Page images
PDF
EPUB

3. Oxalic acid.—My former analytical experiments on the oxalate of lead, indicate 25•2 of oxalic acid in 100 of oxalate of lead. The analysis was made by combustion, but without attending to the lead which was reduced and concealed in the oxide of lead obtained. Later experiments on four parts of oxalate of lead gave me a loss amounting to 0.9835; the oxide being dissolved in vinegar, 0·095 of metallic lead remained. This indicates 0·009 of oxygen, which must be subtracted from the loss in order to obtain the true quantity of acid; of course it amounted to 0.9816, or 24:54 per cent of the weight of the oxalate. This result was constant in various experiments. The oxalate of lead then is composed of Oxalic acid ....

24.54

100 Oxide of lead

75.46

30705

100.00

64.99 of oxygen.

But 30705 of oxalate of lead contain 22.062 of oxygen. And since according to my old experiments on oxalic acid, it contains three times as much oxygen as the base, it follows that it ought to contain 66.186 per cent.

I mentioned before that the analyses which I made by means of the brown oxide of lead gave me too little oxygen and too much hydrogen and carbon. The result of one of these experiments on oxalic acid was 0:66 per cent of hydrogen, 34:34 of carbon, and

In my repetitions by my new method, I burnt four parts of oxalate of lead with two parts of hyperoxymuriate of potash. The quantity of water produced weighed only 0:019; hence I suspected that this oxalate, which had been strongly heated, might have been partly decomposed. I therefore repeated the experiment with an oxalate that had been dried in a temperature below 2120 tained exactly the same result. I next suspected that I had taken too little hyperoxymuriate of potash, in consequence of which some empyreumatic oil might have been formed, though no trace of it appeared in the water. I therefore burnt two parts of oxalate of lead with two parts of of hyperoxymuriate. I obtained 0.004 of water in the receiver, and 0·001 in the tube with the muriate of lime. So that the result was almost exactly the same, giving 0:02 instead of 0.019 of water from four of oxalate. These four parts contain 0.9816 of oxalic acid; hence it follows, that this acid contains only 0.23, or 0.24 per cent. of hydrogen.

The carbonic acid produced weighed from 1.138 to 1•140, which makes 32.16 per cent. of carbon. A little of the carbonic acid remained, combined with the soda as in other experiments; but this quantity could not be determined, because a portion of the oxide of lead was converted into minium, and gave a red colour to The colour was the same when I endeavoured to

G

[ocr errors]

the burnt mass.

Vol. V, No II.

[ocr errors][ocr errors][ocr errors][ocr errors][ocr errors]

[FEE, keep the whole tube red hot during the combustion of the oxalate. Another portion of the oxide was changed into submuriate, as I satisfied myself by digesting the oxide in nitric acid, after it had been well washed. Oxymuriatic acid was disengaged, while at the same time neutral nitrate and muriate of lead were formed.

Though in consequence of this circumstance, it is impossible to determine the quantity of carbon with perfect precision, we know at least that it must contain more than 32:6, which would have been the result if all the oxide had been converted into minium, and less than 35 per cent., which would have been the result if no part of the oxide had been converted into minium. By attending to these two extremes, we find without difficulty, that the oxygen and carbon exist in such proportions in oxalic acid, that there is one volume of carbon for every li volume of oxygen, or two volumes of carbon for every three volumes of oxygen.

"To determine the composition of oxalic acid, we must then ascertain the relation between the volumes of its oxygen and hydrogen. This is difficult, because the quantity of hydrogen is so small, that analysis is not able to decide concerning it. I think, however, that we can find it from other circumstances. There can be no doubt that the composition of oxalic acid is such, that in the oxalates the hydrogen of the acid is combined with a certain number of entire volumes of the radicle of the base ; but saline bases

contain one, two, or three volumes of oxygen, without this producing any change in the ratio of the oxygen of the acid with that in the base. When we reflect on this, we perceive that with the known ratio between the carbon and oxygen in oxalic acid, there are only three modes of combination in which the above stated circumstance, that a volume of hydrogen in the acid is combined with a certain number of entire volumes of the radicle of the base,) can take place; namely, H + 2C + 30, or H + 12 C + 18 0, or H + 24 € + 36 7. For the degrees above this are not probable. The difference between these three degrees is so great, that the quantity of hydrogen found by experiment must be sufficiently exact to determine which of them belongs to oxalic acid. But analysis has given much more hydrogen than is consistent with the third of these, but less than would be requisite for the first mode of combination. But all the circumstances of the analysis agree perfectly with the idea, that oxalic acid is composed of one volume hydrogen, 12 volumes carbon, and 18 volumes oxygen. This constitures

[ocr errors][ocr errors]

may

[ocr errors][merged small][merged small]
[ocr errors]
[ocr errors]

per cent. :

serap

* In my memoir On the cause of Chemical Proportions, Annals of Philosophy, December, 1813, I have stated by a mistake in the calculation that ihis acid contains 27 volumes of carbon. It is obvious that this error is of no consequence relative to the subject treated of in that memoir. I acknowledge however that at present I do not lay much stress on that argument against the corpuscular doctrine. For it is clear that the compound atoms of organić nature ought to have a mechanical structure as different from that of inorganic atoms as their composition is different,

[merged small][merged small][ocr errors][merged small]
[ocr errors][ocr errors][merged small][ocr errors][merged small][merged small]

It follows from these reflections, that in an oxalate whose base contains only a single volume of oxygen, the hydrogen of the acid is combined with six volumes of the radicle of the base. When on the other side the base contains tivo volumes of oxygen, the hydrogen of the acid is combined with three volumes of ihe radicle of the base. When the base contains three volumes of oxygen, then the hydrogen is combined with two volumes of radicle. This may be seen in the following formulas, representing the oxalate of copper, the oxalate of lead, and the peroxalate of iron.

6 Cu O + H C12 0 18
3 PI 02 + H C12 (13

2 Fe 03 + HC12 018
Let us now examine the result of the analysis of this acid by
Gay-Lussac and Thenard. They employed in it oxalate of lime
dried in the temperature of boiling water. This oxalate in that
state contains water of combination, the quantity of which deter-
mined both by the experiments of Mr. Vogel of Bayreuth, and by
calculation, is such, that it contains a quantity of oxygen equal
to that in the lime; that is, very nearly. 12 per cent. Therefore
the oxalic acid used in their experiments consisted of 80 pure acid
+ 20 water. If we take away these 20 of water, that is to say, 2:35
hydrogen, and 17.75 oxygen, from the result af the analysis of
Gay-Lussac and Thenard, we have

Result of Gay-Lussac and Thenard. Do, corrected,
Hydrogen
2-745

0-493
Carbon
26.566

33.217
Oxygen
70-689

66•290

[ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small]
[blocks in formation]
[merged small][ocr errors][merged small]

This result agrees so well with my experiments, that it serves to confirm what I have advanced above. *

4. Succinic acid.-I purified succinic acid from the empyreu

[merged small][ocr errors]

* Dr. Thomson in the Philosophical Transactinns for 1807, has given an analysis
of oxalic acid made by dry distillation and the analysis of the products. He found
it composed of
Hydrogen

4
Carbon

32 Oxygen

64

ophy

COP Jendt

[ocr errors]

das

100 I am astonished that he could have come so near the truth potwithstanding the dificulties of the method which he follow eủ.

a

The

matic matter with which it is usually impregnated, in the following
manner. I sublimed it in a moderate heat, the product of the sub-
limation is succinic acid, contaminated with colourless oil of amber,
which becomes coloured by exposure to the air. I combined it with
carbonate of ammonia, adding a slight excess of the alkali. I
then digested it with charcoal, prepared by exposing coagulated
blood to a strong heat in a covered crucible. This charcoal ab-
sorbed the empyreumatic matters, and allowed the succinate of am-
monia to crystallize of a white colour. From this succinate of
ammonia, I prepared by the addition of nitrate of lead. with the
precautions already stated, pure succinate of lead. 100 parts of
this succinate analysed by combustion gave 69.1 of oxide of lead.
Hence the salt is composed of
Succinic acid...

30:9

100.00 Oxide of Lead..

69:1

223.62

[ocr errors]
[ocr errors]
[ocr errors][ocr errors][ocr errors]

100.0 But 223.62 of oxide of lead contain 16 of oxygen.

Subsuccinate of lead obtained by digesting the neutral succinate in ammonia, dried in a vacuum at the temperature of boiling water, and analyzed by combustion, yielded 86.93 per cent. of oxide of lead. A great excess of ammonia poured upon this subsuccinate did not alter it; for it gave afterwards the same analytical result. The subsuccinate of lead then is composed of Succinic acid

13.07

100 Oxide of lead

86.93

666

.....

[ocr errors]
[merged small][ocr errors][merged small][ocr errors]

100.00 But 223.64 X 3 = 670.8, which differs but little from 666. Hence it is evident, that the succinic acid in this salt is combined with three times as much base as in the neutral succinate. Of course succinic acid must contain three volumes of oxygen.

1.294 of succinate of lead, equivalent to 0.4 of succinic acid, produced by combustion 0·1536 of water, equivalent to 4.512 per cent. of hydrogen, and 0.656 of carbonic acid in form of gas, to which adding the 0·044 remaining in the soda, the whole amounts to 0.7, equivalent to 47.6 per cent. of carbon. The acid therefore is composed of Hydrogen

4:512 Carbon

47.600 Oxygen

47.888

[merged small][ocr errors]

100.000

[ocr errors]

But 16 x 3 = 48. Hence it follows, that the acid contains three volumes of oxygen. We find that the carbon and hydrogen amount each to four volumes; so that succinic acid is composed of 4 H + 4C + 30, which makes in a hundred parts

Hydrogen

4.218 Carbon

47.859 Oxygen

47.923

100 The true capacity of saturation of the acid then is 15.9743, instead of 16 given by experiment.

(To be continued.)

ARTICLE III.

A Memoir on Iodine. By M. Gay-Lussac. * (Read to the French Institute on the 1st of August, 1814.) I HAVE already, in the sittings of the 6th and 20th of December, 1813, read to the Class the result of my researchest on the substance discovered by M. Courtois, to which I proposed to give the name of iode, on account of the beautiful violet colour of its vapour. To these researches, the object of which was to determine the nature of iodine, and the situation in which it ought to be placed with respect to other bodies, I have added new experiments, which I have now the honour to communicate to the Class. If there be no occasion to apologize for the length of time which has elapsed since I read my first experiments, I must at least beg your indulgence for the details into which I am about to enter. I regret that my labours have lost part of their interest, by appearing after those of M. Vauquelin, with which I was unaccquainted when I drew up my memoir. But it will be at least a satisfaction to me, if, in the subjects which we have treated in common, I have in general drawn the same conclusions as he has done.

Properties of Iodine. lodine when in a solid state is greyish black; but its vapour has a fine violet colour. Its odour is exactly that of chlorine, weakened. It is often in scales similar to those of micaceous iron ore, sametimes in rhomboidal plates, very large and very brilliant. I have obtained it in elongated octohedrons about a centimetre in length. Its fracture is lamellated, and it has a fatty lustre. It is very soft and friable, and may be rubbed to a fine powder. Its taste is very acrid, though it be but very little soluble in water. It gives a deep brown stain

to the skin, but this colour is soon removed. Like chlorine it destroys vegetable colours ; but with much less energy. Water dissolves about one seven thousandth part of its weight of iodine, and acquires an orange yellow colour. The specific gravity

a

* Translaed from the Annals de Chimie, vol. xci. p. 5. July 1814, # Printedin the Annals of Philosophy, iii. 106.

« PreviousContinue »