to be deducted 51.0 ,,
Pressure of oil col. at 17 C. . 366.0 ,,
By combustion with protoxide of copper the following
results were obtained :
I. 0.3990 grm. of substance gave :
-559o ,, carbonic acid, and
0.2470 ,, water.
II. 0.2165 ,, ., passed over ignited lime, dis-
solved in nitric acid and
precipitated with nitrate of
silver gave :
0.4790 ,, ,, chloride of silver.
36 Kolbe.
These numbers coincide with the formula :
C 4 H 4 Cl, or C 8 H 8 C1 2 .
Theory. Experiment.
8 equiv. of Carbon . ( ,-. ., 600.0 37.8 38.2
8 ,, Hydrogen . 1000 6.3 6.8
2 ,, Chlorine .. 886.0 55.9 55.5
1586.0 100.0 100.5
If we adopt, in this compound, a similar condensation
of the elements, as in the oil of olefiant gas, the specific
gravity of its vapour should be, 4.3837.
2 vol. of Carbon . ; L ! ' : ' 1.6584
4 Hydrogen ';" : \ 0.2764
i ,, ,, Chlorine i^fnr.nr. 1 : 2.4489
i the new Chloride . 4.3837
(with this number the result of experiment 4.426 closely
coincides).
It would have been extremely interesting to have
studied the comportment of this compound with an
alcoholic solution of potash, since its analogy to chloride
of elayl justifies the expectation that, in this case, chloride
of potassium, and a compound corresponding to chloride
of acetyl would have been formed, the latter being repre-
sented by the formula :
C fH
H ci
The small quantity of liquid at my disposal, unfor-
tunately, did not allow me to pursue the subject any
further. I must therefore confine myself to mentioning,
that on heating an alcoholic solution of the compound
with potash, a copious crystalline precipitate of chloride
of potassium was formed, while the characteristic odour
Electrolysis of Organic Compounds. 37
of the compound was replaced by that of a very volatile
liquid, having probably the formula :
C ^
c Hd/>
which remaining dissolved in the alcoholic solution, was
precipitated, on the addition of water, in small drops,
which separating at the sides of the vessel, united only
with difficulty ; the liquid remaining milky for a con-
siderable period.
By the action of chlorine, on the above carbo-hydrogen,
with the fluid boiling at 123 C. (253. 4 F.), higher chlo-
rinated products are formed, even when an excess of
chlorine has been carefully avoided. The slow elevation
of the boiling-point from 123 C. (253. 4 F.) to 160 C.
(320 F.), at once intimates that we have, in this case,
other substances richer in chlorine, which possibly might
have been separated by fractional distillation of a larger
quantity.
The combustion of 0.3620 grm. of the product, dis-
tilling at 132 C. (269. 6 F.), gave 0.4600 grm. of carbonic
acid, and 0.1800 grm. water, corresponding to the follow-
ing per-centage composition :
Carbon ... ,'. . 34-6
Hydrogen . . 5.5
A compound still richer in chlorine is obtained by
passing the gas through pentachloride of antimony, and
distilling the substance thus produced. During the pro-
cess of absorption, the mixture blackened, with the evo-
lution of hydrochloric acid. The oily product obtained
was purified by repeated distillation with water, dried
over chloride of calcium, and subjected to analysis, when
it exhibited the following per centage composition :
Carbon . . 28.4
Hydrogen . . 4.0
Chlorine 68.2
38 Kolbe.
being evidently a mixture of different chlorinated com-
pounds, whose composition may be represented by the
general formula :
Cs H (S _ X) Cl ( 2+*)
The opinions of chemists regarding the rational com-
position of the oil of olefiant gas, are, as is well known,
still divided, as to whether it should be considered as
the chlorine compound of a radical C 2 H 2 , or whether its
atomic weight should be doubled, in which case it would
appear as the hydrochlorate of chloride of acetyl.
C 4 (f}, H Cl.
This question must remain undecided as long as both
views can still claim arguments of equal force. Now,
whichever of these opinions may in future be found
correct, it will evidently determine our views respecting
the chemical constitution of the above chlorinated oil
produced from ditetryl, or, in other words, it will decide
whether we have to adopt the formula :
C 4 H 4 Cl, or CJ^I H Cl,
as the true exponent of its rational composition. This
supposition once recognised will add new force in favour
of the latter mode of representation, if we bring to bear
upon this case the law of Kopp respecting the regularity
displayed in the boiling points of homologous liquids,
(to employ an expression lately introduced to designate
the members of such series of bodies), which, like the
alcohols or the fatty acids, are represented as being
derived from a starting member by the addition of n
times C 2 H 2 , C 4 H 2 , on any other carbo-hydrogen, ex-
periment having (within certain limits) evinced the fact
that the boiling points of homologous fluids rise 19 C.
(34 F.) for each additional equivalent of the' carbo-
Electrolysis of Organic Compounds. 39
hydrogen C 2 H 2 . The chloride of ditetryl, C 4 H 4 Cl,
which boils at 85 C. (185 F.), differing from chloride
of elayl by one equivalent of the carbo-hydrogen C 2 H 2 ,
should boil at 104 C. (2 19. 2 F.) ; on doubling, however,
the atomic weight of the two bodies, (chloride of elayl
C 4 H 4 C1. 2 , and chloride of ditetryl C s H 8 C1. 2 ), their
elementary difference becoming equal to 2 (C, H 2 ), the
boiling point of the latter should be 123 C. (253.4 F.),
which is the temperature actually observed by experiment.
Although this observation cannot- be considered as a
direct argument for the assumed molecular arrangement,
I consider it nevertheless of sufficient w r eight to assist in
the ultimate decision of the question regarding the atomic
constitution of the two compounds.
We find no difficulty in explaining the formation of
the carbo-hydrogen C 4 H 4 , or C 8 H s , from valerianic
acid ; like the valerianate of the oxide of valyl, it is
evidently a secondary product of the decomposition of
valyl, and most probably formed by the action of the
oxygen separating along with valyl, at the positive pole.
We may assume that, under the influence of this oxygen,
valyl is deprived of one equivalent of hydrogen, yielding
one equivalent of ditetryl and one equivalent of water.
The action of electrolized oxygen, on a solution of
valerianate of potash, therefore gives rise to three distinct
phenomena :
i st. A decomposition of the acid into valyl and car-
bonic acid :
HO, (C 8 H 9 ) C 2 O 3 + O = C 8 H 9 + 2 CO, + HO.
Valerianic acid. Valyl.
2ndly. The decomposition of valyl into ditetryl and
water :
Valyl. Ditetryl.
40 Kolbe.
3rdly. A direct oxidation of valyl into oxide of valyl,
which combines in the nascent state with free valerianic
acid.
C^Hc, + O + (C 8 H ) C, O, = C 8 H O, (C 8 H 9 ) C, 3 .
Valyl. Valerianic acid. Valerianate of oxide of valyl.
The two latter processes appear to take place simul-
taneously, though perfectly independent of each other.
I have not, however, succeeded in exactly ascertaining
the circumstances which favour the formation of the one
or the other.
ELECTROLYSIS OF ACETIC ACID.
The remarkable analogy of the series of acids
(C 2 H 2 ) n + O 4 , induced me to believe that acetic acid
would undergo a similar decomposition to valerianic
acid, yielding, by absorption of one equivalent of oxygen,
methyl and carbonic acid :
HO (C 2 H 8 ) C> O 3 + O = Q H 3 + 2 CO, + HO.
Acetic acid. Methyl.
In a preliminary experiment, it was found that on de-
composing a concentrated solution of acetate of potash,
gaseous products only were evolved, consisting of car-
bonic acid, hydrogen, a combustible inodorous gas, and
a compound possessing a peculiar etherial odour, and
absorbable by sulphuric acid. In the investigation of
these gaseous products, I availed myself of the same
decomposing apparatus as was employed in the decom-
position of valerianic acid ; the evolved gases were first
passed through a series of bulb tubes containing potash,
afterwards through a tube filled with sulphuric acid (for
the absorption of the odorous gas), and finally made to
pass through a tube containing pieces of fused hydrate
of potash, previous to collection in a gas-holder. In this
Electrolysis of Organic Compounds. 41
operation it is necessary to employ a very concentrated
solution of the potash salt perfectly free from chloride of
potassium, the smallest trace of the latter giving rise to
the formation of chloride of methyl, which is easily
recognisable by the green-bordered flame with which it
burns when inflamed in contact with the air.*
When the evolution of gas had continued for about an
hour, and had entirely displaced all traces of atmospheric
air contained in the system of tubes and the gasometer,
I filled the latter by gradually raising the bell, the delivery
tube dipping under the mercury. The apparatus being
too small to allow a sufficient quantity of gas being col-
lected for taking its specific gravity, for eudiometrical
analysis, and for combustion with protoxide of copper,
the bell-jar was again fixed before being completely filled,
and the gas issuing from the tube r was collected in a
flask, for the determination of the specific gravity.
The contents of the gasometer were now easily con-
fined by tying the caoutchouc valves p and v over the
inserted glass rods, after the collection of gas had ceased
from the interruption of the galvanic current.
In determining the relative proportion of carbon and
hydrogen, an ordinary combustion-tube, open at both
ends, was employed ; when filled with freshly ignited
protoxide of copper, the anterior extremity was connected
with the usual potash bulbs and chloride of calcium
tube, the posterior end being attached by a caoutchouc
tube to the gasometer. After opening the caoutchouc
valve 27, the silken cord was untied, and by gently de-
* In a similar manner various other secondary products are formed,
a mixture of valerianate of potash and chloride of potassium, for
example, produces in the place of valyl, a chlorinated, etherial com-
pound ; a disagreeably smelling compound is- obtained by exposing
a mixture of acetate of potash and sulphide of potassium to the
action of a galvanic current, the anode being formed of a platinum
plate.
42 Kolbe.
pressing the bell-jar, a continuous stream of gas passed
over the ignited protoxide of copper, until a sufficiency
of carbonic acid and water had been collected, when the
caoutchouc valve was again closed. The posterior tube
connected with the gas-holder was now cut, in order to
allow of the removal of the carbonic acid remaining in
the apparatus.
The following are the numbers obtained :
Carbonic acid . $JKi 0.2470
Water . . . 0.2635
corresponding to a ratio of i equivalent of carbon to 2.06
equivs. of hydrogen, or of i volume of carbon vapour to
5.2 vols. of hydrogen.
The specific gravity of the gas collected in a small
flask over mercury was found to be 0.403.
Temp. Pressure.
Volume of gases in flask i9-3C. 749. 2 mm 211.3 cc -
Mercury column to be de-
ducted . . . ... 15.0 ,,
Weight of flask filled with
gas .... 22.oC. 749.0 46.669 grm.
Weight of flask filled with
air . . . . 46.819
The further data for the composition of the gas were
obtained by eudiometrical analysis, which exhibited the
presence of a minute quantity of oxygen.
Height of Corrected
Observed. Temp. Bar. mercury vol. o C. and
C J . column. i 111 pressure.
Volume of gasl
employed ^37-3 J 9-3 747-2 nim 3i-5 mm 8 9- 6
(moist).
After absorp- I
tion of oxygen j- 1 3 2.0 19.0 740.0,, 35.9,, 86.9
(moist).
Electrolysis of Organic Compounds. 43
The quantity of oxygen, therefore, amounts to 3 per
cent. The residuary gas was transferred into a larger
audiometer, and detonated with oxygen in experiments
II a and II b, the following numbers were obtained :
II a.
m, ,--/. i T^m, Height of Corrected
Observed Temp. BarQm mercury vol.o'C.and
column. i"> pressure.
Volume of gasl
employed [200.0 18.0 749.0'""' 373.4""" 67.6
(moist). J
After admis- 1
sion of oxygen [47 5. 9 17.4751.2,, 92.3,, 287.6
(moist). J
After combus- 1 , , ,
tion (moist). J3.6 18.0 751-1 225.6,, 165.4
After absorp- \
tionof carbonic [283. 2 17.7 748.8,, 288.6,, 122.3
acid (dry). J
After admis- \
sion of hydro- [574.5 17.8747.5,, 6.0,, 399.0
gen (dry). J
After combus- 1
tion (moist). ) 114 ' 2 '7- 4 748. 9 460.2,, 29.4
Volume of gasl
employed - 91.8 18.9 740.2 476.3 21.26
(moist). J
After admis- \
sion of oxygen [410.2 19.0740.3,, 153.7,, 218.7
(moist). J
After combus- 1 ,,
tion (moist). P 66 - 2 19-0740.4,, i97-i 180.43
After absorp- \
tion of carbonic [341.4 18.0 744.0,, 222.1,, 167.15
acid (dry). J
44 Kolbe.
Vol. of gases Oxygen Carbonic acid
used. consumed, generated.
Experiment II a . 67.6 97.7 43.1
Experiment II b v 21.26 30.3 13.3
In calculating these numbers for a mixture of hydrogen
and methyl, we find that in both experiments a smaller
quantity of oxygen has disappeared than is required for
the perfect combustion of such a mixture.
This circumstance appears to point out the presence of
oxide of methyl, which accompanies methyl itself in pretty
constant proportion. In designating the quantity of
combustible gas employed by A, the oxygen which has
disappeared by B> the carbonic acid produced in com-
bustion by C; and further, the quantity of oxygen, methyl,
and of oxide of methyl, respectively by x, j, and z, we
arrive at the following equation,
by which we obtain for x, y, and 0, the following values :
2 A C
X =
2
y _ 4 B 2A 5 C
26.
If we now substitute for A, B, and C, the numerical
values found, we arrive at the following composition for
the two consumed volumes of gas (Exp. II a and II b) :
Experiment II a. Experiment II b.
Hydrogen . . . 46.1 14.60
Methyl . . . 20.0 6.10
Oxide of methyl . . 1.5 0.56
Total volume^ ". 67.6 21.26
Electrolysis of Organic Compounds. 45
Hence, from experiments I. and II. , results the following
per-centage composition of the mixed gases :
Oxygen. < ^ 3.0 3.0
Hydrogen . . . 66.0 66.6
Methyl . ! ' M / ; "\ 28.8 27.8
Oxide of methyl i 2.2 2.6
100.0 100.0
The specific gravity of a gaseous mixture of this com-
position would be 0.4123 which closely coincides with
the numbers found by experiment, 0.403. This com-
position receives further confirmation from the relative
proportions of carbon and hydrogen, obtained by com-
bustion with protoxide of copper.
Carbon vapour. Hydrogen.
28.8 vol. Methyl contain 28.8 vol. 86.4 vol.
2.2 Oxide methyl 2.2 ,, 6.6 ,,
66.0 Hydrogen 66.0
The gaseous mixture . 31.0 159-
Being the ratio of 31.0 vol. of carbon vapour to 159.0
vol. of hydrogen, or of i vol. of carbon vapour to 5.13
vol. of hydrogen, very closely coinciding with the above
experimental ratio of i : 5.21.
I have before mentioned, that the gases evolved in the
electrolysis of acetic acid, contain a gas which is absorb-
able by sulphuric acid. Independently of the remarkable
odour of acetate of methyl which this gas possesses, the
supposition that acetate of methyl is actually obtained
among the products of the decomposition of acetic acid,
receives some support from the analogous decomposition
of valerianic acid. With the view of ascertaining the
46 Kolbe.
per-centage of this body in the mixture of gases, and to
study its nature, I repeated the above experiments with
a portion of gas which had not previously been passed
through sulphuric acid, and which consequently still
contained the odorous principle ; it burned like the
other, with a feebly luminous, bluish flame.
An indefinite volume being passed from the gas-holder
over ignited protoxide of copper, gave :
0.249 g rm - f carbonic acid, and
0.247 water.
Corresponding to the ratio of :
i vol. of carbon vapour, and
4.851 vols. of hydrogen.
The specific gravity of the mixture was found to be
0.4373, as is seen by the following experiment :
Te P' Pressure.
Volume of gas in flask . 18.0 74 i.o mm 211.7 cc.
Weight of flask filled with
gas .... 19.0 749.0,, 42.4065 grm.
Weight of flask filled with
air . . . * 4 2 -55
To ascertain the per-centage of free oxygen and of the
odorous constituent, I first determined, in a measured
volume, (experiment III), the quantity of the latter by
absorption with a coke ball saturated with sulphuric acid,
and subsequently the amount of oxygen, by introducing
a ball of phosphorus. The remaining portion of com-
bustible gas was then detonated with oxygen in a large
eudiometer, (experiment IV T ).
Electrolysis of Organic Compounds. 47
III.
Observed Temp. ,,_ Hejgtof V**^
column. ii pressure.
Volume of gasl f
used (moist). I" 6 ' 4 I? ' 8 74 ?' 2 2I ' 2 "' 6 7
After absorp- ^
tion with sul-
phuric acid ["3- 8 '7-9 6 ' 4-8 77-3
(dry).
After absorp- ^
tion of oxygen -113.0 17.6746.0,, '25.1,, 76.5
(dry).
IV.
Volume of gas
free from
oxygen and ^190.6 17.8746.0,, 378.2,, 63.1
odorous con-
stituent (moist).
After ad mis- 1
sion of oxygen [373.9 17.9744.7,, 192.4,, 188.4
(moist).
After combus- 1 n /-
tion (moist). J 2 8 - 6 I8 ' 743 -8,, 339-6,, 72.17
After absorp- 1
tion of carbonic [105. 3 18.2 745.9,, 465.7,, 27.66
acid (dry). J
After admis- "j
sionof hydro- [311.5 18.0750.6,, 255.7,, 144.63
gen (dry). J
After combus- V o *
tion (dry). j l82 ' 6 l8 - J 75O-6 386.5,, 62.35
According to the latter experiment, it follows that 63.1
vols. of gas previously treated with sulphuric acid and
4 8
Kolbe.
phosphorus, require for combustion 97.4 volumes of
oxygen, giving rise to the formation of 44.51 vols. of
carbonic acid. If we now calculate these numbers
according to the above equation for hydrogen, methyl,
and oxide of methyl, we find that the original 63.1 vols.
contained 40.85 vols. of hydrogen, 20.9 vols. of methyl,
and 1.35 vol. of oxide of methyl. From these data, and
likewise from the results of experiment III, we obtain
the following per-centage composition of the mixture, in
which the gas absorbable by sulphuric acid is enumerated
as acetate of methyl.
Oxygen . ' r
Hydrogen .\
Methyl .
Oxide of methyl
Acetate of methyl
0.7
63.8
32.6
2.1
0.8
100.0
The specific gravity of such a mixture should be
0.4430, which does not far differ from experimental
results, the number obtained being 0.4370.
Oxygen
Hydrogen .
Methyl
Oxide of methyl .
Acetate of methyl
Volume
per-cent.
0.7 X
63.8 x
32.6 x
2.1 X
0.8 x
Specific
gravity.
1.1092
0.0691
'0365
i-5 8 93
Weight.
0.7647
4.4086
Q-443
If we calculate the relative volumes of carbon and
Electrolysis of Organic Compounds. 49
hydrogen contained in this mixture of gases, we obtain
the following numbers :
Hydrogen -
63.8 vol. H containing 63.8 vol.
32.6 C 2 H 3 '";,' . 3 2 - 6 vo1 - 97- 8
2.1 C 2 H 3 O _ J3 ,f 2.1 , ' 6.3
0.8 C 2 H 3 O, A 1.2 ';,"' 2.4
Being a proportion of 'V J 35.9 to 170.3
or of one volume of carbon vapour to 4.74 vols. of
hydrogen, which coincides with the results obtained by
combustion with protoxide of copper, viz.: i vol. of car-
bon vapour to 4.85 vol. of hydrogen. The per-centage
composition gains additional support by the eudiometrical
analysis of the same gas, which still contained the odorous
principle, but which was previously freed from oxygen.
The following numbers were obtained :
OWrvpd TVmn Height of Corrected
Observed lemp. BarQm mercu ry vol. o C. and
column. im pressure.
' 38 ' * 7S-.5- .-i- 39-
After admis- \
sion of oxygen U60.6 18.3 750.2., 206.4,, I 7 8 -5
(moist).
After combus- ) , ,
tion (moist). ) 26 3'9 l8 - 2 75. i 33.9 106.8
After absorp- \
tion of carbonic U 1 3.9 18.2 748.4,, 354.0,, 78.9
acid (dry). J
In the combustion of 39.1 vols. of this gas 60.5 vols.
of oxygen are consumed, giving rise to the formation of
D
50 Kolbe.
27.9 vols. of carbonic acid. By now calculating the
quantity of oxygen necessary for the combustion of 63.8
vols. of hydrogen, 32.6 vols. of methyl, 2.1 vols. of oxide
of methyl, and 0.8 vol. of acetate of methyl, and likewise
taking into consideration the amount of carbonic acid
produced, we arrive at results but slightly differing from
the numbers obtained by experiment :
., , Oxygen Carbonic
Vols - vols. acid vols.
63.8 H requiring for combustion 31.9 and producing
32.6 C 2 H 3 114-1 , 65.2
2.iC 2 H 3 O_ ,, 6.3 4.2
0.8 C 2 H 3 O, A 2.8 2.4
99.3 mixed gases 155.1 71-8
or that 39.1 vols. require for combustion 61.0 vols. of
oxygen (experimental result, 60.5 vols.), producing 28.2
vols. of carbonic acid (experimental result, 27.9).
These facts sufficiently prove that the quantity of the
compound imparting the peculiar etherial odour to the
gases, which are evolved in the electrolytical decomposi-
tion of acetate of potash, is so small, that if, as experiment
seems to point out, it actually consists of acetate of methyl,
it becomes almost impossible to condense it by a low
temperature. An experiment made with this view was,
indeed, perfectly unsuccessful. The ready absorption of
this body, by sulphuric acid, agrees with the comport-
ment of acetate of methyl ; the acid employed in the
experiment assumed a yellowish tint, and darkened on
the application of heat, with the evolution of acetic and
sulphurous acid vapours.
The above experiments had been completed, when I
became aware that a gaseous mixture, consisting of one-
third methyl and two-thirds of hydrogen, possesses the
same specific gravity as is exhibited by a mixture of two-
Electrolysis of Organic Compounds. 51
thirds of marsh-gas, and one-third of hydrogen, and
moreover, both mixtures contain the same relative amounts
of carbon and hydrogen, and consequently consume, not
only an equal volume of oxygen in their combustion, but
produce the same quantity of carbonic acid ; and hence
the facts observed in the electrolysis of acetic acid might
lead to the assumption, that the gases evolved in its
electrolytical decomposition consist of hydrogen and
marsh-gas. With the view of removing all doubt on this
point, I have endeavoured to prepare methyl in a state
of purity : I availed myself for this purpose y of the de-
composing apparatus already described, which allows us
to collect with facility the products liberated at either
pole.
The interior cell containing the platinum plate was
closed for this purpose with the cork, which besides the
platinum wire for producing contact, contained, moreover,
the delivery tube through which the generated gases were
evolved, in order to be conducted through two bulb-tubes
filled with concentrated solution of potash, and afterwards
through a similar vessel containing sulphuric acid (for
the absorption of water and acetate of oxide of methyl)
and subsequently collected in the gas-holder. After
every trace of atmospheric air had been expelled, the
collected gas contained, nevertheless, a small quantity of
carbonic acid, the two potash bulbs not having been
sufficient to absorb the carbonic acid, which had been
evolved from the separated cell in much larger proportion
than in the former arrangement, because, in the former
experiment, the simultaneous liberation of acetic acid at
the positive pole effectually prevented the formation of a
carbonate.
The eudiometrical analysis of the mixture which, as
special experiment had proved, did not contain free
oxygen, gave the following results :
52 Kolbe.
VI.
OW.v-H T>m, Height of Corrected
Observed Temp. Barom> mer cury vol. o C. and
column. in pressure.
After absorp- ^
tion of carbonic V 90.9 17.2 744.8,, 44.9,, 59-86
acid (dry), j
VII.
>I 17.5 744.9 mm 457.4 mm 29.23
(moist).
After admis- 1
sion of oxygen Us 2.0 17.5 745.2 115.7,, 261.1
(moist). J
374.o.,.6,4S..,,.9..S,, '88-9
After absorp- 1
tionof carbonic [293.5 J7-5 746.0 273.6,, 130.5
acid (dry). J
According to these observations the gaseous mixture
contains 26.0 of carbonic acid, and 74.0 of combustible
gas, of which (experiment VII) 29.23 vols. require 101.37
vols. of oxygen for complete combustion, producing 58.4
vols. of carbonic acid, which closely corresponds with
the ratio, i : 3^ : 2 ; hence it appears that the gas evolved
with carbonic acid, at the positive pole, is actually methyl,
containing not even a trace of marsh-gas, which requires
the double volume of oxygen for its complete combus-
tion, and produces only an equal volume of carbonic
acid.
Electrolysis of Organic Compounds. 53
The experimental numbers correspond with the follow-
ing per-centage :
Carbonic acid . . 26.0
Methyl . . . ; 69.3
Oxide of methyl . . 4.7
IOO.O
The specific gravity of such a mixture is 1.188, a
number closely coinciding with the result of experiment,
which gave 1.172, as the following data will shew :
Temp. Barometer.
Volume of gas in flask !7-3* 7 J 7-6 212 c.c.
Weight of flask filled with gas 17.2 738.6 53.826 grm.
>, air 53-796
The gas remaining after the absorption of carbonic
acid (experiment VI), which is methyl mixed with traces
of oxide of methyl, possesses the following properties : it
is inodorous * and tasteless, insoluble in water, and burns
with a bluish non-luminous flame ; alcohol dissolves an
equal volume, absorbing it without residue ; neither sul-
phuric acid nor pentachloride of antimony dissolve it,
and hence it corresponds, in all its properties, to the
gas obtained from cyanide of ethyl, f
Methyl may be distinguished from marsh-gas, to which
it is in some respects very similar, both by its solubility
in alcohol, and its comportment with an excess of chlorine
gas, by which methyl is converted into sesquichloride
of carbon, while marsh-gas is transformed into the bi-
chloride.
In conclusion, I may observe, that on employing two
* The feebly etherial odour of the gas prepared from cyanide of
ethyl evidently arises from traces of cyanide of ethyl,
t Ann. der Chem. und Pharm. Bd. LXV. S. 269.
54 Kolbe.
decomposing cells, the gas evolved at the positive pole
does not contain carbonic acid, but consists of pure
hydrogen.
According to the observations I have communicated,
acetic acid, when decomposed in the circuit of the voltaic
current, is decomposed into methyl and carbonic acid,
both being liberated at the positive pole, whilst at the
negative pole, pure hydrogen only is evolved. It further
appears, that a small quantity of methyl is converted into
the oxide. On leaving out of consideration the small
quantity of the latter, one equivalent of acetic acid should
accordingly yield 2 vols. of hydrogen, 2 vols. of methyl,
and 4 vols. of carbonic acid, as is shown in the following
equation :
f H 2 vols.
HO, (C, H 3 ) C 2 O 3 = \ C 9 H 3 2 vols.
[2 C O 2 4 vols.
The gases evolved from the decomposing cell, in the
decomposition of acetate of potash, should therefore
consist of equal volumes of methyl and hydrogen ; as,
however, experiments II, IV, and V, show that nearly
double the amount of hydrogen is evolved, without an
equivalent proportion of oxygen being liberated, we are
led to the conclusion, that together with the above-
mentioned transformations a simultaneous decomposition
of water takes place, whose oxygen (considerably sur-
passing the amount contained in the oxide of methyl)
evidently oxidizes a portion of the liberated methyl com-
pletely into carbonic acid and water : from this fact,
however, it would follow, that carbonic acid would be
produced in much larger proportion compared with
methyl, than is indicated by the foregoing formula. With
the view of deciding this question, I have investigated
the mixture of carbonic acid and methyl, evolved at the
Electrolysis of Organic Compounds. 55
positive pole, which had been previously freed from acetic
vapours which might have been carried over, by passing
the gas through a bulb-tube containing water.
VIII.
After absorp- \
tion of carbonic V 35.3 15.8753.3,, 99- 2I -9 6
acid (dry). J
The gaseous mixture under investigation was found to
contain 21.96 vols. of methyl and 51.31 vols. of carbonic
acid ; or, in other words, for every volume of the former,
there are 2\ volumes of the latter, instead of 2 volumes,
as indicated by the above equation.
These observations appear sufficient to prove, that in
the electrolysis of acetic acid, even when employed in the
form of a concentrated solution of its potash salt, a
simultaneous decomposition of water takes place, which
may perhaps be partially or entirely avoided by modifying
the electrical current.
ON THE ELECTROLYSIS OF ACETIC
ACID.*
HAVING twenty years ago resolved acetic acid into
carbonic acid and methyl, by the electrolysis of
the aqueous solution of its potassium salt, I further
examined the behaviour of free acetic acid towards
* [From The Journal of the Chemical Society of London, Vol. 21
(1868), pp. 195-196.]
56 Kolbe.
oxygen evolved by electrolysis, in the hope of thereby
oxidising it to glycollic or dioxyacetic acid.
I have lately resumed these experiments, using as the
electrolyte, glacial acetic acid, mixed with just enough
water and sulphuric acid to render it capable of conduct-
ing the galvanic current. For electrodes, I used two
platinum plates, which were immersed in the liquid
without any separating diaphragm, and the liquid was
kept cool during the electrolysis.
If, after the action of the current has been continued
for twelve hours, the liquid be freed from sulphuric acid
by baryta-water, and then evaporated, there remains a
small quantity of a viscid non-volatile substance, which
exhibits strong acid properties, and crystallises slowly
over oil of vitriol.
My expectation that this acid might be glycollic acid
has not been realised; Its behaviour, and more especi-
ally the properties of its salts, are quite distinct from those
of glycollic acid, and yet its calcium salt has exactly the
composition of glycollate of calcium.
The quantity of this acid obtained being always very
small, I have not hitherto been able to analyse any of its
other salts.
If the further investigation of this interesting acid
should establish its isomerism with glycollic acid, the
result might, perhaps, tend to support the assumption
that the four hydrogen atoms of marsh gas, or the three
hydrogen atoms of methyl, are not of equal value.
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