162 WEEKES'S UNIVERSAL PORTABLE EUDIOMETER. MEMOIR, DESCRIPTIVE OF AN UNIVERSAL PORTABLE EUDIOMETER, ITS CONSTRUCTION, AND MODEs of use. By W. H. Weekes, Esq., Surgeon, Lecturer on Chemistry and Experimental Science to the Canterbury Philosophical and Literary Institution, &c. "How immense is the empire of chemistry! It embraces in its studies all the phenomena which nature presents to our view, in the infinite variety of her productions, and all the processes of the arts for which we are indebted to human ingenuity."-CHAPTAL. "The person who could devise only, without knowing how to perform, would not be able to extend his knowledge far, or make it useful; and where every doubt or question that arises in the mind is best answered by the result of an experiment, that which enables the philosopher to perform the experiment in the simplest, quickest, and most correct manner, cannot but be esteemed by him as of the utmost value."-FARADAY. The progress of experimental inquiry, which, happily for the interests of the civilised world, towards the close of the last, and more particularly during the present century, has taken a deep and salutary hold upon the affections of mankind, is awakening the most dormant and energetic spirits from the slumber of a benighted ignorance, and an apathetic indifference to the importance of philosophical research. It is not here necessary to dilate upon the vast acquisitions obtained from this happy exten sion of the powers of mind, over the multitudinous forms of matter, through the agency of practical inquiry; it is enough that the genuine philanthropist is enabled to glance with retrospective satisfaction over the beneficial results which science has already effected, while his ardent mind brightens with the operations of the present, and expands with the joy of a generous enthusiasm, as the prospects of the future unfold themselves to the eye of intellectuality. Amidst the splendid scenery with which philosophy has decorated man's theatre of action, none, perhaps, has been arrayed in brighter vestments, or shone with a more resplendent lustre, reflected from a thousand arts and manufactures, than the science of chemistry; holding, as it does, a talisman, the potency of which unlocks nature's most secret cabinets, and from thence displays, alike to the philosopher and the artisan, the hidden properties of the whole material world. This science is, of necessity, when it arrives at legitimate conclusions, wholly experimental; and as a constant succession of new facts are created by experiment, the occasion arises for modifying and extending operative power. Hence the advantage and convenience of simplifying and improving the varied forms of apparatus, necessary for the multifarious purposes of the philosophical chemist; and the importance of increasing his power over matter by a skilful addition to his means of subduing and regulating its various forms, by the introduction of new species of instrumental agency. It may justly be doubted, whether, without the enormous voltaic battery employed by the illustrious Davy, we should now have to congratulate ourselves on an acquaintance with the metallic basis of the alkalies; or, unaided by the immense, and as yet incalculable, intensity of the oxy-hydrogen blow-pipe, have been led, even to entertain a suspicion that the earths, too, are but oxides of a similar modification of matter. The possession of a new instrument, has, in the hands of the man of science, not unfrequently led to the creation of new pursuits, independent of the facility it has yielded to the development of facts not previously recognised in the annals of scientific inquiry; and to the importance of enlarging, and advancing the means of research, the eminent names that have shed abundant lustre on continental science, and especially the savans of the French capital, appear to have been equally alive with ourselves. In submitting to the scientific world a new form of instrument, which has been found eminently advantageous in the delightful department of pneumatic chemistry, a certain degree of diffidence, perhaps, properly attends its introduction; but, without subjecting myself to a charge of egotism, I may be allowed to remark, that though the apparatus, forming the subject of the following "Memoir," has been employed by myself in a long and extensive series of experiments, both for the purpose of trial, and with a view to chemical research, I have not found it advisable to effect any material alteration with an eye to improvement, nor have I felt the slightest inducement to exchange its use for that of any other instrument with which I have the pleasure to be acquainted, WEEKES'S UNIVERSAL PORTABLE EUDiometer. though I should be sorry to be deemed insensible to the merits of several, which are well known to the philosophical world. As, however, inventors may be naturally supposed to evince a strong partiality for the result of their own schemes, I have aimed to put a check upon feelings of this description, by availing myself of every opportunity to bring the operation of the instrument under the inspection of such scientific minds as have been willing to oblige by their attention; and, though the merits or demerits of every invention necessarily ought to abide the ordeal of repeated experiment, upon which the legitimate tribunal of science is erected, 1 feel no small gratification in the concurrent opinions which have been expressed in regard to the utility and advantages of the Universal Portable Eudiometer, while I rely with earnestness upon the rectitude of future decision. Description of the Universal Portable Eudiometer. The philosophical apparatus to which the title of Universal Portable Eudiometer has been applied, is perhaps not destitute of such claims as may, on experience of its use, sanction the application of the term, which the inventor has been induced to adopt more from a conviction of its being expressive of the principle and application of the instrument, than otherwise. The eudiometer, which we are now to describe, is applicable to the purpose of chemically examining gaseous mixtures, by detonation with the electric spark, as in the eudiometers of Volta and others, or by absorption, upon the principle of the instrument invented and described by Dr. Hope; and equally so, as regards the former case, whether the gases require to be operated upon over water or mercury; nor is the use of the pneumatic trough, which is indispensable to other instruments of this denomination, at all necessary in either case. The apparatus may be regarded, to a considerable degree, as a self-acting instrument, charging itself with gas, and regulating the volume to be operated upon, by the mere turning and management of a small stop-cock. In the ordinary modes of analysis, dependent on the presence of definite portions of oxygen, and detonation of the 163 gaseous mixture by the agency of electricity, it is necessary to transfer the gases under examination, from their respective bladders, or gas-holders, by means of a curved pipe, into the eudiometer tube, as it stands over the fluid of a pneumatic trough, which is often a tedious, and sometimes an uncertain operation, as regards the quantities intended for admixture. This inconvenience is completely obviated in the apparatus under consideration, by the attachment of a small reservoir, containing the explosive mixture, placed closely in contiguity, and communicating directly with the tube of detonation, and which, though perfectly secure from accident, during the transit of the electric spark, may be instantaneously removed or not, dependent on the choice of the operator. In all manipulations with this eudiometer, a security is effected against the escape of any portion of the gaseous mixture, so frequently incidental on its enlargement of volume, at the instant of its decomposition, when the common eudiometer is employed; while, by means of the instrument of which we are treating, that enlargement of volume is accurately measured, and the amount registered, so as to be read off with facility by the experimentalist; as is also the residual gas, when there is any, in the tube of detonation. As it is not to be apprehended that any of the fluid, necessary to be employed in the several manipulations, can be thrown about, as in the ordinary mode of operating, the instrument may be used with entire convenience, in any situation; it is perfectly under the command of an individual, and is, I believe, sufficiently portable, as well as simple, for all occasions on which eudiometers are employed. The base, foot, or stand of the instrument, 1,2,3,4, fig.1, is formed from a solid block of the best well-seasoned lignum vitæ, five inches in length, four in breadth, and one inch and three-fourths in thickness. Fig. 2, represents a longitudinal * For the more perfect security and stability of the apparatus (a consideration of no little importance to those who are actively engaged in the employment of philosophical instruments), the bottom and sides of this block may be cased with wellpolished sheet copper or brass, and firmly fixed, by means of cement or small screws. One of the eudiometers in my possession is thus constructed; but when a good sound piece of lignum vitæ can be obtained, this extra measure is by no means indispensable. 164 WEEKES'S UNIVERSAL FORTABLE EUDIOMETER. and perpendicular section of the base, designed to bring more effectually under comprehension the grooves, or channels, which connect the cavities of the detonating and register tubes; 5 being the place of the former, and 6 the latter tube; 7 an orifice perpendicularly under the tube of detonation, enabling the operator to clean the inside of the tube, and affording access thereto on other occasions. The opening is closed airtight, in ordinary, by means of a good sound elastic cork; 8 is the place of the stop cock, seen at 9, fig. 1, by which the fluid in the tubes is regulated or drawn off; 10, fig. 1, is a strong eudiometer tube, of thick glass, a cubic inch of the cavity of which is graduated into tenths, fiftieths, and hundredths; it is of the common construction, as regards stability, and made with a circular rim, which is firmly cemented into a cavity in the stand, inmediately over the perpendicular channel 5, fig. 2; and is further secured by a strong circular brass collar, passed over the tube from the top downwards, and screwed or cemented into the block. This tube is mounted with the conducting wires 11, 12, and surmounted with a brass cap 13, from the centre of which arises the transfer tube 14, about one inch in length, having a bore of one. eighth of an inch diameter, and being provided at the top with the usual kind of receptacle for the screw of the small stop-cock 15, the other end of which is attached to the socket, or screw-piece, of - a small varnished gas bladder 16. This transfer tube is connected with the cavity of the glass below, by means of a minute channel drilled through the crown of the detonating tube. 17 is a solid glass pillar, which obtains motion horizontally, from the brass foot 18 revolving, by means of a screw, working in a receptacle, imbedded in the block or stand of the instrument. This pillar is mounted on the top by a brass cap and ball 19, through a channel in which slides freely a wire about two inches in length, carrying the two polished balls 20, 21; the former one and a quarter inches diameter, and the latter about three-fourths of an inch. 95 From our engraver not attending to the instructions sent him, fig 2, representing a section of the base of the eudiometer, has been placed in a vertical instead of a horizontal position, to correspond with fig. 1.--ED. M.M. At the opposite angle of the stand rises, to an equal height with the last mentioned, the brass pillar 22, with a globular or ball top, and furnished with two hooks opposite each other, 23, 24. This pillar, like the one of glass, at the opposite angle, screws into a brass collar, or foot-piece, fixed in the stand of the apparatus. The register tube 25, about sixteen inches in length, is of strong glass, and may be five-eighths, three-fourths of an inch, or even an inch in bore; being supported by the brass foot 26, which, with the aid of a leather, or elastic gum collar, screws air-tight into the block, or foot of the eudiometer, immediately over the channel 6, of fig. 2; which is provided with a proper screw-piece for its reception. This tube is also graduated into cubic inches, subdivided at convenience, and numbered from the bottom upwards;-the graduation is easily obtained, by weighing into the tube water or mercury, agreeably to the ordinary rules of such manipulations. At the time of effecting this graduation, a straight, blackened rod of beech wood, about the eighth of an inch in diameter, is to be inserted down the cavity of the tube, and of a length sufficient to project an inch above the top orifice. The insertion of this rod, at the time of graduating the tube, is, as will be hereafter seen, necessary, in order to obtain the amount of space occupied by its bulk, which is important in correctly ascertaining the degree of enlargement in the gaseous volume, during its explosion by the electric agency, when the presence of the rod in the register tube is requisite. The top of the register tube is sur mounted by a turned capital of brass, which occasionally receives a small glass funnel, through the medium of which the instrument is charged with fluid, when required for chemical operations. Fig. 3 represents an additional stopcock 27, mounted with a small gas bladder, and provided with a connecting piece 28, which is designed to screw, occasionally, upon the upper end of the stop-cock 15, fig. 1; the gas bladder 16 being removed for such purpose. By this provisional arrangement, any residual gas, from the detonating tube 10, may be transferred to the bladder 29, for the purpose of further testing or analysis; which may now be managed, by passing WEEKES'S UNIVERSAL PORTABLE EUDiometer. the residual gas into one or more test tubes, over water, first connecting a small curved jet, having a fine orifice, to the screw of the stop-cock, with which the last-mentioned bladder is furnished. Preparation of the Eudiometer for Use, and Mode of Operation. When an unknown combustible gas, or gaseous mixture, is to be examined by this instrument, it is first combined in the required proportion, with pure oxygen, and transferred to the small varnished bladder 16; but before the stopcock 15 is screwed to the top of the tube 14, the cavity of the eudiometer is to be charged with fluid. The stop-cock 9 being shut, and a small glass funnel inserted at the orifice of the register tube 30, the operator is to commence cautiously pouring in fluid, until it rises to the top of the detonating tube 10, to which it will ascend agreeably to the known laws of hydrostatics, and, as it rises, expel the air from the detonating tube before it, through the channel of the metallic transfer pipe 14.* bladder 16 is now to be placed in its proper situation, and a communication effected between it and the detonating tube, by opening the stop-cock 15. The operator should now make gentle pressure on the bladder, with one hand, while with the finger and thumb of the other hand he grasps the handle of the plug which regulates the discharge of gas through the stop-cock 15. The eye of the operator being next directed to the figured divisions of the detonating tube, and gentle pressure on the gas bladder continued, he will readily perceive when the required volume has entered, and then instantly suspend the communication, by closing the passage of the stop The *When the bladder 16 contains a considerable volume of explosive gaseous mixture-for example, oxygen and hydrogen, in the proportion in which they are employed for the gas blow pipe-and the operator wishes to avoid the trouble, or inconvenience of removing the gas bladder, all risk of explosion may be completely guarded against, by charging the cavity of the tube 14 with a few layers or strata of common sponge, but which should not be pressed over tight, lest they impede the transit of the gas from the bladder reservoir to the tube of detonation. The only chance of such an event as an explosion of the gas reservoir obtaining, perhaps, would be from the passage through the stop-cock of the bladder 16 not being perfectly air tight. This principle (the adoption of a sponge medium) I have elsewhere shown, in "An Essay on the Combustion of the Mixed Gases, &c." affords absolute security from explosion and its contingent consequences. * 165 cock; or he may charge the tube of detonation with any volume of the gas, ad libitum, and then regulate the quantity to be detonated, by keeping the finger and thumb upon the plug of the stopcock, until the pressure of the column of fluid in the register tube has returned to the bladder, by its ascent in the tube 10, all but the required volume of gaseous mixture. A slight degree of attention to the management of the stop-cock will, on a single trial, show with what facility and exactitude this operation may be accomplished. It is not advisable to operate upon large volumes; from three to five-tenths, according to the explosive force of the mixture, is as much as the instrument has capacity or is intended in general to measure, as regards enlargement of volume, and this quantity is for every useful purpose, I believe, as advantageous as ten times that amount of volume would be. The required volume of gas being admitted, the ball 21 is made to approach the ring of the conducting wire 12, by turning the pillar 17; the large ball 20 will now be brought into a convenient position for receiving the electric spark. The apparatus being in this state of preparation, the blackened rod of beech, box, ebony, or other hard wood, after it has been passed through a cork at its upper end, is to be inserted, by means of the cork, into the hollow part of the brass capital, with which the register tube 25 is surmounted, and the rod pushed through the cork until the end of the former reaches the bottom of the tube.* Two or three fine grooves cut longitudinally, on the circumference of the cork, are requisite to the egress and ingress of atmospheric air to the cavity above the fluid of the register tube, during the operative process with the eudiometer. Now let the operator open the stop-cock 9, and discharge the water from the register tube, until the surface thereof is seen on an exact level with the surface of the water in the tube of detonation; for by the introduction of the volume of gas their equilibrium will have been destroyed. During this operation of letting off water from the register tube, the column of fluid in that of detonation, will not be in the slightest degree *This rod has been previously described. 166 WEEKES'S UNIVERSAL PORTABLE EUDIOMETER. affected. One end of the brass chain seen in fig. 1, is now to be hooked to the ring of the conducting wire 11, and the other end to the hook 24, of the brass pillar 22. A second portion of chain 23, may be continued at the pleasure of the operator to the table or ground, which, under particular circumstances, may be found desirable. A small electrical machine having been previously brought into good condition, the operator is to place the eudiometer on the table, so that the ball 20 may be within a short distance of the conductor of the machine, or he may with equal convenience grasp the instrument firmly by the base or stand with one hand, while he turns the cylinder of the machine with the other. The ball 20, on receiving a large spark from the charged conductor, transmits it along the wire to the ball 21, and both being insulated by the glass pillar 17, the electricity is directed in a dense spark, by the conducting wire 12, in contact with the ball 21, through the gaseous mixture in the tube of detonation, and finds a ready course to the ground by the chain 11, 24, &c. The double motion of the balls 20, 21, by the sliding of the wire 19, and the turning of the glass pillar 17, enables the operator to regulate the strength of the spark with the utmost facility. The operative chemist needs not to be told that the combustible gaseous mixtures at the moment they are made to combine by the transit of the electric spark, obtain very considerable enlargement of volume, which we may distinguish, by calling it their explosive force. This degree of explosive force in respective mixtures, perhaps it would be advisible always to ascertain with precision, and we may presume it is an advantage to be enabled to acquire this information at the same time, and by means of the same instrument, through the medium of which the first analysis is sought. At the instant the electric spark passes between the knobs of the conducting wires 11, 12, within the tube 10, the water is seen to 1etract therein, and ascend in the tube 25, to a height corresponding with the enlargement which the gas obtains in volume, at the instant of decomposition. This effect is of a momentary nature, and the fluid in the instrument having acted as a valve and precluded the escape of gas, returns up the tube of detonation, until it reaches the line of graduation which marks the diminution or volume of gas that has disappeared. On now turning the eye to the register tube, a wet line of demarkation will be seen, upon the blackened surface of the rod before described, denoting the exact height to which the fluid has been forced to ascend, during the operation; and a moment's calculation (both tubes being graduated to show their cubic capacity)-in which we are to regard the original volume of gas introduced for detonation, will give us the amount of explosive force, or the number of times the volume of gas has enlarged at the moment of its chemical union. On the removal of the gas bladder 16, and the substitution of the bladder 29, fig. 3, with its stop-cock 27, and connecting piece 28, the residual gas may be transferred thereto, by pouring fluid by the glass funnel into the register tube, until the whole of the gas has been driven through the tube 14 into the bladder; and if the operator deems the residual volume too small, the operation may be repeated any number of times, until a sufficiency be obtained to answer the purposes of further inquiry. To enable the operator to let out, and entirely discharge at pleasure, the residual gas, from the eudiometer tube, after detonation, should he not wish to preserve it, and to repeat the experiment any number of times, without removing the bladder 16, a small screw 31 having a stout milled edge, is provided for such purpose, just below the collar of the tube 14, and by a turn or two of this screw, egress is readily given to the residual gas, the passage of the stop cock 15 being kept shut during this operation. . Application of the Apparatus to the Analysis of Cases, requiring to be operated upon over Mercury. The analysis or examination of gaseous bodies, which are wholly or in part absorbable, or otherwise deteriorated by their contact with water, and for which the philosophical inquirer finds it requisite to substitute a pneumatic apparatus charged with mercury, instead of the former fluid, are found not unfrequently to constitute an interesting feature of his researches. |