in general a substance which, by the nature of its energy, and the arrangement of its molecules, is capable of combining with acids, and of neutralizing them. I have observed, likewise, that we ought to consider azote as approaching by its properties the nature of oxygen, chlorine, iodine, and that, like them, it may acidify a certain class of bodies. But all acidifying substances may, as well as oxygen, when they combine with alkalifying substances in proper proportions, form salifiable bases. Of course, ammonia ought to be considered as a particular alkali, in which azote performs the function of oxygen in the other alkalies. I consider, in the same way, carbon in fatty bodies, and particularly in the margarine of Chevreuil, as performing the function of oxygen in the acids; and I consider it in alcohol as performing the function of oxygen in the oxides. I shall observe, that since the printing of the article in which I treat of hydriodic ether, I have ascertained the density of its vapour, and found that it does not coincide with that given by calculating on the supposition that the ether is a compound of the vapour of absolute alcohol and hydriodic acid. As the same thing holds with hydro-chloric ether, the density of which found by experiment is different from that found by calculating it as a compound of the vapour of absolute alcohol and hydro-chloric acid; it appears to me very probable that the alcohol, which may be considered as composed of equal volumes of the vapour of water and olefiant gas condensed into one volume, changes its nature on combining with the acids. I hope to be able to throw light on this subject in a memoir on vapours, which I propose soon to publish.

1,

ARTICLE VI.

Experiments on Tungsten, and its Combinations with Oxygen, Ammonia, and other Substances, to determine the Accuracy of preceding Researches, and to promote our Knowledge of this Substance. By Professor Bucholz.*

Introduction.

SOME time has elapsed since I formed the resolution of making a set of experiments on tungsten, its oxides, and their combinations, in order to verify the accuracy of preceding researches on this substance, and in order to promote our knowledge of its nature and properties. I was in a situation to make these experiments in consequence of a considerable stock of wolfram and Scheele's tungstic acid with which I was furnished, and for which I have chiefly to thank the goodness of my friend Dr. Haberle. This resolution was

* Translated from Schweigger's Neues Journal für Chemie und Physik, vol. ii. p. 1.

rendered still stronger in consequence of a conversation which I had with the celebrated naturalist Professor Steffens, of Halle, who seemed to doubt the accuracy of the statements respecting the great specific gravity of tungsten. The following dissertation contains my experiments and their results as far as the time I had would allow me to follow them up. The continuation of them will follow.

(A.)

Experiments on the best Method of forming Tungstic Acid, or rather Tungstate of Ammonia.

As my object in these experiments was in the first place, for very obvious reasons, directed towards the reduction of tungsten, and as I wanted to verify the statement of Allen and Aikin that this metal may be fully melted by the application of a violent heat to tungstate of ammonia, on that account my first care was to discover a convenient method of obtaining a sufficient quantity of tungstate of ammonia. It was quite natural to try in the first place Scheele's tungstic acid, composed of oxide of tungsten, potash, and muriatic acid, because I had a considerable stock of it in my possession.

Exper. 1.-With a view to the statement of several chemists, who affirm that in order to form pure tungstate of ammonia it is necessary to separate the pure yellow oxide of tungsten from Scheele's tungstic acid by digestion in nitric acid, I made the following experiment:-Two ounces of the triple compound of tungstic oxide, potash, and muriatic acid, were triturated with eight ounces of pure nitric acid of the specific gravity 1.200; and being put into a glass vessel capable of holding 16 oz. of water, were boiled for six hours, and during that time were frequently agitated. This process was very difficult, because the salt and oxide settling at the bottom of the vessel occasioned a continual knocking of the vapour, and by that means the acid was sputtered about. The oxide obtained by this process was very light yellow, without the least shade of lemon. This entitled me to conclude that the triple salt had not been completely decomposed. To obtain a more complete decomposition, the whole was poured into a porcelain dish, and evaporated on the sand-bath to the consistence of a syrup, being constantly stirred during the whole process by a porcelain spatula. The whole was then diluted with 12 oz. of water, and after remaining at rest for 24 hours, the milky solution was separated from the heavy yellow oxide. This oxide was treated ir the same way again in the porcelain dish with 6 oz. of nitric acid. The oxide obtained in this manner, and three times washed with 45 oz. of water, was considered by me as pure. When dried, and heated to redness, it assumed a light yellow colour, and weighed 13 drams. After several weeks, 90 gr. of the same oxide precipitated from the milky liquid.

With this oxide the following experiment was made.

Exper. 2.-300 gr. of the tungstic oxide which had been heated

to redness, and was of a light lemon-yellow colour, were digested for some time with a warm solution of concentrated caustic ammonia. In about an hour the mixture was raised to the boiling temperature; but I did not by this means obtain a complete solution. The mixture was allowed to remain at rest for some time; and by this means the liquid was separated from the undissolved yellowish-grey oxide, and carefully evaporated in a porcelain bason. By this means I obtained 47 gr. of a pea-coloured, foliated, brilliant mass, easily separated from the porcelain vessel, and possessing a hot bitter taste. It was tungstate of ammonia.

This result was quite contrary to my expectation, and to the assertion of other chemists, according to whom pure tungstic oxide is very easily soluble in ammonia. This required a further examination of the residuum which was insoluble in ammonia.

Exper. 3.-This residuum was treated with 8 oz. of caustic ammonia, in the same manner as above related; after which the liquid part was separated from the solid powder, which still had a very grey appearance. By evaporation the solution deposited only 27 gr. of a salt having the same colour as in the preceding experiment, of a pulverulent appearance, and having a sharp bitter taste.

Exper. 4.-As I conjectured that the tungstic oxide was somewhat deoxidized by the ammonia, and thereby rendered grey, I tried, by exposing it to a red heat, to bring this oxide back to its original state, and to obtain a greater proportion of it dissolved in ammonia. I found that by this treatment the grey oxide again assumed a yellow colour, and amounted now to only 230 gr. With this powder the following experiment was made.

Exper. 5.-100 gr. of the same oxide were mixed with 4 oz. of caustic ammonia, and the mixture was digested for 12 hours in a very moderate heat, being often agitated during the digestion. The liquid part was then allowed to separate from the undissolved portion, and decanted off. This solution by evaporation yielded 55 gr. of a white powder, which had a hot and bitter taste, and possessed the properties of tungstate of ammonia. The yellowish-grey colour of the undissolved residuum showed that even in this case, notwithstanding the very moderate heat of the ammonia, a commencement of deoxidation had taken place.

Exper. 6.-The solid residue of the preceding experiment was treated in the same way once more with 4 oz. of caustic ammonia, and the liquid portion separated from the undissolved powder, which had a light grey colour. This solution, when evaporated, gave 11 gr. of a pea-yellow powder, which was tungstate of ammonia, and possessed the same taste as that obtained in the preceding experiments. I could not in this case determine the quantity of matter that had remained undissolved, because a portion of it had been lost.

The result of these experiments shows us that our tungstic oxide, after being exposed to a red heat, is with difficulty soluble in caustic

ammonia, and that by the action of that alkali it undergoes a partial deoxidizement. I resolved, therefore, to make experiments on the solubility of our oxide in carbonate of ammonia.

Exper. 7.-100 gr. of the oxide rendered yellow in experiment 4th were heated with a mixture of half an ounce of subcarbonate of ammonia and 2 oz. distilled water, and the mixture was frequently agitated. A few air bubbles made their escape. The whole being kept almost boiling hot for two hours, the undissolved powder in this case also became grey.

The clear solution deposited on evaporation 66 gr. of tungstate of ammonia, having a white colour, a sharp and bitter taste, and not effervescing when dropped into muriatic acid; showing that it contained no carbonic acid. The dried residue weighed 48 gr.

Exper. 8.-The 48 gr. of residue in the preceding experiment were kept in a red heat for an hour in contact with the atmosphere. By this treatment it again assumed a light lemon-yellow colour. 35 gr. of it were mixed with half an ounce of subcarbonate of ammonia and 2 oz. of water, and the mixture was agitated for some hours, being kept warm all the time. A lively effervescence took place at first. The whole was then gently boiled for one hour, and the liquid portion separated from the grey oxide by the filter. By evaporating the liquid, 20 gr. of a light reddish-grey powder were obtained, which had a sharp bitter taste. The undissolved grey oxide weighed 18 gr.

From these experiments with subcarbonate of ammonia, we see that there exists the same difficulty of solution, and the same deoxidizement, when tungstic oxide is treated with carbonate of ammonia. But as these experiments, as well as the preceding, with caustic ammonia, contradict those of other chemists, as Scheele, Bergman, Klaproth, Richter, &c. respecting the solubility of tungstic oxide in ammonia, I conceived that further experiments were necessary in order to clear up this discordance.

Exper. 9.-A small portion, therefore, of tungstate of ammonia was converted into yellow oxide of tungsten by digestion in concen. trated muriatic acid, washing it in a sufficient quantity of water, and drying it strongly, but without exposing it to a red heat. 10 gr. of this oxide were mixed with two drams of the solution of caustic ammonia. The whole was dissolved immediately without the assistance of heat. The old observations of preceding chemists were confirmed by this experiment.

Exper. 10.-In order to obtain a larger quantity of tungstic oxide not dried in a red heat, and therefore soluble in ammonia, 3 oz. of Scheele's tungstic acid were kept boiling for an hour in 6 oz. of the same nitric acid which I employed in the preceding experiments in a porcelain dish upon a sand-bath, and during the whole time the mixture was constantly stirred with a porcelain pestle. The whole was then evaporated to dryness in a moderate heat. The oxide obtained by this process was of a full lemon-yellow colour. A portion of this being washed with water, and gently dried, dissolved

immediately in ammonia, with the exception of a very small portion of a light white substance in powder.

This success excited in me the strongest hopes of succeeding in my object by this method, and led me to suspect that in all probability the tungstic oxide had been rendered insoluble in ammonia by exposing it to a red heat. I resolved to prove the truth of this conjecture in the following way.

The tungstic oxide obtained by the preceding process was well washed twice successively, each time with 24 oz. of water, and by that means freed from the saltpetre formed during the process, and from the excess of acid, and obtained in a state of purity. When collected on the filter, and well dried, it weighed 2 oz. 2 dr. The liquid retained a portion of oxide so light, and in a state of such fine division, that it could not be retained upon the filter, but passed through it how many times soever it was filtered. This yellowish milky liquid, being set aside for three months, allowed the oxide gradually to subside. When collected and dried, it weighed 2 dr. 1 gr.

With this oxide, which had a lemon-yellow colour passing into yolk of egg colour, the following experiments were made, in order to determine its solubility in caustic ammonia.

Exper. 11.-Two ounces of pure caustic ammonia, of the strength which it has when prepared according to the formula given by me in the Almanac for Chemists and Apothecaries of 1803, p. 20, were put in contact with the whole of our dry tungstic oxide. 1 oz. and 20 gr. dissolved in the ammonia, or were at least converted into a white pulverulent matter.

From the phenomena it was evident that a much greater proportion of the oxide would have dissolved, or been converted into a white powder, by the quantity of ammonia employed, more probably than all that I had in my possession. I determined, therefore, to ascertain in another experiment upon a smaller scale the capacity of ammonia in dissolving tungstic oxide, or converting it into a white powder.

In the mean time I separated by the filter the white, light, slimy matter, which existed in the ammoniacal solution. It was washed on the filter with 14 oz. of caustic ammonia, and then dried. Its weight amounted to 80 gr. It exhibited the properties of a quadruple compound of ammonia, potash, tungstic oxide, and muriatic acid, with some oxide of iron and silica from which the tungstic oxide had not been freed. The ammoniacal solution was evaporated to dryness in a porcelain vessel. 300 gr, of tungstate of ammonia were obtained, though by an unlucky accident a third part of the solution had been lost.

Exper. 12.-50 gr. of a solution of caustic ammonia were brought in contact with 80 gr. of oxide of tungsten. The mixture became stiff; and it was with difficulty that some remains of the yellow oxide could be perceived mixed with the white mass. By agitation in a considerable quantity of water, and still better by the