salts which I have published, he will have been struck with some other anomalies of a similar nature to those belonging to the salts of lead; but I forbear touching upon them at present, till we are in possession of more perfect analyses than have been hitherto published.

2. Certain salts have been analyzed, the composition of which, when stated in symbols, presents us with the anomaly of 1 atoms of one substance combined with one atom of another. Thus subsulphate of iron is composed thus, 1 (S O) + 1 (FO2); or it contains one integrant particle of sulphuric acid and 14 integrant particle of black oxide of iron. As such a composition is obviously impossible, it is clear that in such cases a certain number of integrant particles of sulphuric acid must be combined with a certain number of integrant particles of oxide of iron. If we multiply by two, the anomaly will disappear. We shall then have 2 (S O3) + 3 (FO); that is to say, the salt is a compound of two integrant particles of sulphuric acid and three integrant particles of black oxide of iron. Such combinations do not present any thing incompatible with the atomic theory, which admits of such combinations; but they constitute exceptions to one of the general laws which Berzelius has deduced from his numerous analyses. The law is, that in all inorganic compounds one of the constituents always enters in the state of a single atom. In the subsulphate of iron there is no single atom, either simple or compound. It consists of 12 atoms of oxygen, three of iron, and two of sulphur; or of two integrant particles of sulphuric acid and three integrant particles of black oxide of iron. The composition of the subsulphate of copper may be explained in the same way. Its symbol is 1 (S O3) + 14 (CO2), or one integrant particle of sulphuric acid combined with 14 integrant particle of black oxide of copper. If we multiply by two we obtain 2 (S O3) + 3 (C O2), which I conceive to be the real constitution of the salt; namely, a compound of two integrant particles of sulphuric acid with three integrant particles of black oxide of copper. The subarseniate of lead admits of the same explanation. Its symbol is 1 (As O3) + 1 (PO), or one integrant particle of arsenic acid combined with 14 integrant particle of yellow oxide of lead. When we multiply by two we obtain 2 (As O3) + 3 (P Oo); that is, two integrant particles of arsenic acid united with three integrant particles of yellow oxide of lead.

Various other similar examples might be adduced; but they are all explicable in the same way. They appear to me to constitute so many exceptions to Berzelius's law above-mentioned, and to show that it does not hold so universally as he had supposed.

3. Professor Berzelius has just favoured the chemical world with an analysis of a considerable number of the vegetable acids, and some other vegetable substances. That these experiments have been conducted with the greatest care is evident from the details into which Berzelius has entered; nor have I the least doubt, from the uncommon precision which characterizes whatever is done by this

very skilful chemist, that his results furnish very near approximations to the truth; but from the extreme difficulty attending such analyses, I do not conceive that perfect precision can be attained at first; but I think that the atomic theory furnishes us with such additional checks that, by a judicious application of them to the constitution of these acids as determined by Berzelius, we may obtain results approaching exceedingly near the truth. I shall at present apply that theory to the investigation of the composition of oxalic acid.

According to Berzelius, that acid is composed as follows:

But as I consider the weight of an atom of hydrogen as twice as great as Berzelius makes it, we must, in order to represent the composition of this acid according to my numbers, double the number of atoms of oxygen and carbon which it contains. It will then be composed of

So that it is a very complicated body. The weight of an integrant particle of it must be 18 140. We might, indeed, reduce the number of atoms in this acid to 11 by doubling the quantity of hydrogen, obtained by Berzelius; for the difference seems to be within the limits of the unavoidable errors to which such experiments are liable. But Berzelius does not think that he could have committed any such error. Let us, therefore, have recourse to another method of determining the weight of an integrant particle of oxalic acid.

From the analysis of oxalate of lead made with great care by Berzelius it appears to be a compound of

Oxalic acid

Yellow oxide of lead

100
307.5

Now there can be no doubt, from a comparison of all the genera of salts hitherto examined, that oxalate of lead is a compound of two integrant particles of oxalic acid and one integrant particle of yellow oxide of lead; so that to find the weight of an integrant particle of oxalic acid we have this proportion:-307.5: 27.974: 4.548 an integrant particle of oxalic acid. Now this is just the fourth part of the weight of that acid resulting from the

100

2

analysis of Berzelius; yet it is the weight of an integrant particle of oxalic acid, as any one may satisfy himself by examining the composition of the oxalates, a table of which I subjoin for the satisfaction of the reader :

29.902

Oxalate of barytes

strontian

alumina
yttria
glucina
zirconia

copper

....

potash-and-copper. 2 ox + 1 p + lc.
soda-and-copper.. 3 ox+1s+lc. 32.410

All these salts corroborate the weight of an integrant particle of oxalic acid as deduced from the analysis of oxalate of lead. Here, then, we have two experiments of Berzelius, which are inconsistent with each other; namely, the analysis of oxalic acid and the analysis of oxalate of lead. Both were made with the greatest care; but as they are inconsistent with each other, they cannot both be correct, and there can be no hesitation about which of them

ought to be followed. The analysis of oxalate of lead is much simpler, not liable to the same uncertainties, and susceptible of greater exactness than the analysis of oxalic acid. We ought, therefore, to be guided by it; especially as it is corroborated by various other very exact analyses, as those of oxalate of potash, oxalate of ammonia, and oxalate of strontian. But if we adopt this determination, and compare it with the analysis of oxalic acid, we shall find that this acid must be composed of six atoms; namely, three atoms oxygen, two carbon, and one hydrogen; and its composition will be

Now this is the composition of the acid which I deduced some time ago by comparing my own analysis of oxalic acid with the composition of oxalate of lead as determined by Berzelius. obtained for the composition of oxalic acid

I

My experiment was conducted with great care, and I still consider my result as nearer the truth than either that obtained by GayLussac and Thenard or by Berzelius. My excess of hydrogen amounts to about one per cent., and was probably owing to the salt which I employed in the analysis not being quite free from water. Mr. Dalton has adopted the same constitution of oxalic acid with the above, and probably he has been led to it by the same mode of reasoning from which I deduced it.

I shall take another opportunity of examining the other acids analyzed by Berzelius, by applying to them the test of the atomic theory. What I have here said is sufficient to show us that the most cautious and elaborate experiments are not sufficient of themselves to make us acquainted with the composition of these intricate bodies; though such experiments afford us considerable assistance, and, when compared with the structure of the salts as explained by the atomic theory, will generally be sufficient to give us all the information respecting the constitution of these acids which we can expect to obtain.

ARTICLE V.

Observations on the Uses of the Dorsal Vessel, or on the Influence which the Heart exercises in the Organization of articulated Animals, and on the Changes which that Organization experiences when the Heart or the Organ of Circulation ceases to exist. By M. Marcel de Serres.

(Continued from Vol. iv. p. 355.)

I BEGAN the examination of the dorsal vessel with those species in which we see it beating externally. Among those I chose the larvæ of the coleoptera and lepidoptera. The larva of the geotrupa nasicornis, being very common, seemed proper for my object. The dorsal vessel of this species is elongated and cylindrical. When separated from the muscles and fatty membranes which surround it, we see that its diameter is the same in almost the whole of its length, being only a little contracted at the two extremities. Having fully ascertained this disposition, I endeavoured to ascertain if there were any ramifications. For this purpose I examined it with the greatest attention, and with the best glasses. The contractions were always confined to the dorsal vessel, and never extended beyond the canal which runs along the back. I then placed this vessel under the lens of my microscope, and could not perceive any ramifications, not even in the membranes which surround it. In vain I endeavoured to find some trace of them in the membrane of the intestinal tube, the fibres of the muscles, especially in those of the rings of the abdomen and mandibles, which ought to have presented them, if any had existed, in consequence of the energy of their contraction, and the need which these organs have of vessels.

I then examined the dorsal vessel of the geotrupa nasicornis et punctata; but all my attention was unable to discover the least ramification. I subjected to the same examination a very considerable number of coleopteræ, the largest that I could procure, as the ateuchus semi-punctatus, cetonia aurata et fastuosa, scarites gigas, cerambyx heros, blaps gigas, and mortisaga. In all of them I observed the dorsal vessel without any ramifications. These dissections, however, convinced me that, without a certain attention, ramifications of that vessel may be supposed to exist, on account of the colour and disposition of the hepatic vessels, which, being long and almost capillary, spread over every part of the body, and are often found fixed to it after the intestinal tube has been removed. To determine with certainty this disposition, we must allow the intestinal tube to remain, and dissect in water. This liquid lifts up the hepatic vessels; so that it becomes easy to follow them to their insertion.

Though I could not perceive any ramifications in these species, I was not entitled to conclude that they did not exist in insects. I