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- Herausgeber: Science & Technology Publishing
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
Researches, Chemical and Philosophical; Chiefly Concerning Nitrous Oxide, or Dephlogisticated Nitrous Air, and its Respiration is a seminal scientific work authored by the renowned chemist Humphry Davy, first published in 1800. This groundbreaking book documents Davy’s extensive experimental investigations into the properties, preparation, and physiological effects of nitrous oxide—commonly known as laughing gas. Through a series of meticulously detailed experiments, Davy explores the chemical composition and reactions of nitrous oxide, its synthesis, and its behavior under various conditions. The book is notable for its vivid descriptions of self-experimentation, as Davy and his colleagues personally inhaled the gas to observe its effects, recording sensations of euphoria, altered consciousness, and pain relief. These observations laid the foundation for the later use of nitrous oxide as an anesthetic in medicine. Davy’s work is not limited to nitrous oxide alone; it also delves into broader chemical and philosophical questions of the era, including the nature of gases, the process of respiration, and the theoretical framework of phlogiston versus the emerging understanding of chemical elements and compounds. The book is structured as a series of essays, experimental reports, and reflective commentaries, providing insight into the scientific methods and intellectual climate of the late 18th and early 19th centuries. Rich with empirical data, personal anecdotes, and theoretical speculation, Researches, Chemical and Philosophical stands as a landmark in the history of chemistry and physiology, showcasing Davy’s innovative spirit and his pivotal role in advancing scientific knowledge.
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RESEARCHES, CHEMICAL and PHILOSOPHICAL;CHIEFLY CONCERNINGNITROUS 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 ofNitric AcidandNitrous Gas, and the production ofNitrous Oxide.
DIVISION I.
ExperimentsandObservationson the composition ofNitric Acid, and on its combinations withWaterandNitrous 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.
ExperimentsandObservationson the composition ofAmmoniacand on its combinations withWaterandNitric 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.
DecompositionofNitrateofAmmoniac—Preparation ofrespirable 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 ofNitrous Oxide, and its decomposition.
DIVISION I.
ExperimentsandObservationson the combinations ofNitrous 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 ofNitrous Oxideby 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 theRespirationofNitrous Oxideandother Gases.
DIVISION I.
ExperimentsandObservationson the effects produced upon Animals by the respiration ofNitrous 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 inNitrous Oxideand 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 theEffectsproduced by theRespirationofNitrous Oxideupon differentIndividuals.
DIVISION I.
Historyof the Discovery.—Effectsproduced by the Respiration of differentGases.
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.
Detailsof the Effects produced by the Respiration ofNitrous Oxideupon 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 ofNitrous Oxide, byDr. 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.
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.
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 ofNITRIC ACIDandNITROUS GAS
and the production ofNITROUS OXIDE.
Pl. I. MERCURIAL AIRHOLDER and BREATHING MACHINE.
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 withWaterandNitrous 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]
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]
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.
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]
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.
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.
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.
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]
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]
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]
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.
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
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.
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.
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.
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]
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]
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.
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.
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]
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.
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]
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]
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.
TABLE II.
Binary Proportions of OXYGENE and NITROGENE in NITRIC and NITROUS ACIDS.[40]
100 Parts
Oxygene
Nitrogene
Nitrogene
Oxygene
Nitric Acid
c
70,50
29,50
1
2,389
o
Bright yellow Nitrous
n
70,10
29,90
Proportions.
1
2,344
t
Nitrogene.
Orange coloured
a
69,63
30,37
Unity.
1
2,292
i
Dark Green
n
69,08
30,92
1
2,230
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]
From the diminution of specific gravity of nitric acid by combination with nitrous gas, and from the smaller attraction of nitric acid for nitrous gas, in proportion as it is diluted, it is probable that the nitrated acids, in their combinations with water, do not contract so much as[42] nitric acids of the same specific gravities. The affinities resulting from the small attraction of nitrous gas for water, and its greater attraction for nitric acid, must be such as to lessen the affinity of nitric acid and water for each other.
Hence it would require an infinite number of experiments to ascertain the real quantities of acid, nitrous gas, and water, contained in the different diluted nitrous acids; and after these quantities were determined, they would probably have no important connection with the chemical arrangement. As yet, our instruments of experiment are not sufficiently exact to afford us the means of ascertaining the ratio in which the attraction of nitric acid[43] for water diminishes in its progress towards saturation.
The estimations in the following table, of the real quantities of nitric acid in solutions of different specific gravities, were deduced from experiments made in the manner described in section VI, except that the phial employed was longer, narrower, and graduated to half grains. The temperature, at the time of combination, was from 40° to 46°.
TABLE III.
Of the Quantities of True NITRIC ACID in solutions of different SPECIFIC GRAVITIES.
100 Parts Acid of specific gravity
True Acid
[44]
Water
1,5040
91,55
8,45
1,4475
c
80,39
19,61
1,4285
o
71,65
28,35
1,3906
n
62,96
37,04
1,3551
t
56,88
43,12
1,3186
a
52,03
47,97
1,3042
i
49,04
50,96
1,2831
n
46,03
53,97
1,2090
45,27
54,73
XII. The blue green spherules mentioned in section V. produced by the condensation of nitrous vapor, and by the combination of nitric acid with nitrous gas, may be considered as saturated solutions of nitrous gas in nitric acid. The combinations of nitric acid and nitrous gas containing a larger proportion of nitrous gas, are incapable of existing in the fluid state at common temperatures; and, as appears from the first experiment, an increase of volume takes place during their formation. They consequently ought to be looked upon as solutions of nitric acid in nitrous gas, identical with the nitrous vapor of Priestley.
From the researches of this great discoverer, we learn that nitrous vapor is decomposable, both by water and mercury. Hence it is almost impossible accurately to ascertain its composition. In one of his experiments,[45] when more than 130 grains of strong nitrous acid were exposed for two days to nearly 247 cubic inches of nitrous gas, over water: about half of the acid was dissolved, and deposited with the gas in the water.[46]
XIII. In comparing the results of my fundamental experiment on the composition of nitrous acid, with those of Cavendish, the great coincidence between them gave me very high satisfaction, as affording additional proofs of accuracy. If the acid formed in the last experiment of this illustrious philosopher be supposed analogous to the light green acid formed in my first experiment, our estimations will be almost identical.
Lavoisier’s account of the composition of the nitric and nitrous acids, has been generally adopted. According to his estimation, these substances contain a much larger quantity of oxygene than I have assigned to them.
The fundamental experiments of this great philosopher were made at an early period of pneumatic chemistry,[47] on the decomposition of nitre by charcoal; and he considered the nitrogene evolved, and the oxygene of the carbonic acid produced in this process, as the component parts of the nitric acid contained in the nitre.
I have before mentioned the liberation of nitrous acid, in the decomposition of nitre by combustible bodies; and I had reasons for suspecting that this circumstance was not the only source of inaccuracy.
That my suspicions were well founded, will appear from the following experiments:
EXPERIMENT a. I introduced into a strong glass tube, 3 inches long, and nearly,3 wide, a mixture of 10 grains of pulverised, well burnt charcoal, and 60 grains of nitre. It was fired by means of touch-paper, and the tube instantly plunged under a jar filled with dry mercury. A quantity of gas, clouded with dense white vapor was collected. When this vapor was precipitated, so that the surface of the mercury could be seen, it appeared white, as if acted on by nitrous acid. On introducing a little oxygene into the jar, copious red fumes appeared.
EXP. b. A similar mixture was fired[48] under the jar, the top of the mercury being covered with a small quantity of red cabbage juice, rendered green by an alkali. This juice, examined when the vapor was precipitated, was become red, and on introducing to it a little carbonate of potash, a slight effervescence took place.
EXP. c. Five grains of charcoal, and 20 of nitre, were now fired in the same manner as before, the mercury being covered with a stratum of water. After the precipitation of the vapor on the introduction of oxygene, no red fumes were perceived.
EXP. d. 30 grains of nitre, 5 of charcoal, and five of silicious earth,[49] were now mingled and fired. The gas received under mercury was composed of 18 carbonic acid, and nearly 12 nitrogene.[50] A little muriatic acid was poured on the residuum in the tube; a slight effervescence took place.
EXP. e. The top of the mercury in the jar was now covered with a little diluted muriatic acid, and a small glass tube filled with a mixture of 3 grains of charcoal, and 20 nitre. After the deflagration, the tube itself with the residuum it contained, were thrown into the jar. The carbonic acid was quickly detached from them by the muriatic acid, and the whole quantity of gas generated in the process, obtained; it measured 15 cubic inches.
4 cubic inches of it exposed to solution of potash, diminished to 1⁴/₁₀; 7 of the remainder, with 8 of oxygene, gave only 12.
EXP. f. 60 grains of nitre, and 9 of charcoal were fired, the top of the mercury in the jar being covered with water. After the deflagration, the tube that had contained them was introduced, and the carbonic acid contained by the carbonate of potash, disengaged by muriatic acid. 30 measures of the gases evolved were exposed to caustic potash; 20 exactly were absorbed, the 10 remaining, with 10 of oxygene, diminished to 17.
EXP. g. A mixture of nitre and charcoal were deflagrated over a little water in the mercurial jar: after the precipitation of the vapor, the water was absorbed by filtrating paper. This filtrating paper, heated in a solution of potash, gave a faint smell of ammoniac.
EXP. h. Water impregnated with the vapor produced in the deflagration, was heated with quicklime, and presented separately to three persons accustomed to chemical odors. Two of them instantly recognised the ammoniacal smell, the other could not ascertain it. Paper reddened with cabbage juice was quickly turned green by the vapor.
These experiments are sufficient to shew that the decomposition of nitre by charcoal is a very complex process, and that the intense degree of heat produced may effect changes in the substances employed, which we are unable to estimate.
The products, instead of being simply carbonic acid, and nitrogene, are carbonic acid, nitrogene, nitrous acid, probably ammonia, and sometimes nitrous gas. The nitrous acid is disengaged from the base by the intense heat. Concerning the formation of the ammonia, it is useless to reason till we have obtained unequivocal testimonies of its existence; it may be produced either by the decomposition of the water contained in the nitre, by the combination of its oxygene with the charcoal, and of its nascent hydrogene with the nitrogene of the nitric acid; or from some unknown decomposition of the potash.
As neither Lavoisier nor Berthollet found nitrous gas produced in the decomposition of nitre by charcoal, when a water apparatus was employed; and as it was not uniformly evolved in my experiments, the most probable supposition is, that it arises from the decomposition of a portion of the free nitrous acid intensely heated, by the mercury.
In none of my experiments was the whole of the nitre and charcoal decomposed, some of it was uniformly thrown with the gases into the mercurial apparatus. The nitrogene evolved, as far as I could ascertain by the common tests, was mingled with no inflammable gas.
If we consider experiment f as accurate, with regard to the relative quantities of carbonic acid and nitrogene produced, they are to each other nearly as 20 to 8; that is, allowing 2 for the nitrous gas, and consequently, reasoning in the same manner as Lavoisier, concerning the composition of nitric acid, it should be composed of 1 nitrogene to 3,38 oxygene. But though the quantity of oxygene in this estimation is far short of that given in his, yet still it is too much. From whatever source the errors arise, whether from the evolution of phlogisticated nitrous acid, or the decomposition of water, or the production of nitrous gas, they all tend to increase the proportion of the carbonic acid to the nitrogene.
I am unacquainted with any experiment from which accurate opinions concerning the different relative proportions of oxygene and nitrogene in the nitric and nitrous acids could be deduced. Lavoisier’s calculation is founded on his fundamental experiment, and on the combination of nitrous gas and oxygene.
Dr. Priestley’s experiment mentioned in section 12, on the absorption of nitrous gas by nitrous acid, from which Kirwan[51] deduces the composition of the differently colored nitrous acids, was made over water, by which, as is evident from a minute examination of the facts[52], the greater portion of the nitrous gas employed was absorbed.
XIV. The opinions heretofore adopted respecting the quantities of real or true acid in solutions of nitrous acid of different specific gravities, have been founded on experiments made on the nitro-neutral salts, the most accurate of which are those of Kirwan, Bergman, and Wenzel. The great difference in the results of these celebrated men, proves the difficulty of the investigation, and the existence of sources of error.[53] Kirwan deduces the composition of the solutions of nitrous acid in water, from an experiment on the formation of nitrated soda. In this experiment, 36,05 grains of soda were saturated by 145 grains of nitrous acid, of specific gravity 1,2754. By a test experiment, he found the quantity of salt formed to be 85,142 grains.[54] Hence he concludes that 100 parts of nitrous acid, of specific gravity 1,5543, contain 73,54 of the strongest, or most concentrated acid.
Supposing his estimation perfectly true, 100 parts of the aëriform acid of 55° would be composed of 74,54 of his real acid, and 25,46 water. In examining, however, one of his later experiments,[55] we shall find reasons for concluding, that the acid in nitrated soda cannot contain much less water than the aëriform acid. A solution of carbonated soda, containing 125 grains of real alkali, was saturated by 306,2 grains of nitrous acid, of specific gravity 1,416. The evaporation was carried on in a temperature not exceeding 120°, and the residuum exposed to a heat of 400° for six hours, at the end of which time it weighed 308 grains. Now according to my estimation, 306 grains of nitric acid, of 1,416, should contain 215 true acid; and we can hardly suppose, but that during the evaporation and consequent long exposure to heat, some of the nitrated soda was lost with the water.
Bergman estimates the quantity of water in this salt at 25, and the acid at 43 per cent; but his real acid was not so concentrated as Kirwan’s, consequently the nitric acid in nitrated soda should contain more water than my true acid.
