equivalent of the acid will suffice, with rigour, to make a choice from amongst them.

Now one gramme of the oxymate of baryte gives 0.636 of the sulphate of baryte; and on the other hand, this salt, which contains water of crystallisation, leaves it completely disengaged when we submit it to a current of dry air heated to a temperature of 150o, which commences its decomposition, and to disengage the traces of ammonia.

It results, from these experiments, that the salt of baryte contains 3 equivalents of water, and that the chemical equivalent of anhydrous oxamic acid is 998, a number from which may be deduced, for the composition of oxamic acid, the following formula :-C4 O' H1 Az2.

The number 1.002, which gives the calculation for the atomic weight of such an acid, approaches very nearly in effect to 998, determined by direct experiment.

The analysis of the salt of baryte confirms this composition:1 gramme of oxamate of baryte, analysed by the oxyde of copper, produced 0.394 of carbonic acid, and 0.279 of water.

One gramme of the same salt furnished 67 cubic centimetres of azote, measured at the temperature of 14°, and under the pressure 0.755. By diminishing the water produced, that which the salt contained in the state of water of crystallisation, and adding to the carbonic acid obtained, the portion which the baryte should retain, by admitting that it remains quite entire in the state of carbonate, we find, for the composition of oxamic acid :

The analysis of other oxamates confirms that of the oxamate of baryte.

If we boil this compound with a proportionate quantity of sulphate of ammonia, in solution, we obtain, by evaporation and cooling down, a salt which crystallises in small prisms grouped in stars, and which contains only the equivalent of water which is indispensible to the constitution of ammoniacal salts.

In fact, an undetermined quantity of this salt, burnt by the oxyde of copper, has given carbonic acid and azote, sensibly, in the proportion of 2 volumes of the former for 1 volume of the latter; and 0.500 of this salt have furnished:-carbonic acid, 0.407; water, 0.260.

We deduce from these numbers, for the analysis of ammoniacal salt :

A solution of oxamate of ammonia and oxamate of baryte, treated by nitrate of silver, furnished an abundant gelatinous mass (magma), demi-transparent, and which soon becomes opaque. This precipitate is completely dissolved in the liquor when we raise the temperature, and this, by its cooling down, leaves deposited silky crystalline needles, white, but which recover the metallic silver at their surface, and also become blackened when they are exposed to the action of light. A temperature of 150° produces the same effect amongst them, but does not eliminate any water.

0.982 of this salt, decomposed by the fire, leaves 0.540 of metallic silver. We deduce from it, for the equivalent of the acid, 1.005; the calculation gives 1.002.

1.104 of the same salt have produced:-carbonic acid, 0.495; water, 0.116.

0.639 of the same compound have given :-azote, 39 cubic centimetres, temperature 17°, barometer 0,7645, whence we deduce for the composition of the acid contained in the salt of silver :

:

Each of these salts, of which I have already spoken, will serve to

isolate the oxamic acid.

That of baryta, treated cold, by a proportionate quantity of sulphuric acid, much diluted with water, gives, by evaporation of the liquid executed at the ordinary temperature, free oxamic acid.

A saturated solution of oxamate of ammonia, hot, treated by a proportionate quantity of sulphuric acid, and suddenly cooled, also leaves deposited oxamic acid, under the form of a white powder, in a small degree soluble in cold water.

In fine, the oxamate of silver, on which we cause to pass a current of dry chlorhydric acid, undergoes, by a slight elevation of temperature, a decomposition, which is effected with an energetic disengagement of heat, and with the production of chlorure of silver

and free oxamic acid. In driving away the excess of chlorhydric acid by a current of dry air, and by treating the mixture of chloride of silver and oxamic acid by alcohol absolutely boiling, we obtain, by the evaporation of this liquid, oxamic acid, under the form of a granulous powder, colourless when we moderate the action of the chlorhydric acid on the salt of silver, and avoid too great an elevation of temperature; but slightly coloured in yellow, if this precaution has been neglected.

0.335 of this acid, burnt by the oxyde of copper, have furnished 0.325 of carbonic acid, and 0.120 of water.

0.318 of this acid have produced azote 46°, temperature 18°, pressure 765,2; which gives, as the analysis of the free acid and its formula, calculated on the supposition that it contains 1 equivalent of water:

The analysis of the oxamates and of the free oxamic acid fully agree, leaving not the least doubt on the composition of this compound. Anhydrous and such as it exists in the dry oxamates; the oxamic acid contains the elements of bi-oxalate of ammoniac, also anhydrous, less those of one equivalent of water. It is with bioxalate of ammonia that this oxamide is neuter to the oxalate. its anhydrous state, oxamic acid will thus be isomeric with the alloxane of M. M. Liebig and Töhler. The isolated acid of these salts contains one equivalent of water, and contains the elements of bi-oxalate of anhydrous ammonia.

In

Like the amides to which they assimilate, oxamic acid retakes the elements of this equivalent of water, and thus reproduces the compound which has given birth to it. This return to the primitive state is brought about by the action of water, aided by the concurrence of heat. But whilst a temperature of 200° is necessary to transform the oxamide into the oxalate of ammonia, by the action of water alone, this liquid only requires a temperature of 100 to produce on the oxamic acid an analogous decomposition. Likewise, when we attempt to isolate the oxamic acid in decomposing, in a hot state, by sulphuric acid, a solution of oxamate of baryte, and evaporate the liquid at an elevated temperature, we only obtain bi-oxalate of ammonia. The decomposition is complete, and thus I am perfectly assured by analysis of the product of this reaction.

Among the azotic acids known to chemists, there is one to which the oxamic acid nearly approaches by its nature, and the mode of

the decomposition which it undergoes on being brought into contact with water; this is the oxaluric acid, which contains the elements of two equivalents of oxalic acid and one equivalent of urea, less those of one equivalent of water, which becomes transformed into oxalic acid and oxalate of urea by the action of water, at its boiling temperature. This analogy of nature, and this similarity in the mode of decomposition, coinciding further with a great resemblance in their properties, there exists, in fact, between the oxaluric acid and the oxalurates, oxamic acid and the oxamates, the most strict connexions.

The oxamic acid, which is formed during the decomposition of bi-oxalate of ammonia by fire, may be obtained, likewise, by submitting to the action of this agent the neuter oxalate of this base. In his work on oxamide, M. Dumas has remarked that the action of heat on the neuter oxalate occurred by disengaging at first the ammonia, and that it was thus on a salt, with excess of acid, that the decomposition which gives rise to the oxamide becomes realised further on. It was from thence natural to research, among these products, the presence of oxamic acid, which I have found again in the fixed residue of this reaction, determined by a well-managed heat.

This mode of the action of fire on the oxalate of ammonia differs a little from that which this agent exercises on the mellitate of this base. After the recent researches of M. Töhler, the mellitate of ammonia, exposed to the action of a heat of 150°, at first loses ammonia, and is transformed into mellitate acid, which in its turn undergoes a decomposition, at the end of which it produces paramide and euchronic acid. But neither one nor the other of these compounds correspond to the oxamic acid which I have described. This acid is bi-oxalate of ammonia, less the elements of one equivalent of water; paramide, on the contrary, is bi-mellitate of ammonia, less the element of two equivalents of water; in fine, euchronic acid will be trimellitate, less the elements of three equivalents of this liquid.

The knowledge of the oxamic acid appears to me to be susceptible of fixing the opinions of chemists on the true nature of some ethereal compounds, of a constitution still uncertain, and of which the principal species have been described by M. Dumas and his co-labourers. I wish to speak of oxamethane and of analogous compounds, which furnish the oxalic ethers of divers alcohols.

These compounds, which contain in their equivalent the elements of an equivalent of oxamic acid, and of an equivalent of ether, may be conceived as ordinary compound ethers, into the constitution of which the oxamic acid enters, which forms the object of these researches.

In order to justify by facts this supposition, it is necessary to observe two things—either to obtain oxamethane and the analogous composition by etherification, made to operate directly by means of the free oxamic acid, or to withdraw the oxamid acid itself from the

decomposition of these ethereal compounds. I have not succeeded at present in obtaining oxamethane by the action of oxamic acid on alcohol, though some observations, which are yet imperfect, make me regard this transformation as possible; but I have the power, in retaliation, easily to extract oxamic acid from oxamethane and from analogous compounds.

In their researches on oxamethane, M. Dumas and Polydore Boulay have proved, that by ebullition with water this compound becomes transformed into alcohol and bi-oxalate of ammonia. But that which I have learned on the easy decomposition of oxamic acid, by the intervention of water at 100°, permits me to suppose that this bi-oxalate proceeds from a decomposition, secondarily undergone by the oxamic acid itself, produced direct from this reaction.

This supposition is, in fact, justified by experience. If we submit to ebullition an aqueous solution of oxamethane, by taking care to add, drop by drop, to the boiling liquor, a portion of diluted ammonia, in such a manner as to neutralize by this base the acid which is developed by ebullition, the liquors, thus maintained in a state of neutrality almost complete, will no longer contain anything when the oxamethane has been decomposed, except the oxamate of ammonia. Precipitated by the azotate of silver, it produces a gelatinous magma, which, by its appearance, its solubility in cold water, and the aspect of the crystals which it leaves deposited on cooling down, presents such an identity of properties with the oxamate of silver, that it is impossible not to conclude thence an identity of nature which justifies, for the remainder, the analysis of this salt.

0.470 of this salt, submitted to the action of heat, have left for a residue 0.257 metallic silver. This same quantity of oxamate of silver, obtained directly, has furnished 0.258.

0.585 of salt of silver, proceeding from oxamethane, have furnished carbonic acid, 0.270;, water, 0.070.

0.507 of the same product, have furnished 32 cubic centimetres of azote, temperature 17°, pressure 757,8.

These results give, for the analysis of the salt of silver, numbers approaching very near to those which were furnished by the analysis of the oxamate of silver obtained in a direct manner.

The oxamethylane and oxamylane, composed from amylique alcohol, correspond to oxamethane, and which I shall make known in a short time; produce the same effects, and give place to the production of the same acid, in the decomposition which they undergo by ebullition with water.

This mode of decomposition of oxamethane has been alluded to by M. M. Dumas and Polydore Boulay. In their work, so remarkable on the compound ethers, they prove that baryta, by acting on the oxamethane, disengages ammoniac, and forms a salt slightly soluble, but susceptible at all times of crystallization by the concentration of the liquor. There is no doubt that this salt, the study of which the series of works executed by those chemists did not permit