Chapter III: Part 3

This gas extinguished flame, gave no diminution with oxygene, and the slightest possible with nitrous gas. When an electric spark was passed through it, mingled with oxygene; no inflammation, or _perceptible_ diminution took place.[84] We may consequently conclude that it was nitrogene, mingled with a minute portion of common air, expelled from the water.

[84] The gas was examined by those tests in order to prove that no water had been decomposed.

The charcoal was diminished in bulk to one half nearly, but the loss of weight could not be ascertained, as its pores were filled with mercury.

Now 5 cubic inches of nitrous oxide were absorbed by the water, consequently 5 were decompounded by the charcoal; and these produced 5,1 cubic inches of nitrogene; and by giving their oxygene to the charcoal, apparently 2,4 of carbonic acid.

But 5 cubic inches of nitrous oxide weigh 2,5 grains, and 5,1 cubic inches of nitrogene 1,55; then 2,5-1,55 =,95.

So that reasoning from the relative specific gravities of nitrogene and nitrous oxide, 2,5 grains of the last are composed of 1,55 nitrogene, and,95 oxygene.

But from many experiments made on the specific gravity of carbonic acid, in August, 1799, I concluded that 100 cubic inches of it weighed 47,5 grains, thermometer being 60,1°, and barometer 29,5. Consequently, making the necessary corrections, 2,4 cubic inches of it weigh 1,14 grains; and on Lavoisier’s and Guyton’s[85] estimation of its composition, these 1,13 grains contain 8,2 of oxygene.

[85] See the curious paper of this excellent philosopher, on the combustion of the diamond, in which he proves that charcoal is, in fact, oxide of diamond. Annales de Chimie, xxxi.

So that, drawing conclusions from the quantity of carbonic acid formed in this experiment, 2,5 grains of nitrous oxide will be composed of,82 oxygene, and 1,68 nitrogene.

The difference between these estimations is considerable, and yet not more than might have been expected, if we consider the probable sources of error in the experiment.

1. It is likely that variable minute quantities of hydrogene remain combined with charcoal, even after it has been long exposed to a red heat.

2. It is probable that the nitrogene and carbonic acid produced were capable of dissolving more water than that held in solution by the nitrous oxide; and if so, they were more condensed than if saturated with moisture, and hence the quantity of carbonic acid under-rated.

We may consequently suppose the estimation founded on the quantity of nitrogene evolved, most correct; and making a small allowance for the difference, conclude, that 100 grains of nitrous oxide are composed of about 37 oxygene, and 63 nitrogene; existing in a much more condensed state than when in their simple forms.

The tolerable accuracy of this statement will be hereafter demonstrated by a number of experiments on the combustion of different bodies in nitrous oxide, detailed in Research II.

VI. _Minute examination of the decomposition of Nitrate of Ammoniac._

Into a retort weighing 413,75 grains, and of the capacity of 7,5 cubic inches, 100 grains of pulverised compact nitrate of ammoniac were introduced. To the neck of this retort was adapted a recipient, weighing 711 grains, tubulated for the purpose of communicating with the mercurial airholder, and of the capacity of 8,3 cubic inches.

Temperature being 50° and atmospheric pressure 30,6, the recipient was inserted into a vessel of cold water, and made to communicate with the airholder. The heat of a spirit lamp was then slowly applied to the retort: the salt quickly began to decompose, and to liquify. The temperature was so regulated, as to keep up an equable and slow decomposition.

During this decomposition, no luminous appearance was perceived in the retort; the gas that came into the airholder was very little clouded, and much water condensed in the receiver.

After the process was finished, the communication between the mercurial airholder and the recipient was preserved till the common temperature was restored to the retort.

The volume of the gas in the cylinder was 85,5 cubic inches. The absolute quantity of nitrous oxide in those 85,5 cubic inches, it was difficult to ascertain with great nicety, on account of the common air previously contained in the vessels.

45 measures of it, exposed to well boiled water, diminished by agitation to 8 measures. So that reasoning from the quantity of air, which should have been expelled from the water by the nitrous oxide, we may conclude that the 85,5 cubic inches were nearly pure.

The retort now weighed 419,25 grains, consequently 5,5 grains of salt remained in it. This salt was chiefly collected about the lower part of the neck, and contained rather more water than the compact nitrate, as in some places it was crystalised.

The recipient with the fluid it contained, weighed 759 grains. It had consequently gained in weight 48 grains.

Now the 85,5 cubic inches of nitrous oxide produced, weigh about 42,5 grains; and this added to 48 and 5,5, = 96 grains; so that about 4 grains of salt and fluid were lost, probably by being carried over and deposited by the gas.[86]

[86] This was actually the case; for on examining the conducting tube the day after the experiment, some minute crystals of prismatic nitrate of ammoniac were perceived in it.

As much of the fluid as could be taken out of the recipient, weighed 46 grains, and held in solution much nitrate of ammoniac with superabundance of acid. This acid required for its saturation, 3⅛ of carbonate of ammoniac (containing, as well as I could guess), about 20 per cent alkali.

The whole solution evaporated, gave 18 grains of compact nitrate of ammoniac. But reasoning from the quantity of carbonate of ammoniac employed, the free nitric acid was equal to 2,75 grains, and this must have formed 3,56 grains of salt. Consequently the salt pre-existing in the solution was about 14,44 grains.

But besides the fluid taken out of the recipient, 2 grains remained in it: let us suppose this, and the 4 grains lost, to contain 2 of salt, and,6 of free acid.

Then the undecompounded

salt is 5,5 + 14,4 + 2 = 21,9
The free acid 2,75 + ,6 = 3,35
Gas 42,5
Water 32,25
——————
100

Now about 78,1 grains of salt were decompounded, and formed into 42,5 grains of gas, 3,35 grains acid, and 32,25 grains water.

But there is every reason to suppose, that in this process, when the hydrogene of the ammoniac combines with a portion of the oxygene of the nitric acid to form water, and the nitrogene enters into union with the nitrogene and remaining oxygene of the nitric acid, to form nitrous oxide; that water pre-existing in nitric acid and ammoniac, such as they existed in the aëriform state, is deposited with the water produced by the new arrangement, and not wholly combined with the nitrous oxide formed. Hence it is impossible to determine with great exactness, the quantity of water which was absolutely formed in this experiment.

78,1 grains of salt are composed of 15,4 alkali, 58 acid, and 4,7 water.

And reasoning from the different affinities of water for nitric acid, ammoniac, and nitrous oxide, it is probable that ammoniac, in its decomposition, divides its water in such a ratio, between the nitrogene furnished to the nitrous oxide, and the hydrogene entering into union with the oxygene of the nitric acid, as to enable us to assume, that the hydrogene requires for its saturation nearly the same quantity of oxygene as when in the aëriform state; or that it certainly cannot require less.

But 15,4 alkali contain 3,08 hydrogene, and 12,32 nitrogene;[87] and 3,08 hydrogene require 17,4 of oxygene to form 20,48 of water.

[87] Owing part of their weight to an unknown quantity of water.

Now 32,5 grains of water existed before the experiment; 4,7 grains of water were contained by the salt decomposed, and 32,5-4,7 = 27,8: and 27,8-20,48, the quantity generated, = 7,52, the quantity existing in the nitric acid.

But the nitric acid decomposed is 58ᵍ-3,35 = to 54,7; and 54,7-7,5 = 47,2, which entered into new combinations. These 47,2 consist of 33,2 oxygene, and 14, nitrogene. And 33,2-17,4, the quantity employed to form the water, = 15,8, which combined with 14,0, nitrogene of the nitric acid, and 12,32 of that of the ammoniac, to form 42,12 of nitrous oxide. And on this estimation, 100 parts of nitrous oxide would contain 37,6 oxygene, and 62,4 nitrogene; a computation much nearer the results of the analysis than could have been expected, particularly as so many unavoidable sources of error existed in the process.

The experiment that I have detailed is the most accurate of four, made on the same quantity of salt. The others were carried on at rather higher temperatures, in consequence of which, more water and salt were sublimed with the gas.

To Berthollet, we owe the discovery of the products evolved during the slow decomposition of nitrate of ammoniac; but as this philosopher in his examination of this process, chiefly designed to prove the existence of hydrogene in ammoniac, he did not ascertain the quantity of gas produced, or minutely examine its properties; from two of them, its absorption by water and its capability of supporting the vivid combustion of a taper, he inferred its identity with the dephlogisticated nitrous gas of Priestley, and concluded that it was nitrous gas with excess of pure air.[88]

[88] Mem. de Paris. 1785, and Journal de Physique, 1786, page 175.

VII. _Of the heat produced during the decomposition of nitrate of ammoniac._

To ascertain whether the temperature of nitrate of ammoniac was increased or diminished after it had been raised to the point essential to its decomposition, during the evolution of nitrous oxide and water; that is, in common language, whether heat was generated or absorbed in the process; I introduced a thermometer into about 1500 grains of fibrous nitrate of ammoniac, rendered liquid in a deep porcelain cup. During the whole of the evaporation, the temperature was about 380°, the fire being carefully regulated.

As soon as the decomposition took place, the thermometer began to rise; in less than a quarter of a minute it was 410°, in two minutes it was 460°.

The cup was removed from the fire; the decomposition still went on rapidly, and for about a minute the thermometer was stationary. It then gradually and slowly fell; in three minutes it was 440°, in five minutes 420°, in seven minutes 405° in nine minutes 360° and in thirteen minutes 307°, when the decomposition had nearly ceased, and the salt began to solidify.

From this experiment, it is evident that an increase of temperature is produced by the decomposition of nitrate of ammoniac: though the capacity of water and nitrous oxide for heat, supposing the truth of the common doctrine, and reasoning from analogy, must be considerably greater than that of the salt.

VIII. _Of the decomposition of Nitrate of Ammoniac at high temperatures, and production of Nitrous gas, Nitrogene, Nitrous Acid, and Water._

At an early period of my investigation relating to the nitrous oxide, I discovered that when a heat above 600° was applied to nitrate of ammoniac, so that a vivid luminous appearance was produced in the retort, certain portions of nitrous gas, and nitrogene, were evolved with the nitrous oxide. But I was for some time ignorant of the precise nature of this decomposition, and doubtful with regard to the possibility of effecting it in such a manner as to prevent the production of nitrous oxide altogether.

I first attempted to decompose nitrate of ammoniac at high temperatures, by introducing it into a well coated green glass retort, having a wide neck, communicating with the pneumatic apparatus, and strongly heated in an air-furnace. But though in this process a detonation always took place, and much light was produced, yet still the greater portion of the gas generated was nitrous oxide; the nitrous gas and nitrogene never amounting to more than one third of the whole.

After breaking many retorts by explosions, without gaining any accurate results, I employed a porcelain tube, curved so as to be capable of introduction into the pneumatic apparatus, and closed at one end.

The closed end was heated red, nitrate of ammoniac introduced into it, and all the latter portions of gas produced in the explosion, received in the pneumatic apparatus, filled with warm water.

Three explosions were required to fill a jar of the capacity of 20 cubic inches. The gas produced in the first, when it came over, was transparent and dark orange, similar in its appearance to the nitrous acid gas produced in the first experiment; but it speedily became white and clouded, whilst a slight diminution of volume took place.

When the second portion was generated and mingled with the clouded gas, it again became transparent and yellow for a short time, and then assumed the same appearance as before.

The water in the trough, after this experiment, had an acid taste, and quickly reddened cabbage juice rendered green by an alkali.

6 cubic inches of the gas produced were exposed to boiled water, but little or no absorption took place. Hence, evidently, it contained no nitrous oxide.

They were then exposed to solution of sulphate of iron: the solution quickly became dark colored, and an absorption of 1,6 took place on agitation.[89]

[89] The absorption of nitrous gas by sulphate of iron, &c. will be treated of in the next division.

The gas remaining instantly extinguished the taper, and was consequently nitrogene.

This experiment was repeated, with nearly the same results.

We may then conclude, that at high temperatures, nitrate of ammoniac is wholly resolved into water, nitrous acid, nitrous gas, and nitrogene; whilst a vivid luminous appearance is produced.

The transparency and orange color produced in the gas that had been clouded, by new portions of it, doubtless arose from the solution of the nitric acid and water forming the cloud, in the heated nitrous vapor produced, so as to constitute an aëriform triple compound; whilst the cloudiness and absorption subsequent were produced by the diminished temperature, which destroyed the ternary combination, and separated the nitrous acid and water from the nitrous gas.

From the rapidity with which the deflagration of nitrate of ammoniac proceeds, and from the immense quantity of light produced, it is reasonable to suppose that a very great increase of temperature takes place. The tube in which the decomposition has been effected, is always ignited after the process.

IX. _Speculations on the decompositions of Nitrate of Ammoniac._

All the phænomena of chemistry concur in proving, that the affinity of one body, A, for another, B, is not destroyed by its combination with a third, C, but only modified; either by condensation, or expansion, or by the attraction of C for B.

On this principle, the attraction of compound bodies for each other must be resolved into the reciprocal attractions of their constituents, and consequently the changes produced in them by variations of temperature explained, from the alterations produced in the attractions of those constituents.

Thus in nitrate of ammoniac, four affinities may be supposed to exist:

1. That of hydrogene for nitrogene, producing ammoniac.

2. That of oxygene for nitrous gas, producing nitric acid.

3. That of the hydrogene of ammoniac for the oxygene
of nitric acid.

4. That of the nitrogene of ammoniac for the nitrous gas
of nitric acid.

At temperatures below 300°, the salt, from the equilibrium between these affinities, preserves its existence.

Now when its temperature is raised to 400°, the attractions of hydrogene for nitrogene,[90] and of nitrous gas for oxygene,[91] are diminished; whilst the attraction of hydrogene for oxygene[92] is increased; and perhaps that of nitrogene for nitrous gas.

[90] As is evident from the decomposition of ammoniac by heat.

[91] Nitric acid is phlogisticated by heat, as appears from Dr. Priestley’s experiments. Vol. 3, p. 26.

[92] As is evident from the increase of temperature required for the formation of water.

Hence the former equilibrium of affinity is destroyed, and a new one produced.

The hydrogene of the ammoniac combines with the oxygene of the nitric acid to generate water; and the nitrogene of the ammoniac enters into combination with the nitrous gas to form nitrous oxide: and the water and nitrous oxide produced, most probably exist in binary combination in the aëriform state, at the temperature of the decomposition.

But when a heat above 800° is applied to nitrate of ammoniac, the attractions of nitrogene and hydrogene for each other, and of oxygene for nitrous gas,[93] are still more diminished; whilst that of nitrogene for nitrous gas is destroyed, and that of hydrogene for oxygene increased to a great extent: likewise a new attraction takes place; that of nitrous gas for nitric acid, to form nitrous vapor.[94] Hence a new arrangement of principles is rapidly produced; the nitrogene of ammoniac having no affinity for any of the single principles at this temperature, enters into no binary compound: the oxygene of the nitric acid forms water with the hydrogene, and the nitrous gas combines with the nitric acid to form nitrous vapor. All these substances most probably exist in combination at the temperature of their production; and at a lower temperature, assume the forms of nitrous acid, nitrous gas, nitrogene, and water.

[93] For ammoniac and nitrous oxide are both decomposed at the red heat, and oxygene given out from nitric acid when it is passed through a heated tube.

[94] Whenever nitrous acid is produced at high temperatures, it is always highly phlogisticated, provided it has not been long in contact with oxygene. When Dr. Priestley passed nitric acid through a tube heated red, he procured much oxygene, and phlogisticated acid; and the water in the apparatus employed was fully impregnated with nitrous air. Hence it would appear, that heat diminishes the attraction between oxygene and nitrous gas, and increases the affinity of nitrous gas for nitrous acid. Mr. JAMES THOMSON, whose theory of the Nitrous Acid I have already mentioned, from some experiments on the phlogistication of Nitric Acid by heat, which he has communicated to me, concludes with great justness, that a portion of the acid is always completely decomposed in this process: the oxygene liberated, and the nitrous gas combined with the remaining acid.

I have avoided entering into any discussions concerning the light and heat produced in this process; because these phænomena cannot be reasoned upon as isolated facts, and their relation to general theory will be treated of hereafter.

X. _On the preparation of Nitrous Oxide for experiments on Respiration._

When compact nitrate of ammoniac is slowly decomposed, the nitrous oxide produced is almost immediately fit for respiration; but as one part of the salt begins to decompose before the other is rendered fluid, a considerable loss is produced by sublimation.

For the production of large quantities of nitrous oxide, fibrous nitrate of ammoniac should be employed. This salt undergoes no decomposition till the greater part of its water is evaporated, and in consequence at the commencement of that process, is uniformly heated.

The gas produced from fibrous nitrate, must be suffered to rest at least for an hour after its generation. At the end of this time it is generally fit for respiration. If examined before, it will be found to contain more or less of a white vapor, which has a disagreeable acidulous taste, and strongly irritates the fauces and lungs. This vapor, most probably, consists of acid nitrate of ammoniac and water, which were dissolved by the gas at the temperature of its production, and afterwards slowly precipitated.

It is found in less quantity when compact nitrate is employed, because more salt is sublimed in this process, which being rapidly precipitated, carries with it the acid and water.

Whatever salt is employed, the last portions of gas produced, generally contain less vapor, and may in consequence be respired sooner than the first.

The nitrate of ammoniac should never be decomposed in a metallic vessel,[95] nor the gas produced suffered to come in contact with any metallic surface; for in this case the free nitric acid will be decomposed, and in consequence, a certain quantity of nitrous gas produced.

[95] Except it be gold or platina.

The apparatus that has been generally employed in the medical pneumatic institution, for the production of nitrous oxide, consists

1. Of a glass retort, of the capacity of two or three quarts,
orificed at the top, and furnished with a ground stopper.

2. Of a glass tube, conical for the purpose of receiving the
neck of the retort; about ,4 inches wide in the narrowest
part, 4 feet long, curved at the extremity, so as to be
capable of introduction into an airholder, and inclosed by
tin plate to preserve it from injury.

3. Of airholders of Mr. Watt’s invention, filled with water
saturated with nitrous oxide.

4. Of a common air-furnace, provided with dampers for the
regulation of the heat.

The retort, after the insertion of the salt, is connected with the tube, carefully luted, and exposed to the heat of the furnace, on a convenient stand. The temperature is never suffered to be above 500°. After the decomposition has proceeded for about a minute, so that the gas evolved from the tube enlarges the flame of a taper, the curved end is inserted into the airholder, and the nitrous oxide preserved.

The water thrown out of the airholders in consequence of the introduction of the gas, is preserved in a vessel adapted for the purpose, and employed to fill them again; for if common water was to be employed in every experiment, a great loss of gas would be produced from absorption.

A pound of fibrous nitrate of ammoniac, decomposed at a heat not above 500°, produces nearly 5 cubic feet of gas; whilst from a pound of compact nitrate of ammoniac, rarely more than 4,25 cubic feet can be collected.

For the production of nitrous oxide in quantities not exceeding 20 quarts, a mode still more simple than that I have just described may be employed. The salt may be decomposed by the heat of an argands lamp, or a common fire, in a tubulated glass retort, of 20 or 30 cubic inches in capacity, furnished with a long neck, curved at the extremity; and the gas received in small airholders.

Thus, if the pleasurable effects, or medical properties of the nitrous oxide, should ever make it an article of general request, it may be procured with much less time, labor, and expence,[96] than most of the luxuries, or even necessaries, of life.

[96] A pound of nitrate of ammoniac costs about 5s. 10d. This pound, properly decomposed, produces rather more than 34 moderate doses of air; so that the expence of a dose is about 2d. What fluid stimulus can be procured at so cheap a rate?

DIVISION IV.

_EXPERIMENTS and OBSERVATIONS on the COMPOSITION of
NITROUS GAS, and on its ABSORPTION by different
bodies._

I. _Preliminaries._

In my account of the composition of nitric acid, in Division I. I gave an estimation of the quantities of oxygene and nitrogene combined in nitrous gas: I shall now detail the experiments on which that estimation is founded.

At an early period of my researches relating to nitrous oxide, from the observation of the phænomena taking place during the production of this substance, I had concluded, that the common opinion with regard to the composition of nitrous gas, was very distant from the truth. I had indeed analysed nitrous gas, by converting it into nitrous oxide, before I attempted to ascertain its composition by immediately separating the constituent principles from each other: and my first hopes of the possibility of effecting this, were derived from Dr. Priestley’s experiments on the combustion of pyrophorus in nitrous gas, and on the changes effected in it, by heated iron and charcoal.

This great philosopher found, that pyrophorus placed in contact with nitrous gas, burnt with great vividness, whilst the gas was diminished in volume to about one half, which generally consisted of nitrogene and nitrous oxide. He likewise found, iron heated by a lens in nitrous gas, increased in weight, whilst the gas was diminished about ½, and converted into nitrogene.[97]

He heated common charcoal, and charcoal of copper,[98] in nitrous gas by a lens. When common charcoal was employed, the gas was neither increased or diminished in bulk, but wholly converted into nitrogene; when charcoal of copper was used, the volume was a little increased, and the gas remaining consisted of ⁵/₇ nitrogene, and ²/₇ carbonic acid.

[97] Experiments and Observations, vol. II. pag. 50. Last Edition.

[98] That is, charcoal produced by the decomposition of spirits of wine. Vol. II. pag. 39.

In his experiments on the iron and pyrophyrus, the nitrous gas was evidently decomposed. From the great quantity of nitrogene produced in those on the charcoal, it seems likely that both the common charcoal,[99] and the charcoal of copper employed contained atmospherical air, which being dispelled by the heat of the lens, was decomposed by the nitrous gas: indeed, till I made the following experiment, I suspected that the carbonic acid produced, when the charcoal of copper was employed, arose from a decomposition of the nitrous acid, formed in this way.

[99] Dr. Priestley says, “having heated iron in nitrous air, I proceeded to heat in the same air, a piece of charcoal not long after it had been subjected to a strong heat covered with sand. The sun not shining immediately, after the charcoal was introduced into the vessel of air, through the mercury by which it was confined, part of the air was absorbed; but on heating the charcoal, the quantity was increased. Having continued the progress as long as I thought necessary, I examined the air and found it to be about as much as the original quantity of nitrous air; but it was all phlogisticated air extinguishing a candle and having no mixture of fixed air in it.”—Experiments and Observations, Vol. II, page 39.

I introduced a piece of well-burnt charcoal, which could hardly have weighed the eighth of a grain, whilst red hot, under a cylinder filled with mercury, and admitted to it half a cubic inch of nitrous gas. A slight absorption took place.

The sun being very bright, I kept the charcoal in the focus of a small lens for near a quarter of an hour. At the end of this time the gas occupied a space nearly as before the experiment, and a very minute portion of the charcoal had been consumed. On introducing into the cylinder a small quantity of solution of strontian, a white precipitation was perceived, and the gas slowly diminished to about three tenths of a cubic inch. To these three tenths a little common air was admitted, when very slight red fumes were perceived.

This experiment convinced me, that the attraction of charcoal for the oxygene of nitrous gas, at high temperatures, was sufficiently strong to effect a slow decomposition of it.

To be more accurately acquainted with this decomposition, and to learn the quantities of carbonic acid and nitrogene produced from a known quantity of nitrous gas, I proceeded in the following manner.

II. _Analysis of Nitrous Gas by Charcoal._

A quantity of nitrous gas was procured in a water apparatus, from the decomposition of nitrous acid by mercury. A portion of it was transferred to the mercurial trough. After the mercury and the jar had been dried by bibulous paper, 40 measures of this portion were agitated in a solution of sulphate of iron. The gas remaining after the absorption was complete, filled about a measure and half; so that the nitrous gas contained nearly ¹/₂₆ nitrogene.

Thermometer being 53°, a small piece of well-burnt charcoal, the weight of which could hardly have equalled a quarter of a grain, was introduced ignited, into a small cylinder filled with mercury, graduated to,10 grain measures; to this, 16 measures, equal to 160 grain m. of nitrous gas, were admitted. An absorption of about one measure and half took place. When the focus of a lens was thrown on the charcoal, a slight increase of the gas was produced, from the emission of that which had been absorbed.

After the process had been carried on for about a half an hour, the charcoal evidently began to fume, and to consume very slowly, though no alteration in the volume of the gas was observed.

The sun not constantly shining, the progress of the experiment was now and then stopped: but taking the whole time, the focus could not have been applied to it for less than four hours. When the process was finished, the gas was increased in bulk nearly three quarters of a measure.

A drop of water was introduced into the cylinder, by means of a small glass tube, on the supposition that the carbonic acid, and nitrogene, might be capable of holding in solution, more water than that contained in the nitrous gas decomposed; but no alteration of volume took place.

When 20 grain measures of solution of pale green[100] sulphate of iron were introduced into the cylinder, they became rather yellower than before, but not dark at the edges, as is always the case when nitrous gas is present. On agitation, a diminution of nearly half a measure was produced, doubtless from the absorption of some of the carbonic acid by the solution.

[100] That is, sulphate of iron containing oxide of iron, in the first degree of oxygenation.

A small quantity of caustic potash, much more than was sufficient to decompose the sulphate of iron, was now introduced. A rapid diminution took place, and the gas remaining filled about 8 measures. This gas was agitated for some time over water, but no absorption took place. Two measures of it were then transferred into a detonating cylinder with two measures of oxygene. The electric spark was puffed through them, but no diminution was produced. Hence it was nitrogene, mingled with no ascertainable quantity of hydrogene: consequently little or no water could have been decomposed in the process.

Now supposing, for the greater ease of calculation, each of the measures employed, cubic inches.

16 of nitrous gas—¹/₂₆ = 15,4 were decomposed, and these weigh, making the necessary corrections, 5,2; but 7,4 nitrogene were produced, and these weigh about 2,2. So that reasoning from the relative specific gravities of nitrous gas and nitrogene, 5,2 grains of nitrous gas will be composed of 3 oxygene, and 2,2 nitrogene.

But 8,7 of carbonic acid were produced, which weigh 4,1 grains, and consist of 2,9 oxygene, and 1,2 charcoal.[101] Consequently, drawing conclusions from the quantity of carbonic acid formed, 5,2 grains of nitrous gas will consist of 2,9 oxygene, and 2,3 nitrogene.

[101] That is, carbon, or oxide of diamond.

The difference in these estimations is much less than could have been expected; and taking the mean proportions, it would be inferred from them, that 100 grains of nitrous gas, contain 56,5 oxygene, and 43,5 nitrogene.

I repeated this experiment with results not very different, except that the increase of volume was rather greater, and that more unabsorbable gas remained; which probably depended on the decomposition of a minute quantity of water, that had adhered to the charcoal in passing through the mercury.

As nitrous gas is decomposable into nitrous acid, and nitrogene, by the electric spark; it occurred to me, that a certain quantity of nitrous acid might have been possibly produced, in the experiments on the decomposition of nitrous gas, by the intensely ignited charcoal. To ascertain this circumstance, I introduced into 12 measures of nitrous gas, a small piece of charcoal which had been just reddened. The sun being very bright, the focus of the lens was kept on it for rather more than an hour and quarter. In the middle of the process it began to fume and to sparkle, as if in combustion. In three quarters of an hour, the gas was increased rather more than half a measure; but no alteration of volume took place afterwards.

The mercury was not white on the top as is usually the case when nitrous acid is produced. On introducing into the cylinder a little pale green sulphate of iron, and then adding prussiate of potash, a white precipitate only was produced. Now, if the minutest quantity of nitric acid had been formed, it would have been decomposed by the pale green oxide of iron, and hence, a visible quantity of prussian blue[102] produced, as will be fully explained hereafter.

[102] That is, blue prussiate of iron.

III. _Analysis of Nitrous Gas by Pyrophorus._

I placed some newly made pyrophorus, about as much as would fill a quarter of a cubic inch, in a jar filled with dry mercury, and introduced to it, four cubic inches of nitrous gas, procured from mercury and nitric acid.

It instantly took fire and burnt with great vividness for some moments.

After the combustion had ceased, the gas was diminished about three quarters of a cubic inch. The remainder was not examined; for the diminution appeared to go on for some time, after; in an half hour, when it was compleat, it was to 2 cubic inches. A taper, introduced into these, burnt with an enlarged flame, blue at the edges; from whence it appeared, that they were composed of nitrogene and nitrous oxide.

I now introduced about half a cubic inch of pyrophorus to two cubic inches of nitrous gas; the combustion took place, and the gas was rapidly diminished to one half; and on suffering it to remain five minutes to one third nearly; which extinguished flame.

Suspecting that this great diminution was owing to the absorption of some of the nitrogene formed, by the charcoal of the pyrophorus, I carefully made a quantity of pyrophorus; employing more than two thirds of alumn, to one third of sugar.

To rather more than half of a cubic inch of this, two cubic inches of nitrous gas, which contained about ¹/₄₀ nitrogene, were admitted. After the combustion, the gas remaining, _apparently_ filled a space equal to 1,2 cubic inches; but, as on account of the burnt pyrophyrus in the jar, it was impossible to ascertain the volume with nicety, it was carefully and wholly transferred into another jar. It filled a space equal to 1,15 cubic inches nearly.

When water was admitted to this gas no absorption took place. It underwent no diminution with nitrous gas, and a taper plunged into it was instantly extinguished. We may consequently conclude that it was nitrogene.

Now 2 cubic inches of nitrous gas weigh,686 grains, and 1,1 of nitrogene—,05, the quantity previously contained in the gas = to 1,05, 3,19. Hence,686 of nitrous gas would be composed of,367 oxygene, and ,319 nitrogene; and 100 grains would contain 53,4 oxygene, and 46,6 nitrogene.

IV. _Additional observations on the combustion of bodies in Nitrous Gas, and on its Composition._

Though phosphorus may be fused, and even sublimed, in nitrous gas, without producing the slightest luminous appearance,[103] yet when it is introduced into it in a state of active inflammation, it burns with almost as much vividness as in oxygene.[104] Hence it is evident, that at the heat of ignition, phosphorus is capable of attracting the oxygene from the nitrogene of nitrous gas.

[103] No luminous appearance is produced when phosphorus is introduced into _pure_ nitrous gas. It has been often observed, that phosphorus is luminous in nitrous gas, that has not been long in contact with water after its production. This phænomenon, I suspect, depends either on the decomposition of the nitric acid held in solution by the nitrous gas; or on the combination of the phosphorus with oxygene loosely adhering to the binary aëriform compound of nitric acid and nitrous gas. I have not yet examined if nitrous gas can be converted into nitrous oxide by long exposure to heated phosphorus: it appears, however, very probable.

[104] Perhaps this fact has been noticed before; I have not, however, met with it in any chemical work.

I attempted to analise nitrous gas, by introducing into a known quantity of it, confined by mercury, phosphorus, in a vessel containing a minute quantity of oxygene.[105] The phosphorus was inflamed with an ignited iron wire, by which, at the moment of the combustion, the vessel containing it was raised from the mercury into the nitrous gas. But after making in this way, five of six unsuccessful experiments, I desisted. When the communication between the vessels was made before the oxygene was nearly combined with the phosphorus, nitrous acid was formed, which instantly destroyed the combustion; when, on the contrary, the phosphorus was suffered to consume almost the whole of the oxygene, it was not sufficiently ignited when introduced, to decompose the nitrous gas.

[105] This mode of inflaming bodies in gases, not capable of supporting combustion at low temperatures, will be particularly described hereafter.

In one experiment, indeed, the phosphorus burnt for a moment in the nitrous gas; the diminution however was slight, and not more than ¼ of it was decomposed.

Sulphur, introduced in a state of vivid inflammation, into nitrous gas, was instantly extinguished.

I passed a strong electric shock through equal parts of hydrogene and nitrous gas, confined by mercury in a detonating tube; but no inflammation, or perceptible diminution, was produced.

19,2 grain measures of hydrogene were fired by the electric shock, with 10 of nitrous oxide, and 6 of nitrous gas; the diminution was to 17; and pale green sulphate of iron admitted to the residuum, was not discolored. Consequently the nitrous gas was decomposed by the hydrogene, and as will be hereafter more clearly understood, nearly as much nitrogene furnished by it, as would have been produced from half the quantity of nitrous oxide.

Suspecting that phosphorated hydrogene might inflame with nitrous gas, I passed the electric spark through 1 measure of phosphorated hydrogene, and 4 of nitrous gas; but no diminution was perceptible. I likewise passed the electric spark through 1 of nitrous gas, with 2 of phosphorated hydrogene, without inflammation.

Perhaps if I had tried many other different proportions of the gases, I should have at last discovered one, in which they would have inflamed; for, as will be seen hereafter, nitrous oxide cannot be decomposed by the compound combustible gases, except definite quantities are employed.

From Dr. Priestley’s experiments on iron and pyrophorus, and from the experiments I have detailed, on charcoal, phosphorus, and hydrogene, it appears that at certain temperatures, nitrous gas is decomposable by most of the combustible bodies: even the extinction of sulphur, when introduced into it in a state of inflammation, depends perhaps, on the smaller quantity of heat produced by the combustion of this body, than that of most others.

The analysis of nitrous gas by charcoal, as affording data for determining immediately the quantities of oxygene and nitrogene, ought to be considered as most accurate; and correcting it by mean calculations derived from the decomposition of nitrous gas by pyrophorus and hydrogene, and its conversion into nitrous oxide, a process to be described hereafter, we may conclude, that 100 grains of nitrous gas are composed of 55,95 oxygene, and 44,05 nitrogene; or taking away decimals, of 56 oxygene, and 44 nitrogene.

This estimation will agree very well with the mean proportions that would be given from Dr. Priestley’s experiments on the decomposition of nitrous gas by iron; but as he never ascertained the purity of his nitrous gas,[106] and probably employed different kinds in different experiments, it is impossible to fix on any one, from which accurate conclusions can be drawn.

Lavoisier’s estimation of the quantities of oxygene and nitrogene entering into the composition of nitrous gas, has been generally adopted. He supposes 64 parts of nitrous gas to be composed of 43½ of oxygene, and 20½ of nitrogene.[107]

[106] Elements English Trans. edit. i. pag. 216.

[107] Experiments and Observations, Vol. II. pag. 40, 2d. Ed.

The difference between this account and mine is very great indeed; but I have already, in Division 1st, pointed out sources of error in the experiments of this great man, on the decomposition of nitre by charcoal; which experiments were fundamental, both to his accounts of the constitution of nitrous acid, and nitrous gas.

V. _Of the absorption of Nitrous Gas by Water._

Amongst the properties of nitrous gas noticed by its great discoverer, is that of absorbability by water.

In exposing nitrous air to distilled water, Dr. Priestley found a diminution of the volume of gas, nearly equal to one tenth of the bulk of the water; and by boiling the water thus impregnated, he procured again a certain portion of the nitrous gas.

Humbolt, in his paper on eudiometry, mentions the diminution of nitrous gas by water. This diminution, he supposes to arise from the decomposition of a portion of the nitrous gas, by the water, and the consequent formation of nitrate of ammoniac.[108]

[108] He says, “On a observé, (depuis qu’on travaille sur le pureté de l’air) que le gaz nitreux, secoué avec l’eau, en souffre une diminution de volume. Quelques physiciens attribuent ce changement à une vraie absorption, à une dissolution du gaz nitreux dans l’eau; d’autres à l’air contenu dans les interstices de tous les fluides. Le cit. Vanbreda, à Delft, a fait des recherches très-exactes sur l’influence des eaux de pluie et de puit, sur les nombres eudiométriques; et les belles expériences du cit. Hassenfratz, sur l’abondance d’oxygène, contenue dans les eaux de neige et de pluie, sont supposer que l’air des interstices de l’eau joue un rôle important dans l’absorption du gaz nitreux. En comparant ces effets avec les phénomènes observé dans la decomposition du sulfate de fer, nous supposâmes, le cit. Tassaert et moi, que le simple contact du gaz nitreux avec l’eau distillée pourroit bien causer une décomposition de ce dernier. Nous examinâmes soigneusement une petite quantité d’eau distillée, secouée avec beaucoup de gas nitreux trés-pur, et nous trouvâmes, au moyen de la terre calcaire, et l’acide muriatique, qu’il s’y forme du _nitrate d’ammoniaque_. L’eau se décompose en cette opération, par un double affinité de l’oxygene pour le gaz nitreux, et de l’hydrogène pour l’azote; il se forme de l’acide nitrique et de l’_ammoniaque_; et, quoique la quantité du dernier paroisse trop petite pour en évaluer exactment la quantité, son existence cependant se manifeste, (à ne pas sans douter) par le dégagement des vapeurs, qui blanchissent dans la proximité de l’acide muriatique. Voilá un fait bien frappant que la composition d’une substance alcaline par le contact d’une acide, et de l’eau.”

Annales de Chimie, t. xxviii. pag. 153.

I confess, that even before the following experiments were made, I was but little inclined to adopt this opinion: the small diminution of nitrous gas by water, and the uniform limits of this diminution, rendered it extremely improbable.

_a._ To ascertain the quantity of nitrous gas absorbable by pure water, and the limits of absorption, I introduced into a glass retort about 5 ounces of water, which had been previously boiled for some hours. The neck of the retort was inverted in mercury, and the water made to boil. After a third of it had been distilled, so that no air could possibly remain in the retort, the remainder was driven over, and condensed in an inverted jar filled with mercury. To three cubic inches of this water,[109] confined in a cylinder graduated to,05 cubic inches, 5 cubic inches of nitrous gas, containing nearly one thirtieth nitrogene, were introduced.

[109] Which was certainly as free from air as it ever can be obtained.

After agitation for near an hour, rather more than ⁴/₂₀ of a cubic inch appeared to be absorbed; but though the process was continued for near two hours longer, no further diminution took place.

The remaining gas was introduced into a tube graduated to,02 cubic inches. It measured ¹⁴/₅₀; hence ¹¹/₅₀ had been absorbed.

Consequently, 100 cubic inches of pure water are capable of absorbing 11,8 of nitrous gas. In the water thus impregnated with nitrous gas I could distinguish no peculiar taste;[110] it did not at all alter the color of blue cabbage juice.

[110] Dr. Priestley found distilled water, saturated with nitrous air, to acquire an astringent taste and pungent smell. In some unboiled impregnated pump water, I once thought that I perceived a subacid taste; but it was extremely slight, and probably owing to nitrous acid formed by the union of the oxygene of the common air in the water, with some of the nitrous gas.

_b._ To determine if the absorption of nitrous gas was owing, to a decomposition of it by the water, as Humbolt has supposed, or to a simple solution; I procured some nitrous gas from nitrous acid and mercury, containing about one seventieth nitrogene. ,5 cubic inches of it, mingled with ,25, of oxygene, from sulphuric acid and manganese left a residuum of,03. 5 cubic inches more were introduced to 3 of water, procured in the same manner as in the last experiment, in the same cylinder. After the diminution was complete, the cylinder was transferred in a small vessel containing mercury, into a water bath, and nearly covered by the water.

As the bath was heated, small globules of gas were given out from the impregnated water, and when it began to boil, the production of gas was still more rapid. After an hour’s ebullition, the volume of heated gas was equal to 1,4 cubic inches nearly.

The cylinder was now taken out of the bath, and quickly rendered cool by being placed in a water apparatus. At the common temperature the gas occupied, as nearly as possible, the space of,5 cubic inches: these,5 mingled with,25 of oxygene, of the same kind as that employed before, left a residuum nearly equal to,03.

From this experiment, which was repeated with nearly the same results, it is evident,

1. That nitrous gas is not decomposable by pure water.

2. That the diminution of volume of nitrous gas placed
in contact with water, is owing to a simple solution
of it in that fluid.

3. That at the temperature of 212°, nitrous gas is
incapable of remaining in combination with water.

Humbolt’s opinion relating to the decomposition of nitrous gas by water, is founded upon the disengagement of vapor from distilled water impregnated with nitrous gas, by means of lime, which became white in the proximity of the muriatic acid. But this is a very imperfect, and fallacious test, of the presence of ammoniac. I have this day, April 2, 1800, heated 4 cubic inches of distilled water, impregnated with nitrous gas, with caustic lime; the vapor certainly became a little whiter when held over a vessel containing muriatic acid; but the vapor of distilled water produced precisely the same appearance,[111] which was owing, most likely, to the combination of the acid with the aqueous vapor. Indeed, when I added a particle of nitrate of ammoniac, which might have equalled one twentieth of a grain, to the lime and impregnated water, the increased whiteness of the vapor was but barely perceptible, though this quantity of nitrate of ammoniac is much more considerable than that which could have been formed, even supposing the nitrous gas decomposed.

[111] As carbonic acid and ammoniac are both products of animalisation, is it not probable that our common waters particularly those in, and near towns and cities, contain carbonate of ammoniac? If so, this salt will always exist in them after distillation. In the experiments on carbonate of ammoniac, to which I have often alluded, I found, in distilling a solution of this salt in water, that before half of the water had passed into the recipient, the carbonate of ammoniac had sublimed; so that the distilled solution was much stronger than before, whilst the water remaining in the retort was tasteless. Will this supposition at all explain Humbolt’s mistake?

VI. _Of the absorption of Nitrous Gas by Water of different kinds._

In agitating nitrous gas over spring water, the diminution rarely amounts to more than one thirtieth, the volume of water being taken as unity. I at first suspected that this great differcnce in the quantity of gas absorbed by spring water, and pure water, depended on carbonic acid contained in the last, diminishing the attraction of it for nitrous gas: but by long boiling a quantity of spring water confined by mercury, I obtained from it about one twentieth of its bulk of air, which gave nearly the same diminution with nitrous gas, as atmospheric air.

This fact induced me to refer the difference of diminution to the decomposition of the atmospheric air held in solution by the water, the oxygene of which I supposed to be converted into nitric acid, by the nitrous gas, whilst the nitrogene was liberated; and hence the increased residuum.

_a._ I exposed to pure water, that is, water procured by distillation under mercury, nitrous gas, containing a known quantity of nitrogene. After the absorption was complete, I found the same quantity of nitrogene in the residuum, as was contained in a volume of gas equal to the whole quantity employed.

_b._ Spring water boiled for some hours, and suffered to cool under mercury, absorbed a quantity of nitrous gas equal to one thirteenth of its bulk; which is not much less than that absorbed by pure water.

_c._ I exposed to spring water, 10 measures of nitrous gas; the composition of which had been accurately ascertained; the diminution was one twenty-eighth, the volume of water being taken as unity. On placing the residuum in contact with solution of sulphate of iron, the nitrogene remaining was nearly one twentieth more than had been contained by the gas before its exposure to water.

_d._ Distilled water was saturated with common air, by being agitated for some time in the atmosphere. Nitrous gas placed in contact with this water, underwent a diminution of ¹/₁₈; the volume of water being unity. The gas remaining after the absorption contained about one twenty-seventh nitrogene more than before.

_e._ Nitrous gas exposed to water combined with about one fourth of its volume of carbonic acid, diminished to ¹/₃₂[112] nearly. The remainder contained little or no superabundant nitrogene.

[112] The water still being unity.

From these observations it appears, that the different degrees of diminution of nitrous gas by different kinds of water, may depend upon various causes.

1. Less nitrous gas will be absorbed by water holding in solution earthy salts, than by pure water; and in this case the diminution of the attraction of water for nitrous gas will probably be in the ratio of the quantities of salt combined with it. _a._ _b._

2. The apparent diminution of nitrous gas in water, holding in solution atmospheric air, will be less than in pure water, though the absolute diminution will be greater; for the same portion will be absorbed, whilst another portion is combined with the oxygene of the atmospheric air contained in the water; and from the disengagement of the nitrogene of this air, arises an increased residuum. _c._ _d._

3. Probably in waters containing nitrogene, hydrogene, and other gases, absorbable only to a slight extent, the apparent diminution will be less, on account of the disengagement of those gases from the water, by the stronger affinity of nitrous gas for that fluid.

4. In water containing carbonic acid, and probably some other acid gases, the diminution will be small in proportion to the quantity of gas contained in the water: the affinity of this fluid for nitrous gas being diminished by its greater affinity for the substance combined with it. _e._

The different diminution of nitrous gas when agitated in different kinds of water, has been long observed by experimenters on the constituent parts of the atmosphere, and various solutions have been given of the phænomenon; the most singular is that of Humbolt.[113] He supposes that the apparent diminution of nitrous gas is less in spring water than distilled water, on account of the decomposition of the carbonate of lime contained in the spring water, by the nitrous acid formed from the contact of nitrous gas with the water; the carbonic acid disengaged from this decomposition increasing the residuum.

[113] He says “100 parties de gaz nitreux, (à 0.14 d’azote) secouées avec l’eau distillée, récemment cuite, diminuent en volume de 0.11, ou 0.12. Ce même gaz, en contact avec l’eau de puits, ne perd que 0.02. La cause de cette différence de 0.9, ou 0.10, ne doit pas être attribuée ni à l’impurité de l’air atmosphérique, contenu dans les interstices de l’eau, ni à la décomposition de cette eau même. Elle n’est qu’apparente; car l’acide nitrique, qui se forme par le contact du gaz nitreux avec l’eau de puits, en décompose le carbonate de chaux. Il se dégage de l’acide carbonique, qui, en augmentant le volume du residu, rend l’absorption du gaz nitreux moins sensible. Pour déterminer la quantité de cet acide carbonique, je lavai le résidu avec de l’eau de chaux. Dans un grand nombre d’expériences, le volume diminua de 0.09, ou 0.07. Il faut en conduire que l’eau de puits absorbe réellement 9 + 2, ou 7 + 2 parties de gas nitreux, c’est-à-dire, à peu-près la même quantité que l’eau distillée.”

Annales De Chimie, xxviii. pag. 154.

This opinion may be confuted without even reference to my observations. It is, indeed, altogether unworthy of a philosopher, generally acute and ingenious. He seems to have forgotten that carbonic acid is absorbable by water.

VII. _Of the absorption of Nitrous Gas, by solution of pale green Sulphate of Iron._