history of this alkaline substance, and the method we have adopted in analyzing the stavesacre."

Paris, July 12, 1819.

Annales de Chim. x1. 188.

3. On the action of Nitric Acid, Chlorine, and Iodine, on Uric Acid, by M.Vauquelin.-For eight months I have employed all my leisure moments in those researches on the action of nitric acid, chlorine, and iodine, on uric acid, announced by M. Brugnatelli, and repeated by Dr. Prout. To detail here all the experiments I have made on this subject would be too tiresome, but I shall give the principal results of them. I have not been able to gather any thing useful from the memoirs of Messrs. Brugnatelli and Prout; because, one of these gentlemen has not given. the process which he followed for the preparation of what he calls purpuric acid, and what the other has said appears unintelligible to me, and because these chemists contradict each other on a great number of points, respecting the properties of the acid they have discovered.

I will first observe that uric acid suffers the same changes, and gives the same products, whether it be treated with nitric acid, chlorine, or iodine; but these products change in their nature according as the action of the agents is continued to a lesser or greater extent. If this action is retarded, a large quantity of a particular colouring matter is formed, and very little acid; if it is carried farther, without passing certain limits, little colouring matter is obtained, but a much larger quantity of acid; and finally, if the action be continued for a long time, these two substances disappear, and oxalic acid and ammonia only are obtained. Thus in varying the quantity of these bodies, and the manner in which they act on the calculous matter, we may obtain at pleasure various products, and in proportions very different.

The best proportions to produce the 100 parts of nitric acid, at 34° (S. G.

colouring matter, are 1.307?), mixed with acid, at a low heat.

100 parts of water, and 50 parts of uric The solution obtained has a fine scarlet colour. If fresh quantities of nitric acid be added to it, and boiled, the red colour

disappears, and a yellow one succeeds. If into the first solution, milk of lime, very finely mixed, be introduced, the lime dissolves, but on approaching the point of saturation, a red crystalline and brilliant substance is deposited. The same milk of lime, put into the second solution, or that to which nitric acid has been added, produces the deposition of a white or pale yellow substance, also crystallized, and of a brilliant appearance. This last substance is a combination of the lime with the new acid, formed by the action of the nitric on the uric acid. The first is a similar combination, containing a certain quantity of colouring matter, formed also at the expense of the uric acid.

After purifying this salt by repeated crystallizations, I decomposed it by a sufficient quantity of oxalic acid, and obtained the new acid in its pure state. It is white, fusible, of an acid taste, readily soluble in water and alcohol, saturating but small quantities of bases, and giving, when decomposed by heat, hydrocyanate and carbonate of ammonia, empyreumatic oil, and charcoal. It causes white precipitates with the acetate of lead, muriate of tin, and nitrate of mercury; but it does not precipitate nitrate of silver, nor does its saline combination affect that test. Dissolved in nitric acid, and evaporated to dryness, it does not produce a red colour.

The combination of the calculous acid with lime does not precipitate solution of silver, but the same combination united to colouring matter precipitates the salt of silver of a fine purple colour. I took advantage of this property to separate the colouring matter from the acid, I mixed a coloured solution with nitrate of silver, until no further precipitate was formed; it was of the finest purple, and as soon as it had fallen, and the fluid become clear, they were separated, and the deposit washed several times; being afterwards mixed with a small quantity of water, it was decomposed by the necessary quantity of hydro-chloric acid. The colouring matter thus precipitated by the silver, the acid to which it was united was found in the fluid; for, on adding to it a little lime, a white precipitate was formed, being the combination with silver.

The chloride of silver being separated, I obtained a fine red fluid, in which there was neither silver nor hydro-chloric acid. The following are the properties of this colouring matter; it is neither acid nor alkaline; acids destroy its colour, making it yellow, and nothing can restore its first tint. If only a small quantity of acid is added, the colour passes to scarlet before it disappears. The alkalies, and the oxides of lead, silver, and copper, convert it to a violet colour, but do not destroy it. Lime does not act strongly on its colour; its combination with it preserves the red tint. It adheres to metallic oxides, neutral salts, and to animal and vegetable substances; but it cannot long resist the action of air and the sun, which change it to yellow.

It follows from what I have detailed, that by the action of nitric acid, chlorine, and iodine, on uric acid, there is formed a peculiar acid, which is without colour, and an azotated colouring matter, which is not acid, but which has a stronger analogy to the bodies of this class than to the alkalies. It is this colouring matter, which, mixed with the peculiar acid of the calculus, has made Messrs. Brugnatelli and Prout believe the acid itself was coloured, and has caused one to give it the name of erythric acid, and the other purpuric acid; names, which we may observe, are not applicable to it.

I have made a great number of experiments on this acid, and its combinations with different bodies; I have also submitted the colouring matter to many tests, of which some have given me curious results. I have carefully examined the manner in which nitric acid, chlorine, and iodine, act on uric acid, and the various bodies which, according to circumstances, result. That which required the most time was a search after some simple and exact method of separating the acid and colouring matter from each other. I shall shortly publish these experiments, with the necessary details.

As names are required for these two substances, I shall propose, for the present, for the acid, the name of peroxygenated uric acid, and for the colouring matter, that of erythrine.

*Better oxy-uric acid.

4. Persian Metallurgical Processes.-The following metallurgical operations were described in the laboratory of the Royal Institution, by Oostad Muhammed Ali. From the clear manner in which he illustrated the description, by the disposal of the apparatus about him, there is not much chance of any important error or omission in this account of them.

Persian Method of purifying Silver.—A sort of basin is made, either by excavating the ground, or by arranging stones in a circle. This is from nine to twelve, or fourteen inches wide, and is incomplete at the side in one place, for the reception of the fuel, which, by its combustion, is to melt the metal. The fuel consists of two large and long logs of wood, which are placed with their ends in the aperture on the edge of the basin. These ends are lighted by putting a little burning fuel on them, and then the blast from a pair of bellows is directed on to and over the fire, so as to direct the flame and heat into the basin, in the manner, indeed, of a large blow-pipe. Lead, containing silver, or impure silver with lead, is then placed in the basin, which being soon melted and heated by the flame, is purified as by common cupellation. The litharge is forced off to the sides as it is formed, and either absorbed or lost, and as the wood burns away before the jet of air, the logs are thrust onwards, until all is consumed; then fresh logs are applied, if necessary, or the process is stopped, as may be found expedient.

Manufacture of Steel in Persia.-Oostad Muhammed Ali thus describes Persian steel-making:-Iron is brought from the mountains, but he does not know how it is obtained: a square place is built up, about four feet in the side, and five or six feet high, the walls being eight or nine inches thick; stones of a slaty kind are put across this on the inside, about eighteen inches from the bottom, so as to form a grate; below this is a chamber for the reception of the melted steel, and above it is placed the iron in bars, and charcoal intermingled together. There are three apertures just above the grate into the furnace, into. which air is propelled from bellows, worked by men sitting; a 'fire is lighted, and the heat raised, fresh charcoal is thrown on as that in the furnace burns away; and as the iron becomes

carbonized, it melts and falls through the grate as fluid cast steel, into the chamber beneath, from whence it is taken and cast into ingots.

From three to four hundred weight of iron is placed in such a furnace, and there is a loss of about one-third from oxidation, and adhesion to the sides: The operation requires from two to three days, with constant blowing. M. Muhammed described the charcoal as being exceedingly hard and heavy, and very unlike our charcoal, but did not know of what wood it was made.

5. Process for obtaining pure Nickel.-The following is a process recommended by Dr. Thomson, for procuring pure. nickel-" I take a quantity of the brittle reddish alloy, well known in commerce by the name of speiss. This alloy is chiefly an arseniuret of nickel, though it probably contains also, occasionally at least, several other metals. Upon the speiss. reduced to a coarse powder, I pour a quantity of dilute sulphuric acid, place the mixture in a Wedgewood evaporating dish upon a sand bath, and add the requisite quantity of nitric acid at intervals, to enable the acid to act upon the speiss. By this process I obtain a deep grass-green liquid, while a considerable quantity of arsenious acid remains undissolved. The green liquid, carefully decanted off the arsenious acid, is evaporated on the sand bath, till it is sufficiently concentrated to yield crystals. It is then set aside in a cool place. A deposit of beautiful crystals of sulphate of nickel is obtained. By concentrating the liquid still further, more crystals of sulphate of nickel fall, but after a certain time the liquid, though its colour continues still a dark green, refuses to yield any more crystals of sulphate of nickel. By evaporating it to the required consistency, and then setting it aside, a very abundant deposit is made of an apple-green salt, which adheres very firmly to the evaporating dish. I took this matter at first, from its colour, to be arseniate of nickel; but I found it, on examination, to be a double salt, consisting of sulphate of nickel and arseniate of nickel, united together. I endeavoured to get rid of the VOL. VIII.

M