APPENDIX.
No. I.
Effects of Nitrous Oxide on Vegetation.
In July 1799, I introduced two small plants of spurge into nitrous oxide, in contact with a little water over mercury; after remaining in it two days, they preserved their healthy appearance, and I could not perceive that any gas had been absorbed. I was prevented by an accident, from keeping them longer in the gas.
A small plant of mint introduced into nitrous oxide and exposed to light, in three days became dark olive and spotted with brown; and in about six days was quite dead.—Another similar plant, kept in the dark in nitrous oxide, did not alter in color for five days, and at the end of seven days, was only a little yellower than before. I could not ascertain whether any gas had been absorbed.
I introduced into nitrous oxide through water, a healthy budding rose, thinking that its colors might be rendered brighter by the gas. I was disappointed, it very speedily faded and died; possibly injured by the solution of nitrous oxide in water.
Of two rows of peas just appearing above ground; I watered one with solution of nitrous oxide in water, and the other with common water daily, for a fortnight. At the end of this time, I could perceive no difference in their growth, and afterwards they continued to grow equally fast.
I introduced through water into six phials, one of which contained hydrogene, one oxygene, one common air, one hydrocarbonate, one carbonic acid, and one nitrous oxide, six similar plants of mint, their roots being in contact with water and their leaves exposed to light.
The plant in carbonic acid began to fade in less than two days, and in four was dead. That in hydrogene died in less than five days; that in nitrous oxide did not fade much for the first two days, but on the third, drooped very much, and was dead at the same time as that in hydrogene. The plant in oxygene for the first four days, looked flourishing and was certainly of a finer green than before, gradually however, its leaves became spotted with black and dropped off one by one, till at the end of ten days they had all disappeared. At this time the plant in common air looked sickly and yellow, whilst that in hydrocarbonate was greener and more flourishing than ever.
I have detailed these experiments not on account of any important conclusions that may be drawn from them; but with a view of inducing others to repeat them, and to examine the changes effected in the gases. If it should be found by future experiments, that hydrocarbonate generally increased vegetation, it would throw some light upon the use of manures, containing putrefying animal and vegetable substances, from which this gas is perpetually evolved.
The chemistry of vegetation though immediately connected with agriculture, the art on which we depend for subsistence, has been but little investigated. The discoveries of Priestley and Ingenhousz, seem to prove that it is within the reach of our instruments of experiment.
No. II.
APPROXIMATIONS TO THE
Composition and Weight of the aëriform
COMBINATIONS of NITROGENE
At temperature 55°, and atmospheric pressure 30.
| 100 Cubic In. | grains | Nitrogene | Oxygene | ||||
|---|---|---|---|---|---|---|---|
| N | With oxygene | Nitrogene | 30.04 | 100 grains are composed of | |||
| i | Oxygene | 35.06 | |||||
| t | Atmospher. air | w | 31.10 | 73.00 | 27.00 | ||
| r | Nitrous oxide | e | 50.20 | 63.30 | 36.70 | ||
| o | Nitrous gas | i | 34.26 | 44.05 | 55.95 | ||
| g | Nitric acid | g | 76.00 | 29.50 | 70.50 | ||
| e | h | Nitrogene | Hydrogene | ||||
| n | With hydrogene | Ammoniac | 18.05 | 80.00 | 20.00 | ||
| e | |||||||
No. III.
Additional Observations.
a. In [Res. 1st. Div. IV. Sect. III]. in the analysis of nitrous gas by pyrophorus, as no absorption took place when the residual nitrogene was exposed to water, I inferred that if any carbonic acid was formed it was in quantity so minute, as to be unworthy of notice. A few days ago, I compleatly decomposed a quantity of nitrous gas by pyrophorus, when the residual nitrogene was exposed to solution of strontian, the fluid became slightly clouded; but no perceptible absorption took place.
b. If there was the least probability in any of Dr. Girtanner’s speculations on the composition of Azote,[235] the experiments on the exhausted capacity[236] of the lungs in Res. III. might be supposed inconclusive. But there appears to be no more reason for supposing that hydrogene is converted into nitrogene by respiration, than for supposing that it is converted into water, carbonic acid or oxygene; for all these products are evolved when that gas is respired. From the comparison of Exp. 1 with Exp. 3, [Res. iii. Div. ii. Sec. 4], it is almost demonstrated that no ascertainable change is effected in hydrogene by respiration. The experiment of the accurate Scheele in which hydrogene after being respired thirty times in a bladder wholly lost its inflammability, may be easily accounted for from its mixture with the residual gases of the lungs.
About a fortnight ago, I respired, after forced voluntary exhaustion of my lungs, my nose being accurately closed, three quarts of hydrogene in a silk bag, at four intervals, for near five minutes. After this it was highly inflammable, and burnt with a greenish white flame in contact with the atmosphere; but was not so explosive as before.[237]
c. From what we have lately heard of the curious experiments of Mr. Volta and Mr. Carlisle, it is very probable that the conversion of nitrous gas into nitrous oxide when exposed to wetted zinc, copper and tin, in contact with mercury, as described in [Res. I. Div. V]. may in some measure depend on the action of the galvanic fluid. Whilst I was engaged in the experiments on this conversion, Dr. Beddoes[238] mentioned to me some curious facts noticed by Humboldt and Ritter, relating to the oxydation of metals by the decomposition of water, which induced me to examine the phænomena with more attention than I should have otherwise done.—I recollect observing that some of the wetted zinc filings in nitrous gas on the side of the jar not in contact with the surface of mercury, were very slowly oxydated. Whilst on the surface of the mercury where small globules of that substance were mingled with the filings of zinc, the decomposition went on much more rapidly; possibly through the medium of the moisture, a series of galvanic circles were formed.
d. In [Res. II. Div]. I. it is stated, that nitrous oxide during its solution by common water, expels about ¹/₁₆ of atmospheric air the volume of the water being unity.
From the delicate experiments of Dr. Pearson, on the passage of the electric spark through water, it appears however probable, that much more than ¹/₁₆ of atmospheric air is sometimes held in solution by that fluid,[239] possibly the whole of the air is not expelled by nitrous oxide, owing to some unknown law of saturation by which an equilibrium of affinity is produced, forming a triple compound.
No. IV.
DESCRIPTION OF A MERCURIAL AIRHOLDER.
Suggested by an inspection of Mr. Watt’s Machine for containing Factitious Airs.
By WILLIAM CLAYFIELD.
Several modes of counteracting the pressure of a decreasing column of mercury having been thought of in conjunction with Mr. W. Cox, the following was at last adopted as the most simple and effectual.
[Plate 1 Fig. 1], represents a section of the machine, which consists of a strong glass cylinder A cemented to one of the same kind B, fitted to the solid block C, into which the glass tube D is cemented for conveying air into the moveable receiver E.
The brass axis [F, Fig. 2], having a double bearing at a, a, is terminated at one end by the wheel G, the circumference of which is equal to the depth of the receiver, so that it may be drawn to the surface of the mercury by the cord b in one revolution; to the other end is fitted the wheel H, over which the balance cord c runs in an opposite direction in the spiral groove e, a front view of the wheel H is shewn at [Fig. 3].
Having loaded the receiver with the weight I, something heavier than may be necessary to force it through the mercury, it is balanced by the small weight K, which hangs from that part of the spiral where the radius is equal to that of the wheel G, from this point the radius of the spiral must be increased in such proportion, that in every part of its circuit, the weight K may be an exact counterpoise to the airholder. In this way, so little friction will be produced, that merely plunging the lower orifice of the tube D under mercury contained in the small vessel L, will be sufficient to overcome every resistance, and to force the gas discharged from the beak of a retort into the receiver, where whatever may be its quantity, it will be subjected to a pressure exactly corresponding to that of the atmosphere. The edge of the wheel H being graduated, the balance cord c may be made to indicate its volume.
Should it at any time be necessary to reduce the pressure to the medium standard of the barometer, it may easily be done by graduating the lower end of the tube D, and adding to the weights I or K, as may be found necessary; the surface of the mercury in the tube pointing out the increase or diminution.
The concavity at the top of the internal cylinder is intended to contain any liquid it may be thought proper to expose to the action of the gas.
The upper orifice f, with its ground stopper, is particularly useful in conveying air from the retort g, with its curved neck, into the receiver, without its passing through the tube D. In all cases where a rapid extrication of gas is expected the retort g, should be firmly luted to the orifice and the weight I, removed from the top of the receiver, this by diminishing the pressure, will admit the gas to expand freely in the airholder at the instant of its formation, and prevent an explosion of the vessels. The same caution must be observed whenever any inflammation of gas is produced by the electric spark.
The air may be readily transferred through water or even mercury by the tube h, [Fig. 1].
To prevent an absorption of mercury in case of a condensation taking place in the retort made use of for generating air, Mr. Davy has applied the stop-cock i, to which the neck is firmly luted. This stop-cock is likewise of great service in saturating water with acid or alkaline gases, which may be effected by luting one end of the tube k to the stop-cock, and plunging the other into the fluid in the small vessel l, cemented at top, and terminating in the bent funnel m—the tube h having been previously removed, and the lower orifice of the tube D either sunk to a considerable depth in mercury, or closed with a ground stopper. The bend of the funnel m, may be accurately closed by the introduction of a few lines of mercury.
The application of the stop-cock n, has enabled Mr. Davy to perform some experiments on respiration with considerable accuracy.
Note. This apparatus was first described in the third part of Dr. Beddoes’s Considerations; its relation to Mr. Davy’s experiments with the improvements it has lately received, may probably be deemed sufficient to excuse the re-printing it.—The weight I. [Fig. 2], having been omitted in the plate, the reader must supply the deficiency.
W. C.
PROPOSALS
FOR THE PRESERVATION OF
ACCIDENTAL OBSERVATIONS
IN
MEDICINE.
In times beyond the reach of history, the medicinal application of substances could have arisen from no other source than accident. Among articles of the materia medica of known origin, we are indebted to accident for some of the most precious.
Accident is every day presenting to different individuals the spectacle of phænomena, arising from uncommon quantities of drugs on the one hand, and on the other, from uncommon conditions of the system, where ordinary powers only have been knowingly or recently applied. What is said of drugs may be extended to natural agents and mental affections.
From conversation with a variety both of medical practitioners and unprofessional observers, the author of this proposal is persuaded that such authentic occurrences only, as have presented themselves to persons now living would, if they could be brought together, compose a body of fact, so instructive to the philosopher, and useful to the physician, that he despairs of finding a term worthy to characterize it.
In some cases, the influence of unsuspected powers would be detected. In others, resources available to the purpose of restoring health in desperate situations would be directly presented, or could be detected by a short and easy process of reasoning. Some anomalous observations, by shewing the absence or agency of contested causes, would perform the office of experimenta crucis—Unusual affections occur of which an exact account would be among the means of removing from physic its opprobrious uncertainty: for this uncertainty frequently depends upon our inability to distinguish the subtler differences in cases which resemble each other in their grosser features.
No striking fact can be accurately stated, in conjunction with its antecedent and concomitant circumstances, without improving our acquaintance with human nature. Our acquisitions in this most important branch of knowledge, may be compared to a number of broken series, of which we have not always more than one or two members. But every new accession bids fair to fill up some deficiency; and a large supply would contribute towards connecting series apparently independent, and working up the whole into one grand all-comprehending chain.
There are complaints, and those by far too frequent, where no known process has a claim to the title of remedial. Here the whole chance of preservation depends on the physician’s capacity for bringing together facts that have heretofore stood remote. But no power of combination can avail where there are no ideas to combine.
Every new observation therefore, may be considered as a standard trunk, sending forth analogies as so many branches crowned with blossoms, some of which cannot fail to be succeeded by salutary fruits. And were it not absurd to extend the illustration of so plain a point, it might be added, that when by the continual interposition of new trunks, the branches are brought near together, the produce of each will be ennobled by the action of their respective principles of fecundation.
Whenever the author has been able to obtain certain information concerning any unusual appearance in animal nature, it has been his custom to preserve it; and among his papers he has memorandums which prove that to our present circumscribed ideas concerning the dose of medicines may be sometimes imputed failures in practice; that certain signs are not to be taken in the received signification; and that many measures are adopted or omitted to the detriment of invalids, because it is assumed that circumstances are necessarily connected which may exist separately, or that one given natural operation is inconsistent with another, to which it may really be synchronous or next in order.
Assiduous observation of the daily states of the human microcosm will be the unfailing consequence of attention to its striking phænomena. Such is the progress of curiosity. Such the origin of all the sciences. The more uniformly clear the sky under which they tended their flocks, the less likely were the shepherds of Chaldæa, to found the science of the stars. And however the disposition to study astronomy might have been strengthened by the coincidence between the heliacal rising of Sirius and the overflowing of the Nile, it must, I conceive, have been awakened by the aspect of meteors and eclipses.
Whatever minute and authentic information this imperfect statement may produce, as soon as it shall amount to a certain mass, the author will present it to the public arranged. He flatters himself that no correspondent will eke out by supposition the defect of genuine observation, without clearly distinguishing the one from the other. He still more confidently hopes that none will be instigated by this advertisement to exercise his invention in the manner of Psalmanasar and Chatterton. Whether any literary forgery can be innocent is questioned—but a forged medical report is a drawn dagger which the arm of a credulous physician may any day plunge into the heart of his defenceless patient. The author has heard some inconsiderate wits avow, that they have transmitted to the venders of quack medicines imaginary cures, attested by fictitious signatures; and it is not without apprehension from the propensity of men to display ingenuity and to relate wonders that he announces the present design. But he shall be on his guard, and hopes to baffle attempts at imposition.
THOMAS BEDDOES.
Rodney-Place, Clifton, June 1800.
END.