IN

'N the Bakerian lecture, which I had the honor of reading before the Society, November 19, 1807, I mentioned that in heating potassium strongly in ammonia, I found that there was a considerable increase of volume of the gas, that hydrogene and nitrogene were produced, and that the potassium appeared to be oxidated; but this experiment, as I had not been able to examine the residuum with accuracy, I did not publish. I stated it as an evidence, which I intended to pursue more fully, of the existence of oxygene in ammonia.

In a paper read before the Royal Society last June, which they have done me the honor of printing, I have given an account of various experiments on the amalgam from ammonia, discovered by Messrs. Berzelius and Pontin, and in a note attached to this communication, I ventured to controvert an opinion of M. M. Gay Lussac and Thenard, with respect to the agency of potassium and ammonia, even on their own statement of facts, as detailed in the Moniteur for May 27, 1808. The general obscurity belonging to these refined objects of research, their importance and connexion

with the whole of chemical theory, have induced me, since that time, to apply to them no inconsiderable degree of labour and attention; and the results of my inquiries will, I trust, be found not only to confirm my former conclusions; but likewise to offer some novel views.

In the first of these series of operations on the action of potassium on ammonia, I used retorts of green glass; I, then suspecting oxygene might be derived from the metallic oxides in the green glass, employed retorts of plate glass, and last of all, I fastened the potassium upon trays of platina, or iron, which were introduced into the glass retorts, furnished with stop cocks. These retorts were exhausted by an excellent air-pump, they were filled with hydrogene, exhausted a second time, and then filled with ammonia from an appropriate mercurial gas-holder. In this way the gas was operated upon in a high degree of purity, which was always ascertained; and all the operations performed out of the contact of mercury, water, or any substances that could interfere with the results.

I at first employed potassium pro

cured

eured by electricity; but I soon substituted for it the metal obtained by the action of ignited iron upon potash, in the happy method discovered by M. M. Gay Lussac and Thenard, finding that it gave the same results, and could be obtained of a uniform quality, and in infinitely larger quantities, and with much less labor and expense.

When ammonia is brought in contact with about twice its weight of potassium at common temperatures, the metal loses its lustre, and becomes white, there is a slight diminution in the volume of the gas; but no other effects are produced. The white crust examined proves to be potash, and the ammonia is found to contain a small quantity of hydrogene, usually not more than equal in volume to the metal. On heating the potassium in the gas, by means of a spirit lamp applied to the bottom of the retort, the color of the crust is seen to change from white to a bright azure, and this gradually passes through shades of bright blue and green into dark olive. The crust and the metal then fuse together; there is a considerable effervescence, and the crust passing off to the sides, suffers the brilliant surface of the potassium to appear. When the potassium is cooled in this state it is again covered with the white crust. By heating a second time it swells considerably, becomes porous, and appears crystallized, and of a beautiful azure tint; the same series of phenomena, as those before described, occur in a continuation of the process, and it is finally entirely converted into the dark olive coloured substance.

In this operation, as has been stated by M. M. Gay Lussac and Thenard, a gas, which gives the

same diminution by detonation with oxygene, as hydrogene is evolved, and ammonia disappears.

The proportion of the ammonia which loses its elastic form, as I have found by numerous trials, varies according as the gas em ployed contains more or less moisture.

Thus eight grains of potassium, during its conversion into the olive coloured substance, in ammonia saturated with water at 63° Fabrenheit, and under a pressure equal to that of 29.8 inches of mercury, had caused the disappearance of twelve cubical inches and a half of ammonia;

but the same quantity of metal acted upon under similar circumstances, except that the am monia had been deprived of as much moisture as possible by ex. posure for two days to potash that had been ignited, occasioned a disappearance of sixteen cubical inches of the volatile alkali:

Whatever be the degree of moisture of the gas, the quantities of inflammable gas generated have always appeared to me to be equal for equal qualities of metal. M. M. Gay Lussac and Thenard are said to have stated, that the proportions in their experiment were the same as would have resulted from the action of water upon potas. sium. In my trials they have been rather less. Thus, in an experiment conducted with every possible attention to accuracy of manipula. tion, eight grains of potassium generated, by their operation upon water, eight cubical inches and a half of hydrogene gas; and eight grains from the same mass, by their action upon ammonia, produced eight cubical inches and one eighth of inflammable gas. This difference is inconsiderable, yet I have always found it to exist, even in cases

where

where the ammonia has beeningreat excess, and every part of the metal apparently converted into the olive coloured substance.

No other account of the experiments of M. M. Gay Lussac and Thenard has, I believe, as yet been received in this country, except that in the Moniteur already referred to; and in this no mention is made of the properties of the substance produced by the action of ammonia on potassium. Having examined them minutely and found them curious, I shall generally describe them.

1. It is crystallized and presents irregular facets, which are ex tremely dark, and in colour and Justre not unlike the protoxide of iron; it is opaque when examined in large masses, but it is semi-transparent in the films, and appears of a bright brown colour by transmitted light.

2. It is fusible at a heat a little above that of boiling water, and if heated much higher, emits globules of gas.

3. It appears to be considerably heavier than water, for it sinks rapidly in oil of sassafras.

4. It is a non-conductor of electricity

5. When it is melted in oxygene gas, it burns with great vividness, emitting bright sparks. Oxygene is absorbed, nitrogene is emitted, and potash, which from its great fusibility seems to contain water, is formed.

6. When brought in contact with water, it acts upon it with much energy, produces heat, and often inflammation, and evolves ammonia. When thrown upon water, it disappears with a hissing noise, and globules from it often move in a state of ignition upon the surface of the water. It rapidly

effervesces and deliquesces in air, but can be preserved under naphtha, in which, however, it softens slowly, and seems partially to dissolve. When it is plunged under water filling an inverted jar, by means of a proper tube, it disappears instantly with effervescence, and the non-absorbable elastic fluid liberated is found to be hydrogene gas.

By far the greatest part of the ponderable matter of the ammonia that disappears in the experiment of its action upon potassium, evidently exists in the dark fusible product. On weighing a tray containing six grains of potassium, before and after the process, the volatile alkali employed having been very dry, I found that it had increased more than two grains; the rapidity with which the product acts upon moisture, prevented me from determining the point with great minuteness; but I doubt not, that the weight of the olive colored substance, and of the hydrogene disengaged, pecisely equals the weight of the potassium and ammonia consumed.

M. M. Gay Lussac and Thenard are said to have procured from the fusible substance, by the applica. tion of a strong heat, two fifths of the quantity of ammonia that had disappeared in the first process, and a quantity of hydrogene and nitrogene, in the proportions in which they exist in ammonia, equal fo one fifth more.

My results have been very different, and the reasons will, I trust, be immediately obvious.

When the retort containing the fusible substance is exhausted, filled with hydrogene, and exhausted a second time, and heat gradually applied, the substance soon fuses, effervesces, and, as the heat in

ereases,

creases, gives off a considerable quantity of elastic fluid, and becomes at length, when the tem perature approaches nearly to dull redness, a dark grey solid, which, hy a continuance of this degree of heat, does not undergo any alteration.

In an experiment, in which eight grains of potassium had absorbed Eixteen cubical inches of well dried ammonia in a glass retort, the fusible substance gave of twelve cubical inches and a half of gas, by being heated nearly to redness, and this gas analysed, was found to consist of three quarters of a cubical inch of ammonia, and the remainder of elastic fluids, which, when mixed with oxygene gas in the proportion of 6 to 0, and acted upon by the electric spark, diminished to 5. The temperature of the atmosphere, in this process, was 57° Fahrenheit, and the pressure equalled that of 30.1 inches of mercury.

In a similar experiment, in which the platina-tray containing the fusible substance was heated in a polished iron tube, filled with hydrogene gas, and connected with a pneumatic apparatus containing very dry mercury, the quantity of elastic fluid given off, all the corrections being made, equalled thirteen cubical inches and three quarters, and of these a cubical inch was ammonia; and the residual gas, and the gas introduced into the tube being accounted for, it appeared that the elastic fluid generated, destructible by detonation with oxygene, was to be inde structible elastic fluid, as 2.5 to 1.

In this process, the heat applied pproached to the dull red heat. The mercury in the thermometer, s'ood at 02° Fahrenheit, and that in the barometer at 30.3 inches.

In various experiments on different quantities of the fusible substance, in some of which the heat was ap plied to the tray in the green glass retort, and in others, after it had been introduced into the iron tube, and in which the temperature was sometimes raised slowly and sometimes quickly, the comparative results were so near these that I have detailed, as to render any statement of them superfluous.

A little more ammonia, and rather a larger proportion of inflammable gas, were in all instances evolved when the iron tube was used, which I am inclined to attribute to the following circumstances. When the tray was brought through the atmosphere to be introduced into the iron tube, the fusible substance absorbed a small quantity of moisture from the air which is connected with the production of ammonia. And in the process of heating in the retort, the green glass was blackened, and I found that it contained a very small quantity of the oxides of lead and iron, which must have caused the disappearance of the small quantity of hydrogene.

M. M. Gay Lussac and Thenard, it appears from the statement, had brought the fusible substance in contact with mercury, which must have given to it some moisture; and whenever this is the case, it furnishes by heat variable quantities of ammonia. In one instance, in which I heated the fusible substance from nine grains of potas sium, in a retort that had been filled with mercury in its common state of dryness, I obtained seven cubical inches of ammonia as the first product; and in another experiment which had been made with eight grains, and in which moisture was purposely introduced,

I obtained nearly nine cubical inches of ammonia, and only four of the mixed gases.

I am inclined to believe, that if moisture could be introduced only in the proper proportion, the quantity of ammonia generated, would be exactly equal to that which disappeared in the first process.

This idea is confirmed by the trials which I have made, by heating the fusible substance with potash,containing its water of chrystallization, and muriate of lime par-tially dried.

In both these cases, ammonia was generated with great rapidity, and no other gas, but a minute quantity of inflammable gas, evolved, which was condensed by detonation with oxygene with the same phenomena as pure hydrogene.

In one instance, in which thirteen cubical inches of ammonia had disappeared, I obtained nearly eleven and three quarters by the agency of the water of the potash; the quantity of inflammable gas generated, was less than four tenths of a cubical inch.

In another, in which fourteen cubical inches had been absorbed, I procured by the operation of the moisture of muriate of lime, nearly eleven cubical inches of volatile alkali, and half a cubical inch of inflammable gas; and the differences, there is every reason to believe, were owing to an excess of water in the salts, by which some of the gas was absorbed.

Whenever, in experiments on the fusible substance, it has been procured from ammonia saturated with moisture, I have always found that more ammonia is generated from it by mere heat; and the general tenour of the experiments incline me to believe, that the small quantity, produced in experiments 1809.

performed in vacuo, is owing to the small quantity of moisture furnished by the hydrogene gas introduced, and that the fusible substance, heated out of the presence of moisture, is incapable of producing volatile alkali.

MM. Gay Lussac, and Thenard, it is stated, after having obtained three fifths of the ammonia or its elements that had disappeared in their experiment, by heating the product; procured the remaining two fifths, by adding water to the residuum, which after this operation was found to be potash. No notice is taken of the properties of this residuum, which as the details scem to relate to a single experiment, probably was not examined; nor as moisture was present at the beginning of their operations could any accurate knowledge of its náture have been gained.

I have made the residuum of the fusible substance after it has been exposed to a dull red heat, out of the contact of moisture, an object of particular study, and I shall detail its general properties.

It was examined under naptha, as it is instantly destroyed by the contact of air.

1. Its colour is black, and its lustre not much inferior to that of plumbago.

2. It is opaque even in the thinnest films.

3. It is very brittle, and affords a deep gray powder.

4. It is a conductor of elec tricity.

5. It does not fuse at a low red heat, and when raised to this tem perature, in contact with plate glass, it blackens the glass, and a grayish sublimate rises from it, which likewise blackens the glass.

6. When exposed to air at com. mon temperatures, it usually takes

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fire