Chapter I: Part 1

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RESEARCHES,
CHEMICAL AND PHILOSOPHICAL;
CHIEFLY CONCERNING
NITROUS OXIDE,

OR
DEPHLOGISTICATED NITROUS AIR,
AND ITS
RESPIRATION.

By HUMPHRY DAVY,

SUPERINTENDENT OF THE MEDICAL PNEUMATIC
INSTITUTION.

LONDON:

PRINTED FOR J. JOHNSON, ST. PAUL’S CHURCH-YARD,
BY BIGGS AND COTTLE, BRISTOL,
1800.

CONTENTS.

INTRODUCTION, xi.

RESEARCH I.
_Into the analysis of_ NITRIC ACID _and_ NITROUS GAS,
_and the production of_ NITROUS OXIDE.

DIVISION I.
EXPERIMENTS _and_ OBSERVATIONS _on the composition
of_ NITRIC ACID, _and on its combinations with_
WATER _and_ NITROUS GAS.

1. Preliminaries 1
2. Production of aëriform Nitrous Acid 3
3. Specific gravity of Gases 6
4. Experiment on the formation of Nitrous Acid 11
5. Conclusions 17
6. Experiments on the combination of Nitrous Gas
with Nitric Acid 17
7. Additional Experiments 23
8. Conclusions 29
9. Mr. THOMSON’S Theory of the difference
between Nitric and Nitrous Acid 30
10. Composition of the different Nitrous Acids 36
11. Combination of Nitric Acid with Water 38
12. Of Nitrous Vapor 42
13. Comparison of the results with those of
Cavendish and Lavoisier 43

DIVISION II.
EXPERIMENTS _and_ OBSERVATIONS _on the composition
of_ AMMONIAC _and on its combinations with_ WATER
_and_ NITRIC ACID.

1. Analysis of Ammoniac 56
2. Specific gravity of Ammoniac 62
3. Of the quantities of true Ammoniac in
Ammoniacal Solutions 65
4. Composition of Nitrate of Ammoniac 71
5. Decomposition of Carbonate of Ammoniac,
by Nitrous Acid 75
6. Decomposition of Sulphate of Ammoniac by Nitre 77
7. Non-existence of Ammoniacal Nitrites 79
8. Sources of error in Analysis 80
9. Loss in Solutions of Nitrate of Ammoniac
during evaporation 83

DIVISION III.
DECOMPOSITION _of_ NITRATE _of_ AMMONIAC—_Preparation
of_ RESPIRABLE NITROUS OXIDE.

1. Of the heat required for the decomposition of
Nitrate of Ammoniac 84
2. Decomposition of Nitrate of Ammoniac—Production
of respirable Nitrous Oxide—its properties 86
3. Of the Gas remaining after the absorption of
Nitrous Oxide by Water 89
4. Specific Gravity of Nitrous Oxide 94
5. Analysis of Nitrous Oxide 95
6. Minute examination of the decomposition
of Nitrate of Ammoniac 101
7. Of the heat produced during the decomposition
of Nitrate of Ammoniac 108
8. Decomposition of Nitrate of Ammoniac at
high temperatures 109
9. Speculations on the decompositions of Nitrate
of Ammoniac 113
10. Of the preparation of Nitrous Oxide for
experiments on respiration 117

DIVISION IV.
EXPERIMENTS _and_ OBSERVATIONS _on the composition of_
NITROUS GAS, _and on its absorption by different
bodies_.

1. Preliminaries 122
2. Analysis of Nitrous Gas by Charcoal 126
3. Analysis of Nitrous Gas by Pyrophorus 132
4. Additional observations on the composition of
Nitrous Gas 134
5. Absorption of Nitrous Gas by Water 140
6. Absorption of Nitrous Gas by Water of
different kinds 147
7. Absorption of Nitrous Gas by solution of
pale green Sulphate of Iron 152
8. Absorption of Nitrous Gas by solution of
green muriate of Iron 179
9. By Solution of Nitrate of Iron 187
10. By other metallic Solutions 189
11. Action of sulphurated Hydrogene on solution
of green sulphate of iron impregnated with
Nitrous Gas 191
12. Additional Observations 193

DIVISION V.
EXPERIMENTS _and_ OBSERVATIONS _on the production of_
NITROUS OXIDE _from_ NITROUS GAS _and_ NITRIC ACID
_in different modes_.

1. Preliminaries 197
2. Conversion of Nitrous Gas into Nitrous Oxide
by alkaline sulphites 199
3. By Muriate of Tin 202
4. By Sulphurated Hydrogene 203
5. Decomposition of Nitrous Gas by Nascent
Hydrogene 206
6. Miscellaneous Observations 209
7. Recapitulation 211
8. Production of Nitrous Oxide from Metallic
Solutions 213
9. Additional Observations relating to the
production of Nitrous Oxide 219
10. Decomposition of Aqua regia by platina,
and evolution of a gas analogous to oxygenated
muriatic acid, and nitrogene 222
11. Action of the electric spark on a mixture
of Nitrogene and Nitrous gas 229
12. General remarks on the production
of Nitrous Oxide 231

RESEARCH II.
_Into the combinations of_ NITROUS OXIDE,
_and its decomposition_.

DIVISION I.
EXPERIMENTS _and_ OBSERVATIONS _on the combinations
of_ NITROUS OXIDE.

1. Combination of Water with Nitrous Oxide 235
2. —— of Nitrous Oxide with fluid inflammable
bodies 240
3. Action of fluid Acids on Nitrous Oxide 244
4. —— of Saline Solutions 245
5. —— of Gases 248
6. Action of aëriform Nitrous Oxide on the
alkalies—History of the discovery of the
combinations of Nitrous Oxide, with the
alkalies 254
7. Combination of Nitrous Oxide with Potash 262
8. Combination of Nitrous Oxide with Soda 268
9. —— —— —— with Ammoniac 269
10. Probability of forming compounds of
Nitrous Oxide and the alkaline earths 273
11. Additional Observations 274
12. The properties of Nitrous oxide resemble
those of Acids 276

DIVISION II.
_Decomposition of_ NITROUS OXIDE _by combustible Bodies_.

1. Preliminaries 278
2. Conversion of Nitrous Oxide into Nitrous Acid
and a gas analogous to Atmospheric Air
by ignition 279
3. Decomposition of Nitrous Oxide by Hydrogene 286
4. —— —— —— by Phosphorus 293
5. —— —— by Phosphorated Hydrogene 300
6. —— —— by Sulphur 303
7. —— —— by Sulphurated Hydrogene 306
8. —— —— by Charcoal 311
9. —— —— by Hydrocarbonate 313
10. Combustion of Iron in Nitrous Oxide 316
11. —— of Pyrophorus 318
12. —— of the Taper 319
13. —— of different Compound Bodies 321
14. General Conclusions relating to the
decomposition of Nitrous Oxide, and
to its analysis 322
15. Observations on the combinations of Oxygene
and Nitrogene 325

RESEARCH III.
_Relating to the_ RESPIRATION _of_ NITROUS OXIDE
_and_ OTHER GASES.

DIVISION I.
EXPERIMENTS _and_ OBSERVATIONS _on the effects produced
upon Animals by the respiration of_ NITROUS OXIDE.

1. Preliminaries 333
2. On the respiration of Nitrous Oxide by
warm-blooded Animals 336
3. Effects of the respiration of Nitrous Oxide
upon Animals, as compared with those produced
by their immersion in Hydrogene and Water 343
4. Of the changes effected in the organisation of
warm-blooded Animals, by the respiration of
Nitrous Oxide 347
5. Of the respiration of mixtures of Nitrous Oxide
and other Gases, by warm-blooded Animals 358
6. Recapitulation of facts relating to the
respiration of Nitrous Oxide, by warm-blooded
Animals 360
7. Of the respiration of Nitrous Oxide,
by amphibious Animals 362
8. Effects of Solution of Nitrous Oxide on Fishes 366
9. Effects of Nitrous Oxide on Insects 370

DIVISION II.
_Of the changes effected in_ NITROUS OXIDE
_and other Gases, by the Respiration of Animals_.

1. Preliminaries 373
2. Absorption of Nitrous Oxide by Venous Blood 374
3. Of the changes effected in Nitrous Oxide
by Respiration 388
4. Respiration of Hydrogene 400
5. Additional Observations and Experiments on the
Respiration of Nitrous Oxide 411
6. Of the Respiration of Atmospheric Air 429
7. Respiration of Oxygene 439
8. Observations on the changes effected in the
blood by Atmospheric Air and Oxygene 445
9. Observations on the Respiration of Nitrous Oxide 449

RESEARCH IV.
_Relating to the_ EFFECTS _produced by the_
RESPIRATION _of_ NITROUS OXIDE
_upon different_ INDIVIDUALS.

DIVISION I.
HISTORY _of the Discovery_.—EFFECTS _produced
by the Respiration of different_ GASES.

1. Respirability of Nitrous Oxide 456
2. Effects of Nitrous Oxide 458
3. General Effects of Nitrous Oxide on the Health 464
4. Respiration of Hydrogene 466
5. —— of Nitrogene 467
6. Effects of Hydrocarbonate 468
7. —— of Carbonic Acid 472
8. —— of Oxygene 473
9. —— of Nitrous Gas 475
10. Most extensive action of Nitrous Oxide
produces no debility 485

DIVISION II.
DETAILS _of the Effects produced by the Respiration
of_ NITROUS OXIDE _upon different Individuals,
furnished by Themselves_.

1. Detail of Mr. J. W. Tobin 497
2. —— of Mr. W. Clayfield 502
3. Letter from Dr. Kinglake 503
4. Detail of Mr. Southey 507
5. Letter from Dr. Roget 509
6. Letter from Mr. James Thomson 512
7. Detail of Mr. Coleridge 516
8. —— of Mr. Wedgwood 518
9. —— of Mr. G. Burnet 520
10. —— of Mr. T. Pople 521
11. —— of Mr. Hammick 522
12. —— of Dr. Blake 524
13. —— of Mr. Wanfey 525
14. —— of Mr. Rickman 526
15. —— of Mr. Lovell Edgworth 527
16. —— of Mr. G. Bedford 528
17. —— of Miss Ryland 530
18. Letter from Mr. M. M. Coates 530

DIVISION III.
_Abstracts from additional Details—Observations on
the effects of_ NITROUS OXIDE,
_by_ Dr. BEDDOES—_Conclusion_.

1. Abstracts from additional details 533
2. Of the effects of Nitrous Oxide on
delicate females 537
3. Observations on the effects of Nitrous Oxide
by Dr. BEDDOES 541
4. Conclusion 548

APPENDIX.
No. I. Of the effects of Nitrous Oxide
on Vegetables 561
No. II. Table of the Weight and Composition
of the combinations of Nitrogene 566
No. III. Additional Observations 567
No. IV. Description of a Mercurial Airholder,
and Breathing Machine,
by Mr. W. CLAYFIELD. 573
No. V. Proposals for the Preservation of
Accidental Observations in Medicine.
By Dr. BEDDOES. 577

INTRODUCTION.

In consequence of the discovery of the respirability and extraordinary effects of nitrous oxide, or the dephlogisticated nitrous gas of Dr. Priestley, made in April 1799, in a manner to be particularly described hereafter,[1] I was induced to carry on the following investigation concerning its composition, properties, combinations, and mode of operation on living beings.

[1] A short account of this discovery has been given in Dr. Beddoes’s Notice of some Observations made at the Pneumatic Institution, and in Mr. Nicholson’s Phil. Journal for May and December 1799.

In the course of this investigation, I have met with many difficulties; some arising from the novel and obscure nature of the subject, and others from a want of coincidence in the observations of different experimentalists on the properties and mode of production of the gas. By extending my researches to the different substances connected with nitrous oxide; nitrous acid, nitrous gas and ammoniac; and by multiplying the comparisons of facts, I have succeeded in removing the greater number of those difficulties, and have been enabled to give a tolerably clear history of the combinations of oxygene and nitrogene.

By employing both analysis and synthesis whenever these methods were equally applicable, and comparing experiments made under different circumstances, I have endeavoured to guard against sources of error; but I cannot flatter myself that I have altogether avoided them. The physical sciences are almost wholly dependant on the minute observation and comparison of properties of things not immediately obvious to the senses; and from the difficulty of discovering every possible mode of examination, and from the modification of perceptions by the state of feeling, it appears nearly impossible that all the relations of a series of phænomena can be discovered by a single investigation, particularly when these relations are complicated, and many of the agents unknown. Fortunately for the active and progressive nature of the human mind, even experimental research is only a method of approximation to truth.

In the arrangement of facts, I have been guided as much as possible by obvious and simple analogies only. Hence I have seldom entered into theoretical discussions, particularly concerning light, heat, and other agents, which are known only by isolated effects.

Early experience has taught me the folly of hasty generalisation. We are ignorant of the laws of corpuscular motion; and an immense mass of minute observations concerning the more complicated chemical changes must be collected, probably before we shall be able to ascertain even whether we are capable of discovering them. Chemistry in its present state, is simply a partial history of phænomena, consisting of many series more or less extensive of accurately connected facts.

With the most important of these series, the arrangement of the combinations of oxygene or the antiphlogistic theory discovered by Lavoisier, the chemical details in this work are capable of being connected.

In the present state of science, it will be unnecessary to enter into discussions concerning the importance of investigations relating to the properties of physiological agents, and the changes effected in them during their operation. By means of such investigations, we arrive nearer towards that point from which we shall be able to view what is within the reach of discovery, and what must for ever remain unknown to us, in the phænomena of organic life. They are of immediate utility, by enabling us to extend our analogies so as to investigate the properties of untried substances, with greater accuracy and probability of success.

The first Research in this work chiefly relates to the production of nitrous oxide and the analysis of nitrous gas and nitrous acid. In this there is little that can be properly called mine; and if by repeating the experiments of other chemists, I have sometimes been able to make more minute observations concerning phænomena, and to draw different conclusions, it is wholly owing to the use I have made of the instruments of investigation discovered by the illustrious fathers of chemical philosophy,[2] and so successfully applied by them to the discovery of truth.

[2] Cavendish, Priestley, Black, Lavoisier, Scheele, Kirwan, Guyton, Berthollet, &c.

In the second Research the combinations and composition of nitrous oxide are investigated, and an account given of its decomposition by most of the combustible bodies.

The third Research contains observations on the action of nitrous oxide upon animals, and an investigation of the changes effected in it by respiration.

In the fourth Research the history of the respirability and extraordinary effects of nitrous oxide is given, with details of experiments on its powers made by different individuals.

I cannot close this introduction, without acknowledging my obligations to Dr. Beddoes. In the conception of many of the following experiments, I have been aided by his conversation and advice. They were executed in an Institution which owes its existence to his benevolent and philosophic exertions.

_Dowry-Square, Hotwells, Bristol._
_June 25th, 1800._

RESEARCH I.

CONCERNING THE ANALYSIS OF
NITRIC ACID AND NITROUS GAS
AND THE PRODUCTION OF
NITROUS OXIDE.

_Lowry sculpᵗ._]

RESEARCH I.

INTO THE PRODUCTION AND ANALYSIS OF NITROUS OXIDE, AND THE AËRIFORM FLUIDS RELATED TO IT.

DIVISION I.

_EXPERIMENTS and OBSERVATIONS on the composition
of_ NITRIC ACID, _and on its combinations
with_ WATER _and_ NITROUS GAS.

I. Though since the commencement of Pneumatic Chemistry, no substance has been more the subject of experiment than Nitrous Acid; yet still the greatest uncertainty exists with regard to the quantities of the principles entering into its composition.

In comparing the experiments of the illustrious Cavendish on the synthesis of nitrous acid, with those of Lavoisier on the decomposition of nitre by charcoal, we find a much greater difference in the results than can be accounted for by supposing the acid formed, and that decomposed, of different degrees of oxygenation.

In the most accurate experiment of Cavendish, when the nitrous acid appeared to be in a state of deoxygenation, 1 of nitrogene combined with about 2,346 of oxygene.[3] In an earlier experiment, when the acid was probably fully oxygenated, the nitrogene employed was to the oxygene nearly as 1 to 2,92.[4]

Lavoisier, from his experiments on the decomposition of nitre, and combination of nitrous gas and oxygene, concludes, that the perfectly oxygenated, or what he calls nitric acid, is composed of nearly 1 nitrogene, with 3,9 of oxygene; and the acid in the last state of deoxygenation, or nitrous acid, of about 3 oxygene with 1 nitrogene.[5]

[3] Phil. Trans. v. 78, p. 270.

[4] Phil. Trans. v. 75 p. 381.

[5] Elem. Kerr’s Trans. page 76, and 216, and Mem. des Sav. Etrang. tom. 7, page 629.

Great as the difference is between the estimations of these philosophers, we find differences still greater in the accounts of the quantities of nitrous gas necessary to saturate a given quantity of oxygene, as laid down by very accurate experimentalists. On the one hand, Priestley found 1 of oxygene condensed by 2 of nitrous gas, and Lavoisier by 1⅞. On the other, Ingenhouz, Scherer, and De la Metherie, state the quantity necessary to be from 3 to 5.[6] Humbolt, who has lately investigated Eudiometry with great ingenuity, considers the mean quantity of nitrous gas necessary to saturate 1 of oxygene, as about 2,55.[7]

[6] Ingenhouz sur les Vegetaux, pag. 205. De la Metherie. Essai sur differens Airs, pag. 252.

[7] Annales de Chimie, tome 28, p. 168.

II. To reconcile these different results is impossible, and the immediate connection of the subject with the production of nitrous oxide, as well as its general importance, obliged me to search for means of accurately determining the composition of nitrous acid in its different degrees of oxygenation.

The first desideratum was to ascertain the nature and composition of a fluid acid, which by being deprived of, or combined with nitrous gas, might become a standard of comparison for all other acids.

To obtain this acid I should have preferred the immediate combination of oxygene and nitrogene over water by the electric spark, had it been possible to obtain in this way by a common apparatus sufficient for extensive examination; but on carefully perusing the laborious experiments of Cavendish, I gave up all thoughts of attempting it.

My first experiments were made on the decomposition of nitre, formed from a known quantity of pale nitrous acid of known specific gravity, by phosphorus, tin, and charcoal: but in those processes, unascertainable quantities of nitrous acid, with excess of nitrous gas, always escaped undecompounded, and from the non-coincidence of results, where different quantities of combustible substances were employed, I had reasons for believing that water was generally decomposed.

Before these experiments were attempted, I had analized nitrous gas and nitrous oxide, in a manner to be particularly described hereafter; so that a knowledge of the quantities of nitrous gas and oxygene entering into the composition of any acid, enabled me to determine the proportions of nitrogene and oxygene it contained. In consequence of which I attempted to combine together oxygene and nitrous gas, in such a manner as to absorb the nitrous acid formed by water, in an apparatus by which the quantities of the gases employed, and the increase of weight of the water, might be ascertained; but this process likewise failed. It was impossible to procure the gases perfectly free from nitrogene, and during their combination, this nitrogene made to pass into a pneumatic apparatus communicating with a vessel containing the water carried over with it, much nitrous acid vapor, of different composition from the acid absorbed.

After many unsuccessful trials, Dr. Priestley’s experiments on nitrous vapor[8] induced me to suppose that oxygene and nitrous gas, made to combine out of the contact of bodies having affinity for oxygene, would remain permanently aëriform, and on throwing them separately into an exhausted glass balloon, I found that this was actually the case; increase of temperature was produced, and orange colored nitrous acid gas formed, which after remaining for many days in the globe, at a temperature below 56°, did not in the slightest degree condense.

[8] Experiments and Observations, Vol. iii. last edition, page 105, &c.

This fact afforded me the means not only of forming a standard acid, but likewise of ascertaining the specific gravity of nitrous acid in its aëriform state.

III. Previous to the experiment, for the purpose of correcting incidental errors, I was induced to ascertain the specific gravity of the gases employed, particularly as I was unacquainted with any process by which the weight of nitrous gas had been accurately determined. Mr. Kirwan’s estimation, which is generally adopted, being founded upon the comparison of the loss of weight of a solution of copper in dilute nitrous acid, with the quantity of gas produced.[9]

The instruments that I made use of for containing and measuring my gases, were two mercurial airholders graduated to the cubic inch of Everard, and furnished with stop-cocks.[10]

[9] When copper is dissolved in dilute nitrous acid, certain quantities of nitrogene are generally produced, likewise the nitrous gas carries off in solution some nitrous acid.

[10] This airholder, considered as a pneumatic instrument, is of greater importance, and capable of a more extensive application than any other. It was invented by Mr. W. CLAYFIELD, and in its form is analogous to Mr. WATT’S hydraulic bellows, consisting of a glass bell playing under the pressure of the atmosphere, in a space between two cylinders filled with mercury. A particular account of it will be given in the appendix.

They were weighed in a glass globe, of the capacity of 108 cubic inches, which with the small glass stop-cock affixed to it, was equal, when filled with atmospheric air, to 1755 grains. The balance that I employed, when loaded with a pound, turned with less than one eighth of a grain.

Into a mercurial airholder, of the capacity of 200 cubic inches, 160 cubic inches of nitrous gas were thrown from a solution of mercury in nitrous acid.

70 measures of this were agitated for some minutes in a solution of sulphate of iron,[11] till the diminution was complete. The nitrogene remaining hardly filled a measure; and if we suppose with Humbolt[12] that a very small portion of it was absorbed with the nitrous gas, the whole quantity it contained may be estimated at 0,0142, or ¹/₇₀.

[11] This absorption will be hereafter particularly treated of.

[12] Annales de Chimie. Tome xviii. page 139.

75 cubic inches received from the airholder into an exhausted balloon, increased it in weight 25,5 grains; thermometer being 56°, and barometer 30,9. And allowing for the small quantity of nitrogene in the gas, 100 cubic inches of it will weigh 34.3 grains.

One hundred and thirty cubic inches of oxygene were procured from oxide of manganese and sulphuric acid, by heat, and received in another mercurial airholder.

10 measures of it, mingled with 26 of the nitrous gas, gave, after the residuum was exposed to solution of sulphate of iron, rather more than one measure. Hence we may conclude that it contained about 0,1 nitrogene.

60 cubic inches of it weighed 20,75 grains; and accounting for the nitrogene contained in these, 100 grains of pure oxygene will weigh 35,09 grains.

Atmospherical air was decomposed by nitrous gas in excess; and the residuum washed with solution of sulphate of iron till the Nitrogene remained pure; 87 cubic inches of it weighed 26,5 grains, thermometer being 48°, barometer 30,1; 100 will consequently weigh 30,45.

90 cubic inches of the air of the laboratory not deprived of its carbonic acid, weighed 28,75 grains; thermometer 53, barometer 30: 100 cubic inches will consequently weigh 31,9.[13] 16 measures of this air, with 16 nitrous gas, of known composition, diminished to 19. Hence it contained about,26 oxygene.[14]

In comparing my results with those of Lavoisier and Kirwan, the estimation of the weights of nitrogene and oxygene is very little different, the corrections for temperature and pressure being made, from that of those celebrated philosophers. The first makes oxygene to weigh[15] 34,21, and nitrogene 30,064 per cent; and the last, oxygene 34,[16] and nitrogene 30,5.

[13] A table of the specific gravities of these gases, and other gases, hereafter to be mentioned, reduced to a barometrical and thermometrical standard, will be given in the appendix.

[14] 40 measures, exposed to solution of potash, gave an absorption of not quite a quarter of a measure: hence it contained an inconsiderable quantity of carbonic acid.

[15] Traité Elementaire.

[16] Essai sur le phlogistique, page 30.

The specific gravity of nitrous gas, according to Kirwan, is to that of common air as 1194 to 1000. Hence it should weigh about 37 grains per cent. This difference from my estimation is not nearly so great as I expected to have found it.[17]

IV.[18] The thermometer in the laboratory standing at 55°, and the barometer at 30,1, I now proceeded to my experiment. The oxygene that I employed was of the same composition as that which I had previously weighed. The nitrous gas contained,0166 nitrogene.

For the purpose of combining the gases, a glass balloon was procured, of the capacity of 148 cubic inches, with a glass stop-cock adapted to it, having its upper orifice tubulated and graduated for the purpose of containing and measuring a fluid. The whole weight of this globe and its appendages, when filled with common air, was 2066,5 grains.

[17] The diminution of the specific gravity of the gas from the quantity of nitrogene evolved in his experiment, probably destroyed, in some measure, the source of error from the nitrous acid carried over.

[18] Experiment I.

It was partially exhausted by the air-pump, and lost in weight just 32 grains. From whence we may conclude that about 15 grains of air remained in it.

In this state of exhaustion it was immediately cemented to the stop-cock of the mercurial airholder, and the communication being made with great caution, 82 cubic inches of nitrous gas rushed into the globe, on the outside of which a slight increase of temperature was perceived, while the gases on the inside appeared of a deep orange.

Before the common temperature was restored, the communication was stopped, and the globe removed. The increase of weight was 29,25 grains; whence it appeared that 1,14 grains of common air, part of which had been contained in the stop-cocks, had entered with the nitrous gas.

Whilst it was cooling, from the accidental loosening of the stopper of the cock, 3 grains more of common air entered.[19]

[19] That no greater contraction took place depended on the solution of the nitrous acid formed in the nitrous gas; a phænomenon to be explained hereafter.

The communication was now made between the globe and the mercurial airholder containing oxygene. 64 cubic inches were slowly pressed in, when the outside of the globe became warmer, and the color on the inside changed to a very dark orange. As it cooled, 6 cubic inches more slowly entered; but no new increase of temperature, or change of color took place.

The globe being now completely cold, was stopped, removed, and weighed; it had gained 24,5 grains, from whence it appears that 0,4 grains of common air contained in the stop-cocks, had entered with the oxygene.[20]

[20] I judged it expedient always to ascertain the quantity of air in the stop-cocks by weight, as it was impossible to join them so as to have always an equal capacity. The upper tubes of the two stop-cocks not joined, contained nearly an inch and half.

To absorb the nitrous acid gas, 41 grains of water were introduced by the tube of the stop-cock, which though closed as rapidly as possible, must have suffered nearly,5 grains of air to enter at the same time, as the increase of weight was 41,5 grains. The dark orange of the globe diminished rapidly; it became warm at the bottom, and moist on the sides. After a few minutes the color had almost wholly disappeared.

To ascertain the quantity of aëriform fluid absorbed, the globe was again attached to the mercurial air apparatus, containing 140 cubic inches of common air. When the communication was made, 51 cubic inches rushed in, and it gained in weight 16,5 grains.

A quantity of fluid equal to 54 grains was now taken out of the globe. On examination it proved to be slightly tinged with green, and occupied a space equal to that filled by 41,5 grains of water. Its specific gravity was consequently 1,301.

To ascertain if any unabsorbed aëriform nitrous acid remained in the globe, 13 grains of solution of ammonia were introduced in the same manner as the water, and after some minutes, when the white vapor had condensed, the communication was again made with the mercurial airholder containing common air. A minute quantity entered, which could not be estimated at more than three fourths of an inch, and the globe was increased in weight about 13,25 grains.[21]

Common air was now thrown into the globe till the residual gases of the experiment were judged to be displaced; it weighed 2106,5 grains, that is, 40 grains more than it had weighed when filled with common air before the experiment.[22]

[21] That is, by the solution of ammonia, and air.

[22] The following is an account of the increase and diminution of weight of the globe, as it was noted in the journal.

Globe filled with common air gr. 2066,5
After exhaustion 2034,5
After introduction of nitrous gas, 82 cubic inches 2064,25
After the accidental admission of common air 2067,25
After the admission of oxygene 2091,75
—— —— 41 grains of water 2133,25
—— —— 51 cubic inches of air 2149,75
Taken out 54 grains of solution 2095,75
Introduced 13 grains of ammoniacal solution 2109,25
After introduction of common air 2106,5

And if from those 40 grains we take 13 for the solution of ammonia introduced, the remainder, 27, will be the quantity of solution of nitrous acid in water remaining in the globe, which added to 54, equals 81 grains, the whole quantity formed; but if from this be taken 41 grains, the quantity of water, the remainder 40 grains, will be the quantity of nitrous acid gas absorbed in the solution.

To find the absolute quantity of nitrous acid formed, we must find the specific gravity of that absorbed; but as during, and after its absorption, 17 grains of air, equal to 53,2 cubic inches entered, it evidently filled such a space. 53,2 cubic inches of it consequently weigh 40 grains, and 100 cubic inches 75,17 grains. Then,75 cubic inches weigh,56 grains, and this added to 40, makes 40,56 grains, equal to 53,95 cubic inches, the whole quantity of aëriform nitrous acid produced.

But the quantity of nitrous gas entering into this, allowing for the nitrogene it contained, is 27,6 grains, equal to about 80,5 cubic inches; and the oxygene is 40,56-27,6 = to 12,96 grains, or 36,9 cubic inches.

V. There could exist in this experiment no circumstance connected with inaccuracy, except the impossibility of very minutely determining the quantities of common air which entered with the gases from the stop-cocks. But if errors have arisen from this source, they must be very inconsiderable; as will appear from a calculation of the specific gravity of the nitrous acid gas, founded on the volume of the gases that entered the globe.

The air that remained in the globe
after exhaustion was 15 grains = 47[23] cub. in.
The nitrous gas introduced was 82
Common air 13
Oxygene 70
Common air 1
——
Whole quantity of air thrown into the globe 213
From which subtract its capacity 148
——
The remainder is 65

[23] Decimals are omitted, because the excess of the two first numbers is exactly corrected by the deficiency of the last.

And this remainder taken from 80,5 nitrous gas + 36,9 oxygene, leaves 52,4 cubic inches, which is the space occupied by the nitrous acid gas, and which differs from 53,95 only by 1,55 cubic inches.

I ought to have observed, that before this conclusive experiment, two similar ones had been made. In comparing the results of one of them, performed with the assistance of my friend, Mr. JOSEPH PRIESTLEY, Dr. PRIESTLEY’S eldest son, and chiefly detailed by him in the journal, I find a coincidence greater than could be even well expected, where the processes are so complex. According to that experiment, 41,5 grains of nitrous acid gas fill a space equal to 53 cubic inches, and are composed of nearly 29 nitrous gas, and 12,5 oxygene.

We may then conclude, First, that 100 cubic inches of nitrous acid, such as exists in the[24] aëriform state saturated with oxygene, at temperature 55°, and atmospheric pressure 30,1 weigh 75,17 grains.

[24] As is evident from the superabundant quantity of oxygene thrown into the globe.

Secondly, that 100 grains of it are composed of 68,06 nitrous gas, and 31,94 oxygene. Or assuming what will be hereafter proved, that 100 parts of nitrous gas consist of 55,95 oxygene, and 44,05 nitrogene, of 29,9 nitrogene, and 70,1 oxygene; or taking away decimals, of 30 of the one to 70 of the other.

Thirdly, that 100 grains of pale green solution of nitrous acid in water, of specific gravity 1,301, are composed of 50,62 water, and 49,38 acid of the above composition.

VI. Having thus ascertained the composition of a standard acid, my next object was to obtain it in a more condensed state, as it was otherwise impossible to saturate it to its full extent with nitrous gas. But this I could effect in no other way than by comparing mixtures of known quantities of water, and acids of different specific gravities and colors, with the acid of 1,301.

For the purpose of combining my acids with water, I made use of a cylinder about 8 inches long, and,3 inches in diameter, accurately graduated to grain measures, and furnished with a very tight stopper.

The concentrated acid was first slowly poured into it, and the water gradually added till the required specific gravity was produced;[25] the cylinder being closed and agitated after each addition, so as to produce combination without any liberation of elastic fluid.

[25] The weight of the acid poured into the cylinder being known, its specific gravity was known from the space it occupied in the phial. The weight of water being likewise known, the specific gravity of the solution, when the common temperature was produced, was given by the condensation.

After making a number of experiments with acids of different colors in this advantageous way, I at length found that 90 grains of a deep yellow acid, of specific gravity 1,5, became, when mingled at 40° with 77,5 grains of water, of specific gravity 1,302, and of a light green tinge, as nearly as possible resembling that of the standard acid.

Supposing, then, that these acids contain nearly the same relative proportions of oxygene and nitrogene, 100 grains of the deep yellow acid of 1,5, are composed of 91,9 grains true nitrous acid,[26] and 8,1 grains of water.

[26] That is, such as it exists in the aëriform state at 55°. From the strong affinity of nitrous acid for water, we may suppose that this acid gas contains a larger proportion of it than the other gases.

To ascertain the difference between the composition of this acid, and that of the pale, or nitric acid, of the same specific gravity, I inserted 150 grains of it into a small cylindrical mattrass of the capacity of,5 cubic inches, accurately graduated to grain measures, and connected by a curved tube with the water apparatus. After heat had been applied to the bottom of the mattrass for a few minutes, the color of the fluid gradually changed to a deep red, whilst the globules of gas formed at the bottom of the acid, were almost wholly absorbed in passing through it. In a short time deep red vapour began to fill the tube, and being condensed by the water in the apparatus, was converted into a bright green fluid, at the same time that minute globules of gas were given out. As the heat applied became more intense, a very singular phænomenon presented itself; the condensed vapor, increased in quantity, at length filled the curvature of the tube, and when expelled, formed itself into dark green spherules, which sunk to the bottom of the water, rested for a moment, and then resolved themselves into nitrous gas.[27]

[27] This appearance will be explained hereafter.

When the acid was become completely pale, it was suffered to cool, and weighed. It had lost near 15 grains, and was of specific gravity 1,491. 2 cubic inches and quarter of nitrous gas only were collected.

From this experiment evidently no conclusions could be drawn, as the nitrous gas had carried over with it much nitrous acid (in the form of what Dr. Priestley calls nitrous vapor) and was partially dissolved with it in the water.[28]

[28] This phænomenon will be particularly explained hereafter.

To ascertain, then, the difference between the pale and yellow acids, I was obliged to make use of synthesis, compared with analysis, carried on in a different mode, by means of the following apparatus.

VII. To the stop-cock of the upper cylinder of the mercurial airholder, a capillary tube was adapted, bent so as to be capable of introduction into an orifice in the stopper of a graduated phial similar to that employed for mingling acids with water, and sufficiently long to reach the bottom. With another orifice in the stopper of the phial was connected a similar tube curved, for the purpose of containing a fluid, and of increased diameter at the extremity.[29]

50 cubic inches of pure nitrous gas[30] were thrown into the mercurial apparatus. The graduated phial, containing 90 grains of nitric acid, of specific gravity 1,5, was placed on the top of the airholding cylinder, and made to communicate with it by means of the stop-cock and first tube. Into the second tube a small quantity of solution of potash was placed. When all the junctures were carefully cemented, by pressing on the airholder, the nitrous gas was slowly passed into the phial, and absorbed by the nitrous acid it contained; whilst the small quantities of nitrogene evolved, slowly drove forward the solution in the curved tube; from the height of which, as compared with that of the mercury in the conducing tube, the pressure on the air in the cylinder was known.

In proportion as the nitrous gas was absorbed, the phial became warm, and the acid changed color; it first became straw-colored, then pale yellow, and when about 7½ cubic inches had been combined with it, bright yellow. It had gained in weight nearly 3 grains, and was become of specific gravity 1,496.

[29] The outline only of this apparatus is given here, as far as was necessary to make the experiment intelligible; a detailed account of it, and of its general application, will be given in the appendix.

[30] That is, from nitrous acid and mercury.

This experiment afforded me an approximation to the real difference between nitric and yellow nitrous acid; and learning from it that nitric acid was diminished in specific gravity by combination with nitrous gas, I procured a pale acid of specific gravity 1,504.[31] After this acid had been combined in the same manner as before, with about 8 cubic inches of nitrous gas,[32] it became nearly of specific gravity 1,5, and had gained in weight about 3 grains.

[31] A pale acid of 1.52, by being converted into yellow acid, became nearly of specific gravity 15,1.

[32] It is impossible to ascertain the quantity of gas absorbed to more than a quarter of a cubic inch, as the first portions of nitrous gas thrown into the graduated cylinder are combined with the oxygene of the common air in it, to form nitrous acid, and hence the slight excess of weight.

Assuming the accuracy of this experiment as a foundation for calculation, I endeavoured in the same manner to ascertain the differences in the composition of the orange colored acids, and the acids containing still larger proportions of nitrous gas.

93 grains of the bright yellow acid of 1,5 became, when 6 cubic inches of gas had been passed through it, orange colored and fuming, whilst the undissolved gas increased in quantity so much as to render it impossible to confine it by the solution of potash. When 9 cubic inches had passed through, it became dark orange. It had gained in weight 2,75 grains, and was become of specific gravity 1,48 nearly. Hence it was evident that much nitrous gas had passed through it undissolved. 25 cubic inches more of nitrous gas were now slowly sent through it: it first became of a light olive, then of a dark olive, then of a muddy green, then of a bright green, and lastly of a blue green. After its assumption of this color, the gas appeared to pass through it unaltered, and large globules of fluid, of a darker green than the rest, remained at the bottom of the cylinder, and when agitated, did not combine with it. The increase of weight was only 1 grain, and the acid was of specific gravity 1,474 nearly.

In this experiment it was evident that the unabsorbed nitrous gas had carried over with it a considerable quantity of nitrous acid. I endeavoured to correct the errors resulting from this circumstance, by connecting the curved tube first with a small water apparatus, and afterwards with a mercurial apparatus; but when the water apparatus was used, the greater part of the unabsorbed gas was dissolved with the nitrous acid it held in solution, by the water; and when mercury was employed, the nitrous acid that came over was decomposed, and the quantity of nitrous gas evolved, in consequence increased.

As it was possible that a small deficiency of weight might arise from the red vapor given out during the processes of weighing and examining the acid in the last experiment, 35 cubic inches of nitrous gas were very slowly passed through 90 grains of pale nitrous acid, of specific gravity 1,5: it became of similar appearance to that just described, had gained in weight 6,75 grains, and was become of specific gravity 1,475.

These experiments did not afford approximations sufficiently accurate towards the composition of deoxygenated acids, containing more nitrous gas than the dark orange colored. To obtain them, a solution consisting of 94,25 grains of blue green, or perfectly nitrated acid, (if we may be allowed to employ the term), of specific gravity 1,475, was inserted into a graduated phial, and connected by a curved tube, with the mercurial airholder; in the conductor of which a small quantity of water was inserted to absorb the nitrous acid which might be carried over by the gas. Heat was slowly applied to the phial, and nitrous gas given out with great rapidity. When 4 cubic inches were collected, the acid became dark olive, when 9 dark red, when 13 bright orange, and when 18 pale. It had lost 31 grains, and when completely cool, was of specific gravity 1,502 nearly. The water in the apparatus was tinged of a light blue; from whence we may conclude that some of the nitrous gas was absorbed by it with the nitrous acid: but it will be hereafter proved that the orange colored acid is the most nitrated acid capable of combining undecompounded with water, and that the color it communicates to a large quantity of water, is light blue. If then we take 6,1 grains, the quantity of gas collected, from 31 the loss, the remainder is 24,9, which reasoning from the synthetical experiment, may be supposed to contain nearly 3 cubic inches of nitrous gas. Consequently, 94,25 grains of dark green acid, of specific gravity 1,475, are composed of nearly 21 cubic inches, or 7,2 grains of nitrous gas, and 87,05 grains of pale nitrous acid, of 1,504.

VIII. Comparing the different synthetical and analytical experiments, we may conclude with tolerable accuracy, that 92,75 grains of bright yellow, or standard acid of 1,5, are composed of 2,75 grains of nitrous gas, and 90 grains of nitric acid of 1,504; but 92,75 grains of standard acid contain 85,23 grains of nitrous acid, composed of about 27,23 of oxygene, and 58, nitrous gas: now from 58, take 2,75, and the remainder 55,25, is the quantity of nitrous gas contained in 90 grains of nitric acid of 1,504; consequently, 100 grains of it are composed of 8,45 water, and 91,55 true acid, containing 61,32 nitrous gas, and 30,23 oxygene; or 27,01 nitrogene, and 64,54 oxygene: and the nitrogene in nitric acid, is to the oxygene as 1 to 2,389.

IX. My ingenious friend, Mr. JAMES THOMSON, has communicated to me some observations relating to the composition of nitrous acid (that is, the orange colored acid), from which he draws a conclusion which is, in my opinion, countenanced by all the facts we are in possession of, namely, “that it ought not to be considered as a distinct and less oxygenated state of acid, but simply as nitric or pale acid, holding in solution, that is, loosely combined with, nitrous gas.”[33]

[33] In a letter to me, dated Oct. 28, 1799, after giving an account of some experiments on the phlogistication of nitric acid by heat and light, he says, “It was from an attentive examination of the manner in which the nitric acid was phlogisticated in these experiments, that I was confirmed in the suspicion I had long before entertained, of the real difference between the _nitrous_ and _nitric_ acids. It is not enough to shew that in the _nitrous_ acid, (that is, the nitric holding nitrous gas in solution), the proportion of oxygene in the whole compound is less than that entering into the composition of the nitric acid, and that it is therefore less oxygenated. By the same mode of reasoning we might prove that water, by absorbing carbonic acid gas, became less oxygenated, which is absurd. Should any one attempt to prove (which will be necessary to substantiate the generally received doctrine) that the oxygene of the nitrous gas combines with the oxygene of the acid, and the nitrogene, in like manner, so that the resulting acid, when nitrous gas is absorbed by nitric acid, is a binary combination of oxygene and nitrogene, he would find it somewhat more difficult than he at first imagined; it appears to me impossible. It is much more consonant with experiment to suppose that nitrous acid is nothing more than nitric acid holding nitrous gas in solution, which might in conformity to the principles of the French nomenclature, be called nitrate of nitrogene. The difficulty, and in some cases the impossibility, of forming nitrites, arises from the weak affinity which nitrous gas has for nitric acid, compared with that of other substances; and the decomposition of nitrous acid (that is, nitrate of nitrogene) by an alkaline or metallic substance, is perfectly analogous to the decomposition of any other nitrate, the nitrous gas being displaced by the superior affinity of the alkali for the acid.

“Agreeable to this theory, the salts denominated _nitrites_ are in fact triple salts, or ternary combinations of nitric acid, nitrous gas, and salifiable bases.”

This theory is perfectly new to me. Other Chemists to whom I have mentioned it, have likewise considered it as new. Yet in a subsequent letter Mr. Thomson mentions that he had been told of the belief of a similar opinion among the French Chemists.

It is impossible to call any substance a simple acid that is incapable of entering undecompounded into combination with the alkalies, &c; but it will appear hereafter that the salts called in the new nomenclature _nitrites_, cannot be directly formed. If, indeed, it could be proved, that the heat produced by the combination of nitrous acid with salifiable bases, was the only cause of the partial decomposition of it, and that when this process was effected in such a way as to prevent increase of temperature, no nitrous gas was liberated, the common theory might have some foundation; but though dilute phlogisticated nitrous acid combines[34] with alkaline solutions without decomposition, yet no excess of nitrous gas is found in the solid salt: it is either disengaged in proportion as the water is evaporated, or it absorbs oxygene from the atmosphere, and becomes nitric acid.

[34] In some experiments made on the nitrites of potash, and of ammoniac, before I was well acquainted with the composition of nitric acid, I found that a light olive-colored acid of 1,28, was capable of being saturated by weak solutions of potash and ammoniac, without losing any nitrous gas; but after the evaporation of the neutralised solution, at very low temperatures, the salts in all their properties resembled _nitrates_.

In proportion as the nitrous acids contain more nitrous gas, so in proportion do they more readily give it out. From the blue green acid it is liberated slowly at the temperature of 50°, and from the green likewise on agitation. The orange coloured and yellow acids do not require a heat above 200° to free them of their nitrous gas; and all the colored acids, when exposed to the atmosphere absorb oxygene, and become by degrees pale.

If the nitrous vapour, i. e. such as is disengaged during the _denitration_ of the colored acids, was capable of combining with the alkalies, it might be supposed a distinct acid, and called nitrous acid; and the acids of different colors might be considered simply as compounds of this acid with nitric acid; but it appears to be nothing more than a solution of nitric acid in nitrous gas, incapable of condensation, undecompounded, and when decompounded and condensed, constituting the dark green acid, which is immiscible with water,[35] and uncombinable with the alkalies.[36]

[35] As is evident from the curious appearance of the dark green spherules, repulsive both to water, and light green acid.

[36] That is, undecompounded.

It seems therefore reasonable, till we are in possession of new lights on the subject, to consider, with Mr. Thomson, the deoxygenated or nitrous acids simply as solutions of nitrous gas composed of sulphuric acid, metallic oxides, and nitrous gas.[37]

[37] The existence of these bodies will be hereafter proved.

Supposing the truth of these principles according to the logic of the French nomenclature, there is no acid to which the term nitrous acid _ought_ to be applied; but as it has been used to signify the acids holding in solution nitrous gas, it is perhaps better still to apply it to those substances, than to invent for them new names. A nomenclature, accurately expressing their constituent parts, would be too complex, and like all other nomenclatures founded upon theory, liable to perpetual alterations. Their composition is known from their specific gravity and their colors; hence it is better to denote it by those physical properties: thus orange nitrous acid, of specific gravity 1,480, will signify a solution of nitrous gas in nitric acid, in which the nitric acid is to the nitrous gas, nearly as 87 to 5, and to the water as 11 to 1.

X. The estimation of the composition of the yellow and orange colored nitrous acids given in the following table, may be considered as tolerably accurate, being deduced from the synthetical experiments in the sixth section, compared with the analytical ones. But as in the synthetical experiment, when the acid became green, it was impossible to ascertain the quantity of nitrous gas that passed through it unabsorbed, and as in the analysis the quantity of nitrous gas dissolved by the water at different periods of the experiment could not be ascertained, the accounts of the composition of the green acids must be considered only as very imperfect approximations to truth.

TABLE I.

_Containing Approximations to the quantities
of NITRIC ACID, NITROUS GAS, and WATER in
NITROUS ACIDS, of different colors and specific
gravities._
+------------------+---+----------+---+--------+-------+---------+
| 100 | | Specific | | Nitric | Water | Nitrous |
| Parts | | Gravity | | Acid | | gas |
+------------------+---+----------+---+--------+-------+---------+
|Sol. Nitric Acid | | 1,504 | c | 91,55 | 8,45 | — — |
|Yellow Nitrous[38]| | 1,502 | o | 90,5 | 8,3 | 1,2 |
|Bright Yellow | o | 1,500 | n | 88,94 | 8,10 | 2,96 |
|Dark Orange | f | 1,480 | t | 86,84 | 7,6 | 5,56 |
|Light Olive‡ | | 1,479 | a | 86,00 | 7,55 | 6,45 |
|Dark Olive‡ | | 1,478 | i | 85,4 | 7,5 | 7,1 |
|Bright Green‡ | | 1,476 | n | 84,8 | 7,44 | 7,76 |
|Blue Green[39] | | 1,475 | | 84,6 | 7,4 | 8,00 |
+------------------+---+----------+---+--------+-------+---------+
‡ = “FOOTNOTE {38}”

[38] The blue green acid is not homogeneal in its composition, it is composed of the blue green spherules and the bright green acid. The blue green spherules are of greater specific gravity than the dark green acid, probably because they contain little or no water.

[39] The composition of the acids thus marked, is given from calculations.

TABLE II.

_Binary Proportions of OXYGENE and NITROGENE in
NITRIC and NITROUS ACIDS._[40]

+---------------+---+-------+--------+-------------+-------+-------+
| 100 Parts | |Oxygene| Nitro- | | Nitro-|Oxygene|
| | | | gene | | gene | |
+---------------+---+-------+--------+-------------+-------+-------+
|Nitric Acid | c | 70,50 | 29,50 | | 1 | 2,389 |
+---------------+ o +-------+--------+ +-------+-------+
|Bright yellow | n | 70,10 | 29,90 | | 1 | 2,344 |
| Nitrous | t | | |Proportions. | | |
+---------------+ a +-------+--------+ Nitrogene. +-------+-------+
|Orange coloured| i | 69,63 | 30,37 | Unity. | 1 | 2,292 |
+---------------+ n +-------+--------+ +-------+-------+
|Dark Green | | 69,08 | 30,92 | | 1 | 2,230 |
+---------------+---+-------+--------+-------------+-------+-------+

[40] Nitrous gas contains 44,05 Nitrogene, and 55,95 Oxygene, as has been said before.

XI. I have before mentioned that dilute nitric acids are incapable of dissolving so much nitrous gas in proportion to their quantities of true acid, as concentrated ones. During their absorption of it, they go through similar changes of color; 330 grains of nitric acid, of specific gravity 1,36, after 50 cubic inches of gas had been passed through it, became blue green, and of specific gravity 1,351. It had gained in weight but 3 grains; and when the nitrous gas was driven from it by heat into a water apparatus, but 7 cubic inches were collected.[41]