Imágenes de páginas
PDF
EPUB

ART. VIII.-The Gas Blow-pipe, or Art of Fusion, by burning

the Gaseous Constituents of Water : giving the History of the Philosophical Apparatus so denominated; the proofs of Anal gy in its operations to the Nature of Volcanoes ; together with an Appendix, containing an Account of Experiments with this Blow-pipe. By Edward Daniel Clarke, LL.D. Professor of Mineralogy in the University of Cambridze, Member of the Royal Academy of Sciences, at Berlin, &c. 8vo. pp. 109. London. 1819. TF the converse of the proposition Mega B.Envov, ueya XOXOV, I were true, we might welcome this little tract, as the production of a writer who, in this instance, at least, has endeavoured, in the words of Addison, to practise in the chemical method, and give the virtue of a full draught in a few drops.'—But, alas ! it has been cast among the chemists, to whom it is more particularly addressed, as the apple of discord was cast among the gods, and set them together by the ears!

The opinion of Macquer, that • There does not exist in nature any substance which may be considered as essentially and vigo. rously infusible.'* is as old as the time of Theophrastus.t When that eloquent philosopher delivered lectures in the Lyceum at Athens, as the successor of Aristotle, the number of his auditors amounted to two thousand; and that they were instructed in many facts considered as of modern discovery, may be seen by reference to the very small part of his writings which has descended to our time. His observations shew that he had attended as carefully to the changes which bodies sustain in consequence of the action of heat as if he had been acquainted with the use of the common blow-pipe. He notices an opinion which had been maintained in Greece, that all stones, excepting marble, were fusible, I and holds this to be true of the greater number; and it is a very remarkable confirmation of the exception he made respecting the carbonate of lime, that-after 'a lapse of above two thousand years, with all the aid afforded by the advancement of science-if a chemist were asked what substance more than any other resists the action of heat, he would adduce the purest carnonate of lime, in the example of Iceland spar, the fusion of which can hardly be effected even by the gas blow-pipe.

An ardent and insatiable curiosity in chemists has in every age prompted them to augment, by every means in their power, the

* Macquer, Dictionnaire de Chimie, article Apyre.
+ Theophras:us [lgpı tav nitat Bibcov x' p. 8 L. Bat. 1647.

# oido sat onas norsci mavras Tnxe bad, TAME Te usou RAX*. T. .-Theophrast. ubs supra.

action of beat; the difficulty of melting some substances having always presented obstacles to metallurgists, and tended greatly to retard many important improvements in the arts. It is foreign to the undertaking we have in view, or it might be easy to shew with what perseverance the ancient alchemists so long laboured in pursuit of an universal solvent for all bodies. This solvent is now found, since there is no substance whatsoever that is not capable of being held in solution by the fluid matter of heat. A series of brilliant experiments, resulting from the discovery of oxygen gas, by Priestley* and Scheele, has gradually led to the introduction and use of the 'gas blow-pipe, or Art of Fusion, by burning the Gaseous Constituents of Water,' by means of which the most refractory bodiest may be melted, and in many instances, entirely volatilized. · As to many of our readers the subject is altogether new, and very important facts are likely to accrue to the science of chemistry, from the further use of the extraordinary means of decomposition offered by the philosophical apparatus here alluded to, we shall endeavour to inake them acquainted with its real nature by a brief description of the instrument itself, before we proceed to state the effects produced by it.

This blow-pipe, literally calculated for setting the Thames on fire,' consists of a small square box, usually made of thick sheet copper, into which, by means of a piston, are compressed the gaseous constituents of water ;f afterwards, by turning a stopcock, the mixed gases are allowed to escape through the narrow aperture of a capillary tube z of an inch in diameter, and exposed to combustion at the orifice, by lighting the gaseous mixture, exactly as we light a common gas lamp. A small flame continues to burn at the extremity of the jet of the tube, to whose powerful heat are exposed all substances submitted to the test of this blow-pipe. Dr. Clarke has devised an apparatus, represented in a frontispiece to the volume, by means of which a continual supply of the gaseous mixture may be forced into the reservoir during the most protracted experiments; the machine is also supplied with a safety cylinder invented by his friend, Professor Cumming, to prevent the consequences of explosion.

The first account of Dr. Clarke's experiments with this blowpipe appeared in the Journal of the Royal Institution, No. III.

# In August, 1774. Scheele discovered the same gas in 1777, without any previous knowledge of what Dr. Priestley had done. Lavoisier first gave it the oame of Orygen Ous.

† The fusion even of charcoal has been accomplished by it.

| Mixed in the proportion of two parts by bulk of hydrogen gas, and one part of oxygen gas.

Some Some of the results of those experiments were afterwards disputed, and various claims were made to the originality of the invention by which they had been conducted; but it is somewhat remarkable that while these claims and disputes continue to be agitated, the author of the work now before us is the only person who has appropriated the instrument itself to any purpose of public utility. During four years which have elapsed since he commenced his experiments with this blow-pipe, he has persevered in exbibiting to the members of the university, before whom he delivers his public lectures, a repetition of those experiments; confirming the truth of them by daily appeals to their testimony, as to the facts which they substantiate. The object of the present publication is, therefore, to shew the utility and safety of the apparatus employed; to point out the progressive steps by which it has been brought to its present state of improvement; the share which the author himself had in the invention ; and the proofs which the instrument has afforded of analogy in its operations to the nature of volcanoes ; that is to say, in its power of fusion ; the means whereby this fusion is accomplished; the result of the coinbustion of the mixed gases, forming water; and the detonations and explosions to which the same com. pressed gaseous mixture is liable.--The subject is curious, and the author shall speak for himself.

· The present observations relate to the Gas Blow-pipe as used for burning a compressed mixture of hydrogen and oxygen gases, when propelled from a common reservoir. The first usage of these gases in a state of mixture, was believed to have been made by an unknown native of Germany; who employed for this purpose a bladder to which a capillary tube was affixed. The author received this information, upon report, after he began to write the account of his own experiments ; but no one has since laid claim to the experiment, nor does he now know whether there be any truth in the rumour. He has been, however, the more anxious to repeat it ; because upon the truth of it depend all pretentions to priority of invention, Dr. Thomas Thomson, now professor of chemistry at Glasgow, made experiments with the mixed gases, at Edinburgh, seventeen years ago ; but was induced to abandon the undertaking, owing to the accidents which happened to his apparatus. With respect to the application of hydrogen and oxygep gases to aid the operations of the blow-pipe, when pro. pelled from different reservoirs through different apertures, by means of hydrostatic or other pressure, the contrivance is as old as the time of Lavoisier. The American chemists lay claim to it, as their inven. tion, in consequence of experiments made, in 1802, by Mr. Robert Hare, junior, professor of Natural Philosophy in Philadelphia ; of which an account appeared in Dr. Bruce': Mineralogical Journal*,

[blocks in formation]

and also in the Annales de Chimie.* Much about the same time, Dr. Thomson also carried on a series of experiments in the same way;f and we have witnessed similar experiments, for at least a dozen years, during the chemical lectures delivered in the University of Cambridge. The combustion of the diamond was always thus exhibited : and in America this plan is still pursued ; that is to say, the two gases are propelled from different reservoirs, and througb different apertures. But the intensity of the heat is incomparably greater when the gases, after compression, are propelled and burned in a mixed state ; because the due proportion necessary for forming water is then constantly and equally maintained: whereas an excess, either on the side of the bydrogen or of the oxygen, not only tends to diminish the temperature, but, if it be much increased on the side of the oxygen, infallibly extinguishes the fame.

*As this method of aiding the operations of the blow pipe differs, in this essential particular, from every other hitherto employed, it is that to which (with all the improvements since made for insuring the safety of the operator the name of the Gas Blow-pipe is now applied, and whose bistory it is the author's present purpose to relate. And this induces a second part of the inquiry ; namely, wbat first suggested the propriety of mixing the two gases in the relative proportion for forming water? because, upon the observance of this proportion the intensity of the heat mainly depends.

• This circumstance was briefly stated in the first account which the author published of his experiments with the gas blow-pipe; but the phænomena upon which it was founded, bigbly interesting as they are, do pot seem to have met with that attention from scientific men to which they are entitled ; probably owing to the very short time usually bestowed by scientific travellers amidst the scenes where such phænomena are fearfully displayed. The author alludes to the phænomena attendant upon volcanoes ; the discomposition of water by volcanic fire; the compression to which the gaseous result is liable ; its subsequent combustion ; the power of fusion it exbibits ; and, lastly, the horrible explosions which take place, whenever the whole of the compressed gas is exposed to combustion. If this happen, as it is well known, whole mountains are blown into the air by the tremendous violence of the explosion, which is heard to the distance of many leagues ; and the eruption ceases. But the minor explosions, or detonations, taking place at the mouths of narrow apertures in a volcano whence liquid rocks are ejected in the form of lava, are such as to resemble the loudest artillery in these cases, a partial explosion of the gaseous mixture takes place ; exactly corresponding with the detonations which, upon a small scale, are heard at the oritice of the jet of the gas blow-pipe; and bearing about the same comparison to the explosion of the gas reservoir, which the detonations at the mouth of a stream of lava do to the explosion of all the pent gas within the volcano. Vesuvius,

* see tom. xlv. p. 113. • Mémoire sur l'Usage du Chalumean, et les Moyens de l'alimenter d' Air,' &c. + This is also stated in the Letter above mentioned,

perhaps,

perhaps, better than any other volcano, may serve to illustrate what is here advanced : because it is better adapted for examination than Ætna, or any other volcano where the crater is remote from the syringes or jets through which the lava is propelled. This mountain, as to its chemical nature, is, in all respects, a vast gas blow-pipe ; corresponding, in all its phænomena, with the appearances and effects, the explosions and detonations, the heat and the light, * exhibited by the apparatus which bears this name ; and differing from it only as the mighty operations of nature in the universe differ from the puny imitations of the chemist in his laboratory. During twelve years that the author has delivered public lectures, in the University of Cambridge, as it is well known to persons who have attended those lectures, he has constantly thus explained the nature and effects of volcanic eruptions. Without the agency of water and its decomposition, these eruptions do not take place. Before any great eruption of Vesuvius, not only does the water disappear in all the wells of Naples, Portici, Resina, and other towns at the foot of the mountain, but even the sea retires; and marine animals, abandoned by their native element, expire upon the shore.'

Dr. Clarke then proceeds to verify these observations by a reference to the phænomena which accompanied the rising of the Monte Nuovo, out of the Lucrine lake, near Naples, and to others of which he was an eye-witness upon Mount Vesuvius; and afterwards relates the inferences deduced from those appearances as they were rendered applicable to the gas blow-pipe.

• Consequently, to imitate the power of fusion exbibited by a volcano, nothing more was necessary than to burn the gaseous constituents of water under similar circumstances ; but here was the difficulty. Every clap of thunder in the atmosphere is sufficient to prove what the consequences are, where the gaseous constituents of water, when in a mixed state, become ignited, even by an electric spark : and who would ven. ture to communicate flame to such a mixture, under compression, for purposes of experiment? The experiments which took place under Lavoisier at Paris and all over Europe, for the composition of nater were an approximation towards it ; because these experiments first proved that the gaseous constituents of water might be used to aid the operatious of the blow-pipe. It was then, in fact, first made known, that the two gases, when burned separately, and propelled from different reservoirs, through different apertures, by hydrostatic pressure, towards one point (which was the method afterwards pursued by Professor Hare in America), exbibited a degree of temperature capable of effecting THE COMBUSTION OF THE Diamond! Therefore, if it be requisite to trace the invention of the gas blow-pipe to the first principles which led to the whole of the contrivance, it is to these discoveries of Laroisier

*. There is no other way in which any idea cap be given of the intense light beaming from the source of a stream of perfectly liquid lava, than by attending to the fusion of the most refractory substances before the gas blow-pipe, which exbibits an emanation of the same kind of light, comparatively, as the light of a star, to that of the sun.

that

« AnteriorContinuar »