This is the first instance of isomerism occurring in substances belonging to the class of organic bases.

One very interesting conclusion regarding the action of medicinal substances appears to be deducible from these results, that similarity of physiological properties does not depend upon similarity in the proportions of their constituents. It seems probable that the mode in which their atoms are grouped has an important share in modifying their physiological actions; for in the present instance we have the same number of atoms both in morphia and bebeerine, but in the one producing a white crystalline body of narcotic qualities, in the other a yellow amorphous resinous-looking substance, acting as an anti-periodic. The difference in their physical properties in fact proves that their elements are differently arranged.

We have not been enabled to examine sipeerine, the substance left behind when pure bebeerine is dissolved out by means of æther. It occurs in very minute quantity, and requires a very tedious repetition of the treatment with æther to free it from the last traces of bebeerine. There seems, from some trials which we have made, good ground for believing that it is a distinct alkali, but it has not been obtained in sufficient quantity to enable it to be subjected to ultimate analysis.—Proceedings of the Chemical Society.

ON THE PROPERTY POSSESSED BY LITHARGE IN FUSION OF DISSOLVING OXYGEN;

And on some Circumstances accompanying the Production of Litharge in the Process of Cupellation on the large scale.

BY M. F. LEBLANC.

Ir is known that the process of cupellation, as performed in lead works, consists in separating silver from the lead, the latter metal being eliminated in the state of oxide. Cupellation on the large scale, or refinery, as it is called in some works, differs from the process as performed in the assayers' laboratory, inasmuch as the litharge, or protoxide of lead, formed by the action of atmosperic oxygen on the fused lead at a high temperature, instead of being separated by absorption into the substance of the cupel, is removed from the furnace as it is formed, by means of a trench on a level with the bed of the furnace. This is the mode of producing litharge. The material of which the furnace is formed ought to be such as to prevent absorption and resist the solvent action of the fused litharge.

The atmospheric oxygen is projected on to the surface of the fused metal by a forced current of air.

During a stay I recently made at Poullaouen, I assisted in several operations for refining lead containing silver, and made some observations which may not, perhaps, be devoid of scientific interest.

It is known that litharge, to be adapted for commerce, should possess certain properties, which can, to a certain extent, be developed at will, by properly regulating the rapidity of the cooling of the litharge which flows from the furnace. Litharge, when cooled rapidly, is yellow or greenish-yellow; but when cooled slowly, in the manner indicated by M. Fournet, it changes structure and colour, and acquires those properties which make it generally esteemed in commerce.

It is to the study of the physical and chemical changes which take place during this transformation, that I have directed my attention. With this view I have performed some experiments which I am about to describe, and which, I think, will modify the opinion previously formed of these phenomena.

M. Fournet admits that the fused litharge may absorb the oxygen, and become superoxidized, and that at a higher temperature than that at which

minium is decomposed. This Chemist considers that the red litharge, sought in commerce, owes its properties to an excess of oxygen.

M. Fournet's opinion has not been adopted by M. Thénard. This illustrious Chemist has repudiated the theory of the superoxidation of the lead at the temperature of the cupelling furnace, and considers it as possible that a solution of oxygen is effected in the litharge, similar to that which occurs in the case of fused silver. This oxygen will unite with the protoxide of lead when slowly cooled, and will be disengaged if rapidly cooled.

M. Pernolet, director of mines and works at Poullaouen and Huelgoat, had already remarked that the fused litharge held a gas in solution, varying in quantities according to the duration of the operation, and that this gas had a tendency to escape at the moment of solidification. The facilities he was good enough to afford me, enabled me carefully to collect specimens of litharge of different degrees of purity, and in different states: I also collected and analysed the gas as it escaped. These experiments fully confirm the anticipations of M. Thénard, as regards the solution of the oxygen; for the collected gas possesses the properties of oxygen nearly pure. The analysis indicated from 82 to 90 per cent. of oxygen. It is probable that the presence of a little nitrogen may be due to the accidental admixture of a small quantity of air. In fact, on repeating the experiment under similar circumstances, with silver taken from the refiners' cupel, I did not find above 90 per cent. of oxygen absorbable by heated phosphorus.

The quantity of oxygen dissolved in a given weight of litharge, is too great to admit of the possibility of silver contained in the litharge being the solvent of the gas; this proportion is not less than nineteen and a half cubic inches of the gas to 2lbs. 3ozs. avoirdupois of litharge, notwithstanding the necessary losses in its collection. But the specimens of litharge operated upon, even those most rich in silver, did not contain more than the one-thousandth, or fifteen-hundredth of that metal.

It appears to me then established, that the litharge, inoxidizable at the temperature of the furnace, may, under the influence of a current of air, dissolve oxygen in the same manner as silver, and that it comports itself as most liquids do when in contact with gases.

Black or impure litharge, is, according to my experiments, unfit for solving gases ;at least the quantities found were so small, that their presence might be considered as accidental; analysis also, indicated the proportions of oxygen and nitrogen to be the same as in atmospheric air. This circumstance will not appear surprising, when it is considered that this kind of litharge contains the elements of oxidizable sulphurets.

Ought the solution of oxygen in a liquid, in a state of igneous fusion, and which has no chemical action on the gas, to be considered as a general phenomenon, or confined to the cases of litharge and silver? This is a question which my experiments may perhaps tend to solve. The phenomenon alluded to, may be found to hear on some geological questions, and may therefore merit attentive study.

To confine myself, however, to the subject of this paper, I shall proceed to consider what occurs with the fused masses of litharge on flowing out of the furnace, and to discuss the part which the imprisoned oxygen plays in these masses on their solidifying, which ends in a gradual change of their internal

structure.

At Poullaouen, the litharge on running out of the furnace, and when it has acquired a sufficient degree of purity, is collected in iron pots of a conical form, and capable of containing about sixty pints. The litharge soon solidifies on the surface, and assumes a yellow or greenish-yellow colour. In the course of a few hours, sometimes in half an hour, the mass breaks, splitting in every direction, and it becomes a friable, crystalline mass of a decided red colour. The surface alone, which solidifies quickly, retains its

colour and coherence. The red litharge, which is carefully selected, is that alone which is saleable; the yellow litharge is put on one side, and reserved for refusion.

Sometimes the phenomenon occurs more suddenly, a sort of explosion takes place, which, in the first place separates the conical mass of litharge into several large blocks; at the same time a certain quantity of litharge is projected from the interior in a liquid or pasty state.

It appears to me that the imprisoned oxygen acts mechanically during the solidification of the litharge, producing the phenomenon of exfoliation.

It is worthy of remark, that all circumstances tending to diminish the rapidity with which the litharge cools and becomes solidified, tend also to augment the proportion of red litharge formed. When it is made to flow into vessels of too small capacity, the litharge cooling too quickly remains yellow, and there is no exfoliation.

M. Fournet considers that the red litharge contains more oxygen than the yellow, and that it owes its colour to the presence of a certain quantity of minium. Many specimens afforded him undoubted evidence of the presence of minium.

M. Thénard and most other Chemists also attribute the colour of commercial litharge to the presence of a small quantity of minium.

Without wishing to deny the possibility of the litharge when slowly cooled, under certain circumstances, absorbing oxygen, and giving rise to the forma tion of minium, a fact well attested, I believe nevertheless, I shall be able to show that we must seek for another explanation of the phenomenon of exfoliation in the masses of litharge, and the production of the red litharge. The following are the experiments on which I found this assertion :—

1st. The red litharge which I have examined, has not given off oxygen on the application of heat.

2d. This same litharge, examined with much care, by the use of pure nitric acid, did not yield any puce coloured oxide; a trace of minium added to the yellow litharge, without sensibly changing the colour, may be detected by the same mode of examination.

3d. Red litharge, heated to a temperature at which there is no disengagement of oxygen, and quickly thrown into water, becomes yellow.

Experience shows that these variations in the structure and colour of litharge, resulting from the conditions of temperature, accompanying its production, do not depend on any change in its chemical composition, but chiefly on isomeric or dimorphous modifications, similar to those which constitute the difference between vitrious and opaque arsenious acid, barleysugar and sugar-candy, red and yellow iodide of mercury, &c.

According to the experiments which I have made, these modifications in the structure and colour of the protoxide of lead, have relation to the densities of the different specimens. Exfoliated red litharge is less dense than the crystalline yellow. In my memoir on this subject, some tables will be found relating to the various experiments which were made.

To recapitulate, the facts stated in this paper, appear to me to establish1s. That oxygen may be dissolved in fused litharge, as it is in silver, and and that it does not enter into combination as a superoxide; nitrogen may, perhaps, be at the same time dissolved in small proportion.

2d. That there only exist between the yellow and red litharge, physical differences of structure, of colour, and of density, which do not in the least affect their chemical composition. These different varieties may be produced at will, without resorting to fusion, by regulating the temperature and the rate of cooling.-Journal de Pharmacie.

OBSERVATIONS ON THE ACTION OF ANIMAL CHARCOAL.

BY ROBERT WARINGTON, ESQ.

ABOUT twelve months since a friend requested that I would undertake the performance of an experiment for him, which, if successful, he considered might prove of importance. The idea had occurred to him in passing one of the large breweries, that, from the greatly increased demand for pale ale, such as is exported to India, as a beverage for home use, it would be practicable to discharge the colour from the ordinary beer by artificial means, and thus obtain the desired object. What rendered this, he said, the more important, was the difficulty he had heard expressed by persons interested in the matter, in preparing an article sufficiently pale for the purpose of sale, the malt employed requiring to be made expressly for this quality of beer. To effect this desideratum, he considered that all that would be required would be to pass the fluid through a medium of animal charcoal, and that the ordinary amber colour of ale would be thus partially removed. I undertook to make his experiment for him, at the same time telling him that I thought the beer would be rendered very flat and the flavour much injured, but certainly not anticipating what followed. The method adopted, as presenting the least objectionable points to the successful attainment of the desired object, was to pass the cold ale through a stratum of animal charcoal placed on a paper filter, and to repass the filtrate through the same medium until the required effect was obtained; the ale operated upon was highcoloured, and had a bitter taste and the fine aroma of the hop. The colour was rapidly removed, but the ale was found on tasting extremely vapid and flat, and the whole of the bitter flavour was found to have been also abstracted. Not being prepared for this result, I was surprised at the rapidity of the action, and resolved immediately to carry on the investigation by substituting other and stronger bitters in the place of the hop. For this purpose a quantity of the ale which had previously had the flavour of the hop removed by charcoal was prepared, one portion of which was boiled with bruised gentian root and another with the raspings of quassia wood; but on passing these decoctions when cold through the charcoal filter as before, the whole of the intense bitter flavour which they had imbibed rapidly disappeared.

It now occurred to me that this property of animal charcoal might be made of considerable utility to the Chemist, as, from all our information up to the present time, it does not affect the active alkaline organic principles, and, therefore, should prove the means of separating the bitter of the hop and other materials from that of strychnia or morphia as contained in nux vomica or opium, it being frequently stated that some persons, vendors or makers of this common beverage, are in the habit of adding these and other materials in small quantities to their beer to give it a more intoxicating power. I therefore digested some nux vomica in coarse powder with a part of the ale prepared for the previous experiments, and on passing this when cold a great number of times through the charcoal the bitter flavour still remained, and hence I concluded at the time that my hypothesis was correct. Other engagements broke in on my experiments at this time, and prevented my prosecuting the investigation further.

About ten days since, however, I was recalled to this subject by some other experiments, and tried the effect of animal charcoal on the decoctions of some other astringent bitter substances, as oak bark, Peruvian bark (Cinchona cordifolia), and others, all of which had their flavour entirely removed. It may be as well to mention here, that in this second and also in a subsequent series of experiments the animal charcoal was added to the warm solution of

the material under trial, and they were digested together on a sand-bath until the full effect had taken place, after which the fluid was passed through a filter. The charcoal used was the ordinary bone-black of the sugar-refiner, purified by digestion with hydrochloric acid, washed as long as any saline matter was abstracted, and then dried and heated to low redness. I then tested the extent of this extraordinary power of charcoal by submitting a decoction of aloes to its action, with the same results, the whole of the bitter flavour being removed.

I had proceeded thus far when I was referred by my friend Mr. Henry to a work published at Breslau in 1842, by MM. A Duflos and A. Hirsch, entitled Ökonomische Chemie, where, under the article Beer, at page 65, I found nearly all that I had observed described in a few words; namely, that the bitter of the hop, and of all other vegetables used as substitutes for it, as gentian, wormwood, &c., and even aloes, was removed by animal charcoal, but that the bitter of nux vomica, which is often made use of in England, was not affected.

On looking over my experiments, however, my attention was arrested by finding that the decoction of the bark of the Cinchona cordifolia had had the whole of its bitter removed. Now, on the grounds stated in the previous part of this paper regarding the active principle, this should not have been the case. I therefore took a small quantity of disulphate of quina, dissolved it by heat in distilled water, and then added the charcoal, and discovered that the whole of the bitter was removed in less than a minute. A solution of acetate of morphia was also submitted to the action of charcoal with a like result. A watery solution of strychnia was similarly affected, and this made it necessary to repeat my former experiment on nux tomica, which had been made on a cold solution and simply filtering it through the charcoal; it was now digested with the aid of heat, and the whole of its bitter flavour quickly disappeared. The statement of Duflos and Hirsch, on this point, is not therefore entirely correct.

To try the extent to which this abstracting power proceeds, two grains of disulphate of quina were dissolved in two ounces of distilled water, and animal charcoal gradually added in small quantities to the warm solution until the whole of its bitter flavour was removed; it was found that twelve grains of the charcoal had been required to effect this.

It becomes a matter of surprise that this power of animal charcoal has, as far as I am aware, never been observed before, notwithstanding the frequent and extensive employment which is made of this agent in the preparation of the vegetable alkalies, their salts, and a great variety of other substances of an organic nature, for which it is directed to be used for the purposes of discoloration in all our chemical works and Pharmacopœias. Numerous analyses of organic substances, in which it has been employed, will also be open to error on the same grounds.

Before leaving this branch of the subject, I should refer to a paper, and I believe the only one that bears particularly on any of the previous statements, by Dr. Louis Hopff, in the 17th volume of the Journal de Pharmacie, p. 172, "On the property of Charcoal in destroying the bitter flavour of many bodies;" in which he gives a series of comparative trials with wood and animal charcoal at a temperature between 789 and 86° Fahr. on solutions of a specified strength, of the extracts of bitter herbs, woods, roots, barks, leaves, flowers, and fruits.

I annex a few examples from this paper of substances which have formed the subject of experiment in the present communication, as I believe that the great discrepances which will be noticed arise from the charcoal employed by Dr. Hopff not having been well prepared.