10.—SOLDERING.
If the tubes which you propose to solder are of a small diameter, pretty equal in size, and have thick sides, it is sufficient, before joining them together, to widen them equally at their extremities, by agitating a metallic rod within them. ([Pl. 1], fig. 17.)
But if they have thin sides, or are of a large diameter, the bringing of their sides into juxta-position is very difficult, and the method of soldering just indicated becomes insufficient. In this case you are obliged to seal, and subsequently to pierce, the two ends which you desire to join. The disposition which this operation gives to their sides very much facilitates the soldering.
Finally, when the tubes are of a very different diameter, you must draw out the extremity of the larger and cut it where the part drawn out corresponds in diameter to the tube which it is to be joined to. [Pl. 1], fig. 9 and 15, exhibit examples of this mode of adapting tubes to one another.
For lateral solderings you must dispose the tubes in such a manner that the sides of the orifices which you desire to join together coincide with each other completely. See [pl. 1], fig. 7.
When the holes are well prepared, you heat at the same time the two parts that are to be soldered together, and join them at the moment when they enter into fusion. You must push them slightly together, and continue to heat successively all their points of contact; whereupon the two tubes soon unite perfectly. As it is almost always necessary, when you desire the soldering to be neatly done, or the joint to be imperceptible, to terminate the operation by blowing, it is proper to prepare the extreme ends of the tubes before-hand. That end of the tube by which you intend to blow should be carefully drawn out, provided it be so large as to render drawing out necessary; and the other end of the tube, if large, should be closed with wax, as in [pl. 1], fig. 9, or if small, should be sealed at the lamp ([pl. 1], fig. 15). When the points of junction are perfectly softened, and completely incorporated with each other, you introduce a little air into the tube, which produces a swelling at the joint. As soon as this has taken place, you must gently pull the two ends of the joined tube in different directions, by which means the swelled portion at the joint is brought down to the size of the other parts of the tube, so that the whole surface becomes continuous. The soldering is then finished.
To solder a bulb or a cylinder between two points, to the extremity of a capillary tube, you cut and seal one of the points at a short distance from the bulb ([pl. 1], fig. 16), and at the moment when this extremity is in fusion you pierce it by blowing strongly at the other extremity. By this means the opening of the reservoir is terminated by edges very much widened, which facilitates considerably its being brought into juxta-position with the little tube. In order that the ends of the two tubes may be well incorporated the one with the other, you should keep the soldered joint for some time in the flame, and ought to blow in the tube, push the ends together and draw them asunder, until the protuberance is no longer perceptible.
If, after having joined two tubes, it should be found that there still exists an opening too considerable to be closed by simply pushing the two tubes upon one another, you can close such an opening by means of a morsel of glass, applied by presenting the fused end of an auxiliary tube.
You should avoid soldering together two different species of glass—for example, a tube of ordinary glass with a tube of flint-glass; because these two species of glass experience a different degree of contraction upon cooling, and, if joined together while in a fused state, are so violently pulled from one another as they become cool, that the cohesion of the point of soldering is infallibly overcome, and the tube breaks. You ought also, for a similar reason, to take care not to accumulate a greater mass of glass in one place than in another.
If the first operation has not been sufficient to complete the soldering, the tube must be again presented to the flame, and again pushed together at the joint, or drawn asunder, or blown into, according as it may appear to be necessary. In all cases the soldering is not truly solid, but inasmuch as the two masses of glass are well incorporated together, and present a surface continuous in all points.
The mineralogical flame ([pl. 1], fig. 1, A´ B) is that which is to be employed in preference to the larger flame, when you desire to effect a good joining: it is sufficient to proportion the size of the flame to the object you wish to execute.
THE
ART OF GLASS-BLOWING.
IV.—Construction of Chemical and Philosophical Instruments.
When a person is well acquainted with the fundamental operations which we have just described, the preparation of the instruments of which we are about to speak can present scarcely any difficulty. Indeed, some of them are so extremely simple, and are so easy of execution, that it is sufficient to cast a glance upon the figures which represent them, to seize at once the method which must be followed in their construction. Of such instruments we shall not stop to give a detailed description, but shall content ourselves with presenting the design.
On the other hand, it is of importance to observe that a certain number of instruments are graduated or furnished with pieces, or mountings, of which it is not the object of our art to teach the construction, and which demand a more or less extensive knowledge of the sciences. We shall treat of these mountings but summarily, referring the student, for more detailed instructions, to the works on natural philosophy and chemistry, in which these instruments are especially treated of. Our reason for this is, that we do not wish to abandon the plan we had adopted of describing simply the art of glass-blowing. To describe the use and application of philosophical instruments, or to explain the principles on which they act, would be passing quite out of our province.
Adapters.—These are tubes of glass of various forms, employed in chemistry to connect together the different pieces constituting an apparatus—as, for example, to join a retort to a receiver during the operation of distillation. You should take care to border the extremities of an adapter; or you may widen them into the form of the mouth of a bottle, when they are to be closed air-tight by corks. Besides this, there is nothing particular to be observed in the preparation of adapters.
Apparatus for Boiling in Vacuo.—Represented by [pl. 3], fig. 19. Employ a tube about a quarter of an inch in diameter. Blow two bulbs; give the tube the necessary curvature; fill one of the bulbs with nitric ether; boil the ether to expel the atmospheric air from the apparatus, then seal the opening in the other bulb.
Apparatus for Freezing in Vacuo. The Cryophorus.—Take a tube one-third of an inch or rather more in diameter, and pretty thick in the sides. Blow a bulb at each end; the first at the sealed part of the tube, the other at the open point; then give to the tube the curvature represented by [pl. 3], fig. 32. Introduce as much water as will half fill one of the bulbs; make the water boil, and draw off the point and seal the apparatus during the ebullition.
Apparatus for conducting Water in bent Tubes.—Solder a funnel (see Funnels) to the end of a tube; pierce two holes in this tube in the same line, and solder to each a little addition proper to receive a cork. Finish the instrument by bending it in the manner indicated by [pl. 4], fig. 18.
Apparatus for Experiments on Running Liquids.—A tube bent once at a right angle, mounted with a funnel, pierced laterally, and soldered at the same point to a smaller tube. See [pl. 3], fig. 17.
Apparatus for Exhibiting the Phenomena of Capillary Tubes.—This apparatus consists of a capillary tube soldered to another tube of a more considerable diameter. Sometimes it is bent like the letter U. [Pl. 3], fig. 15.
Apparatus for the Preparation of Phosphuret of Lime.—An apparatus that can be employed for the preparation of phosphuret of lime, as well as in a variety of other chemical experiments, consists of a tube sealed at one extremity, slightly bent and choked at two inches and a half from the sealed part, and drawn out (after the introduction of the substances to be operated upon) at the other extremity. This little distillatory apparatus is represented by [pl. 3], fig. 29.
Archimedes’s Screw.—There is no particular process for the making of this instrument. It is, however, necessary for one who would succeed in making it, to exercise himself in the art of well bending a tube. After a few attempts, you may finish by producing a pretty-regular spiral. The tube chosen for this instrument should be six or seven feet long, and about one-third of an inch in diameter. You commence by making a bend, nearly at a right angle, about four inches from one of its extremities. This bent portion serves afterwards as a handle, and very much facilitates the operation; it represents the prolongation of the rational axis which may be conceived to pass through the centre of the spiral. See [pl. 4], fig. 10.
Barker’s Mill.—Apparatus for exhibiting the rotatory motion produced by the running of liquids.—Contract a tube at its two extremities, pierce it laterally about the middle of its length, and solder to the hole an additional tube, terminated by a funnel. Soften the principal tube at the side opposite to the part that was pierced, and form there a conical cavity by pressing the softened glass inward with the aid of a metallic rod. This cavity must be so carefully made that the whole apparatus can be supported on a pivot. Bend the contracted ends of the tube horizontally, and in different directions, cut off their extremities at a proper length, and slightly border the edges of the orifices. See [pl. 3], fig. 33.
You may produce this apparatus under a different form, as may be seen at [pl. 3], fig. 5.
Barometers.—Barometers serve to measure the pressure of the atmosphere. The following are the varieties most in use.
Cistern Barometer.—Take a tube about thirty-two inches long, and at least one-third of an inch in diameter, internally; seal one of its extremities, free it with most particular care from moisture, fill it with mercury, and make the mercury boil in the tube, by heat, in order to drive out every particle of air which might be present. When the tube is full of mercury, and the boiling has taken place, turn it upside down, and plunge the open end into a cistern also filled with mercury which has been boiled. See [pl. 2], fig. 4.
Dial (or Wheel) Barometer.—The tube intended for this barometer should be very regular in the bore. It should be thirty-nine inches long. Close it at one end, and bend it like the letter U at about thirty-two inches from the sealed extremity. See [pl. 2], fig. 5, and Graduation of the Dial Barometer.
Syphon Barometer.—Make use of such a tube as might be employed for a Cistern Barometer; solder to its open end a cylindrical or spherical reservoir, and bend the tube close to the point of junction in such a manner as to bring the cylinder parallel with the tube. If the reservoir is to be closed with a cover of leather, cut off the remaining point of the cylinder, slightly widen the orifice, and then border it. If no leather is to be applied, but the point of the cylinder left open, it is necessary, after the introduction of the mercury, to draw off the point abruptly, and to leave an opening so small that mercury cannot pass by it. [Pl. 2], fig. 6.
Stop-Cock Barometer.—This differs from the preceding barometer only by having a stop-cock mounted in iron between the reservoir and the tube.
Compound Barometers.—Blow a bulb at each end of a barometer tube of about thirty-three inches in length. Solder a small and almost capillary tube to the point which terminates one of the bulbs, and bend the great tube very near this bulb. This must be done in such a manner that the centre of one bulb shall be thirty inches from the centre of the other bulb. Introduce a quantity of mercury sufficient to fill the great tube and half the two bulbs; fill the remaining space in the last bulb with alcohol.
You may give a different disposition to this instrument. Divide a barometer tube into two, three, or four pieces, and reunite the pieces by intermediate capillary tubes, so as to form a series of large and small tubes, soldered alternately the one at the end of the other. Then communicate to this compound tube the form exhibited by [pl. 3], fig. 25, and join, at each superior bend, a little tube, for the convenience of easily filling the instrument with mercury: seal these tubes as soon as the mercury is introduced. The graduation of compound barometers is made by bringing them into comparison with a good standard barometer. After taking two or three fixed points, it is easy to continue the scale.
Gay Lussac’s Barometer.—Take a tube which is very regular in the bore, four-tenths of an inch in diameter, and thirty-five inches and a half in length. Seal one of its extremities and draw out the other; then cut the tube at about two-thirds of its whole length from the sealed end, and reunite the two pieces by means of a capillary tube soldered between them, the whole being kept in a line. See [pl. 2], fig. 1. Pierce laterally the part of the tube which is drawn out, at some inches from the base of the point, and force the margin of the hole into the interior of the tube, by means of a conical point of metal, in such a manner as to form a little sunk funnel, of which the orifice must be very small. After having introduced the proper quantity of mercury into the instrument, boil it, and assist the disengagement of the bubbles of air by agitating a fine iron wire within the tube. Then remove the part of the tube which was drawn out, by sealing the end of the wide part. Give to the whole instrument the curvature indicated by [pl. 2], fig. 3.
Bunten’s Barometer.—This instrument differs from the preceding but in one point, namely, that the capillary tube is formed of two soldered pieces, of which the one, passing into the other, is terminated by a capillary point. This arrangement is exhibited by [pl. 2], fig. 2.
Barometer pierced laterally for Demonstrations.—Take a tube thirty-nine inches long, with thick sides, and two-tenths of an inch internal diameter. Seal it at one end, and choke it at the distance of eight inches therefrom. Pierce a hole in the tube about twelve or sixteen inches from the choked part, and solder to the hole an additional piece, which can be closed by a cork or covered by a piece of bladder. The instrument is represented by [pl. 2], fig. 15.
Bell-Glasses for Experiments.—These are pieces of tube sealed at one end, and widened or bordered at the other. They are extremely useful, and much employed in chemical experiments. They also supply the place of bottles for preserving small quantities of substances. Sometimes they are required to be straight, as [pl. 3], fig. 12. Sometimes they need to be curved, as [pl. 3], fig. 29. This is particularly the case when they are to be employed as retorts, for which purpose the sealed part should be made thin. [Pl. 3], fig. 6, exhibits a retort with a tubulure.
Blowpipe.—We shall give in this article an account of the various pieces of glass which form part of the blowpipe described in the early part of this work. See [pl. 1], fig. 19.
The beak C, which is employed with the candlestick, is merely a bent tube, at the extremity of which a bulb is blown. The bulb is terminated by a point, the thickness of the sides of which is augmented by turning it for a long time in the flame.
As for the beak used with the lamp, it is simply a bent tube C´, of which the orifice has been diminished by turning it round in the flame. The point of this beak is not drawn out like that of the beak described in the preceding paragraph, but is allowed to be thick, that it may not melt in the flame of the lamp.
The tube D F has four-tenths of an inch internal diameter, and is pretty thick in the sides. You must commence by bordering and slightly widening one of its extremities, and then proceed to choke it at about two inches from its other extremity, taking care to give to the choked part a figure as perfectly conical as possible, in order that the valve may act well. We have described the valve at length at p. 6.
The tube d is as much narrower than the tube D F as is necessary to permit it to pass up and down within the latter. Its use is to lengthen or shorten the tube for the convenience of the blower. The lower end is wound round with waxed thread, to make it fit air-tight. The mouth-piece is executed by widening the end of the tube, and then, while the widened part is still soft, by pressing the two sides obliquely, one against the other. By this means you give to the mouth-piece a flattened form, which adapts it better to the lips. The tube is finished by slightly bending this extremity.
In order that the bladder, or air reservoir, may be conveniently and securely attached to the tube E, you must take care to widen the end of this tube, and to turn up the edges strongly, by pressing the soft end against a flat metallic surface.
Capsules.—These are very small mercury funnels, of which the opening or neck has been closed. To transform these funnels into capsules, you must cut the neck as close as possible, and then soften, close, and flatten the opening. In performing this operation, hold the capsule by the edge with your pincers, and employ a piece of metal to press the glass together and make it close the hole and form the flat bottom of the capsule. See [pl. 2], fig. 23.
Another Method.—After having blown a bulb at the end of a point, soften a narrow zone of the bulb, and then blow suddenly and strongly into it; by which means you separate the bulb into two capsules, which only need to be bordered. If you find any difficulty in presenting to the flame the capsule which forms the part of the bulb opposed to the point, you can attach to it a little rod of glass, which you can afterwards easily separate by a slight smart blow.
Occasionally you will have to make capsules with double sides, which will be described at the article Nicholson’s Hydrometer.
Cartesian Devils.—Blow a bulb at the extremity of a very small tube, and heat a portion of the bulb, for the purpose of prolonging it into a beak. This can be effected with the aid of an auxiliary tube, which, on being joined to the heated part of the bulb, carries away with it the portion of glass which adheres. This portion of the bulb becomes thus prolonged into a little point, which must be cut at its extremity, so as to leave a small opening. The principal tube must be cut at the distance of half an inch from the bulb, and the ends of it must be drawn out and twisted into a ring. Instead of forming laterally a little beak to the bulb, you may pierce the tail, after twisting it into the form of a ring, or you may manage in such a manner as not to obliterate the canal of the twisted part. In general, little enamel figures are suspended to the ring of these globes, as is represented by [pl. 2], fig. 22. A simple bulb, blown at the extremity of a small portion of tube, can supply the place of the Ludion or Cartesian devil. See [pl. 2], fig. 8.
Communicating Vases.—Employ a tube of a large diameter; terminate one of its extremities with a funnel, fashion the other like the neck of a bottle; and bend the tube into the shape shewn by [pl. 4], fig. 11. Then twist some other tubes into various forms, according to the end you propose to attain, and adjust these tubes to the neck of the large tube by means of corks, which have holes bored through them. In this manner an exchange of tubes is provided for various experiments.
Dropping Tubes.—The name dropping tube is given to an instrument of glass which is very much employed in chemistry, for the purpose of transferring small quantities of liquor from one vessel into another, without disturbing either of the vessels. Dropping tubes are made of a great variety of forms and sizes, according to the purposes to which they are intended to be applied.
Blow a bulb between two points, and then, before the glass has regained its consistence, lengthen the bulb into an oval form. Cut and border the two points.
If the bulb, or reservoir, is to be so large that it cannot be formed at the expense of the thickness of the tube, and yet be sufficiently strong, it must be blown separately from a larger tube, and then soldered to two smaller tubes, one of which should have a certain curvature given to it. See [pl. 2], fig. 20.
Sometimes a dropping tube is employed to measure small quantities of liquid. In this case the point should be drawn off abruptly, and the scale should be marked on the shank or tube with spots of black enamel.
[Pl. 2], fig. 21, represents a peculiar variety of dropping tube employed in some experiments. It is made in the same manner as the common dropping tubes, excepting that, when the tail is formed, it is sealed at the extremity, bent there into a ring, and then pierced at A.
[Pl. 3], fig. 26, represents another variety of dropping tube, a description of which is unnecessary.
Fountains.—It will readily be understood by those acquainted with the construction of hydraulic apparatus, that, by means of a judicious arrangement of glass tubes, a great variety of fountains may be produced. The following are given as examples.
Fountain of Circulation.—Take a tube, twenty-four or thirty inches long, nearly half an inch in diameter, and with pretty thick sides; blow a bulb at one of its extremities, and bend the other into a U, after having drawn it out as indicated by [pl. 3], fig. 4. Pierce the tube at B, and join there a short piece adapted to receive a cork. Then prepare a bulb of the same size as the first bulb, and solder it to the extremity of a very long and almost capillary tube, which you must bend in zig-zag, in such a manner as to make it represent a Maltese cross, a star, a rose, or any other figure that may be suggested. The side of the bulb opposite to that which is attached to this twisted tube, ought to be formed like the neck of a bottle, in order that it may receive the drawn-out part of the larger tube, which should enter the bulb until the point of the large tube nearly touches the neck of the little tube at its junction with the bulb. This disposition is shewn in the figure. Seal now the other end of the little tube to the bulb of the large tube; then, with a little cement or sealing-wax, close the space between the bulb of the little tube and the point of the large tube. The instrument being thus prepared, as much alcohol, previously coloured red, must be inserted by the neck b as is sufficient to fill one of the bulbs. The neck is then closed with a cork, and a little cement or sealing-wax. Or, instead of forming this neck to the instrument, the additional piece may be drawn out to a point, which permits it to be sealed hermetically.
Fountain of Compression.—Introduce into a tube of large diameter a piece of capillary tube with thick sides. This must pass a little beyond the extremity of the large tube, which is to be softened and soldered to the other, so that it shall be fixed concentrically. The common point is then to be drawn out. When the tube is quite cold, and the small tube properly fixed in the centre of the large one, cut the latter at a proper distance, border it, and choke it near the end, which must be fashioned in such a manner as to be capable of being completely closed by a cork. See [pl. 2], fig. 29.
Intermitting Fountain.—This apparatus is represented by [pl. 3], fig. 16. Solder a cylindrical reservoir to the extremity of a capillary tube, pierced at a, and sealed at its extremity. Draw out abruptly the point of the reservoir, and give it a very small orifice; then give to the capillary tube the form indicated by the figure. Prepare next a funnel resembling a mercury-funnel, but much larger; choke the neck of this funnel, and bend the tube into the form of a syphon.
Hero’s Fountain.—Solder a bulb to the extremity of a tube, and transform the bulb into a funnel. Close the funnel with a cork, and solder to the other end of the tube a bulb similar to the first. Next, solder a third bulb between two tubes, of which one must be twice as long the other; solder the longer of these tubes to the bulb of the first tube, and draw out the point of the shorter tube. You have now a long tube, with a funnel at one end, a contracted point at the other, and two bulbs in its length. Give to the whole apparatus the form indicated by [pl. 3], fig. 21.
Funnels.—It will be seen, upon looking over the engravings, that funnels require to be made for a great variety of instruments; you ought therefore to acquire as soon as possible the art of making them well. The following are those most frequently required.
Retort Funnel.—Blow a bulb at the extremity of a tube; present the superior hemisphere of the bulb to the flame, and when it is sufficiently softened, blow strongly into the other end of the tube. The air will force its way through the bulb, making a hole which will be larger or smaller according to the extent of surface which may have been softened. The opening of the funnel being made thus, there is nothing more to do than to adjust the edges, which, in the present state, are both fragile and irregular. This it is very easy to do. The edges are softened, the most prominent parts are cut off with the scissars, and the parts which are thin are bent back on themselves, that they may become thicker. Upon turning the funnel round in the flame, the smaller irregularities give way, and the edges become rounded. See [pl. 2], fig. 24.
When the funnel is desired to be very large in proportion to the size of the tube, a bulb is made from a larger tube, and afterwards soldered to the small tube, and transformed into a funnel in the manner above described.
Funnel for introducing Mercury into narrow tubes.—The mercury-funnel is represented by [pl. 2], fig. 25. Blow a bulb between two points; cut off one of the points, and open the bulb at that place, in the manner described in the preceding article.
Hydrostatic Funnel.—This is represented by [pl. 3], fig. 31. It is an instrument of constant use in chemical experiments. Form a funnel at the extremity of a tube in the manner described above, having previously blown a bulb near the middle of the tube. When this has been done, bend the tube into the form shown by the figure.
Hour-Glasses.—Blow four bulbs on a tube close to each other; open the two end bulbs like funnels, and then form them into flat supports or pedestals, according to the method described at the article Test-glass with a foot. Obstruct entirely the canal which separates one of these feet; choke to a certain extent the passage between the two remaining bulbs; and close the canal between the other foot and the bulbs, after introducing the quantity of sand which you have found to be necessary. See [pl. 3], fig. 13.
Hydraulic Ram.—This instrument is represented by [pl. 4], fig. 15. Employ a tube about six feet long, with thick sides and of large diameter. Seal it at one extremity, k, and border it at the other; solder at p an additional piece, choked so as to receive a valve. Pierce the tube at l; draw it out, and fix a funnel there; then twist the tube into a spiral. Form, on the other hand, a fountain of compression, o, and a funnel, m; and fix both of these pieces by means of sealing-wax, as soon as the two valves p and l have been put into their places.
Hydrometers.—Hydrometers are instruments which, on being plunged into liquids, indicate immediately their density or specific gravity. Areometers differ from hydrometers sometimes in graduation, sometimes merely in name. The following are examples of hydrometers, of which a great many varieties are in use.
Baumé’s Hydrometer.—Make a cylinder between two points, and solder it to the extremity of a tube with thin sides, and which must be very regular on the outside. Close the open part which is to form the stalk of the hydrometer with a little wax. See [pl. 1], fig. 9 and 15. When the soldering, which must be well done, is complete, and the stalk well centered, choke the reservoir at a little distance from the base of the point, by drawing it out in such a manner as considerably to diminish the canal in this part. Remove then the ball of wax which closed the tube, draw off the point of the cylinder, and make the part which was pulled away from the cylinder by the choking, into a bulb, by blowing with precaution into the tube. If the reservoir is required to be spherical instead of cylindrical, it must be softened and expanded by blowing. When it is intended to ballast the instrument with mercury, the canal must be completely stopped at the point where it is choked. In this case, the part drawn away from the cylinder is expanded into a bulb by blowing through the extreme point, which is to be cut off after the instrument is completed.
In the first case, you ballast the instrument with lead shot, which you fix in the lower bulb by means of a little wax, which closes the canal at the choked part. In the second case, after having proved the ballast by putting it first into the large reservoir, it is removed into the little bulb, and the latter is immediately sealed.
One of the essential conditions of a good hydrometer is that the stalk should keep a perfectly vertical position when the instrument is plunged in water. If, therefore, on proving the ballast, you perceive the stalk to rest obliquely, you must take care, on retiring it from the water, to wipe it dry, and to present the choked part between the cylinder and the little bulb to the flame; when it is softened, it is easy, by giving it a slight bend in the direction where the stalk of the hydrometer passes from the vertical, to rectify the defect.
Finally, when the instrument is ballasted, you must seal the stalk, after having fixed in its interior the strip of paper which bears the graduated division.
This method of operation serves equally for all the areometers known under the names of areometer of Baumé, pèse-sels, pèse-liqueurs, pèse-acides, and hydrometers, which differ only in the scheme of their graduation. As to the size and the length of the stalks, they depend upon the dimensions you desire to give to the degrees of the scale, and upon the use to which the instruments are destined. For the areometer of Baumé, and for the pèse-sels, the stalks are generally thicker and shorter than for hydrometers. [Pl. 4], fig. 19, 20, and 21, represent different hydrometers.
Nicholson’s Hydrometer.—Solder a bulb to the extremity of a capillary tube; open it so as to form a very wide funnel, or rather capsule; border the edges, and melt the point of junction with the tube so as to close the opening of the latter. Solder the other extremity of the tube to a cylindrical reservoir. Soften the point at the lower extremity of the cylinder, and obstruct the canal so as to convert the point into a glass rod; bend this rod into a hook. Now blow a bulb at the end of a point, as if to make a mercury funnel; but, after having softened the hemisphere of the bulb opposite to the point, and placed the latter in the mouth, instead of blowing into the bulb so as to make a funnel, strongly suck air from the bulb: by this means the softened part of the glass is drawn inwards, and you obtain a capsule with double sides, as exhibited by [pl. 2], fig. 17. This capsule must have a small handle fastened across it, by which it may be hung to the hook formed at the bottom of the cylinder described above.
This hydrometer being always brought to the same level, the point to which it must be sunk in the liquid experimented with, is marked on the stalk by applying a little spot of black enamel. The instrument is represented by [pl. 4], fig. 23. A variation in form is shewn by [pl. 4], fig. 22.
Hydrometer with two Branches.—To measure the relative density of two liquids which have no action on each other, you employ a simple tube, bent in the middle and widened at its two extremities. See [pl. 2], fig. 11.
Hydrometer with three Branches.—This consists of a tube bent in such a manner that the two branches become parallel. To this tube another is soldered at the point of curvature, and is bent in the direction exhibited by [pl. 2], fig. 12. When the two branches are put into different liquids, and the operator sucks air from the third branch, the two liquids rise in their respective tubes to heights which are in the inverse ratio of their specific gravities.
Hydrometer with four Branches.—This is merely a tube bent three times, and widened at its extremities. [Pl. 2], fig. 13.
To graduate hydrometers with two, three, and four branches, you have to divide their tubes into a certain number of equal parts.
Manometers.—Make choice of a tube nearly capillary, very regular in the bore, and with sides more or less thick, according to the degree of pressure which it is to support. Seal this tube at one end, blow a bulb with thick sides near the middle, and curl it in S, just as is represented by [pl. 2], fig. 9. For manometers which serve to measure the elasticity of the air under the receiver of the air-pump, what is generally employed is a tube closed at one end and bent into a U. [Pl. 2], fig. 10. You should take care to contract these at some distance from the sealed part, in order to avoid the breaking of the instrument on the sudden admission of air. Manometers are graduated, as will be explained in the sequel.
Mariotte’s Tube.—This is represented by [pl. 2], fig. 7. It consists of a tube thirty-nine inches long, closed at one end, bordered and widened at the other, and bent into a U at the distance of eight inches from its sealed end. The graduation of this instrument will be described hereafter.
Phosphoric Fire-Bottle.—This is a short piece of tube closed at one end, and widened and bordered at the other, in such a manner as to receive a cork. [Pl. 3], fig. 34. It is in this little vessel that the phosphorus is enclosed. Glasses of this form can be employed in a great variety of chemical experiments.
Pulsometer.—This instrument consists of a tube, of which each extremity is terminated by a bulb; it is partly filled with nitric ether, and sealed at the moment when the ebullition of the ether has chased the atmospheric air wholly from the interior of the vessel. [Pl. 2], fig. 16.
Pump.—Solder a cylinder, B ([pl. 4], fig. 12), to the extremity of a small tube, C, and form their point of coincidence into a funnel, to which you will adapt a valve. Pierce the wide tube or body of the pump at D, and solder there a piece of tube bent into an elbow and widened at the other end into a funnel, which is to be furnished with a second valve, as is represented in the figure. Prepare then the fountain of compression E, and, by means of a cork and a little sealing-wax, fix it upon the branch D. To prepare the piston, A, blow a bulb at the end of a tube, flatten the end of the bulb, and choke it across the middle, in order to form a place round which tow can be twisted, to make it fit the tube air-tight. Finish the piston by twisting the other end of the tube into a ring, as at A. The valves are formed of small cones of cork, or wood, having in the centre an iron wire of sufficient size and weight to enable them to play well.
Retort for Chemical Experiments.—Plate 3, fig. 9, represents a combination of a large and a small tube, forming a retort, which can be employed with much advantage in many chemical experiments. When a gas is to be distilled by means of such a vessel, the ingredients are put into the wide tube, which is previously closed at one end, and then the other end of the tube is either drawn out or soldered to a narrow tube. [Pl. 3], fig. 8 and 29, represent such vessels under different forms. Very often a sort of retort can be formed by joining a wide tube to a long bent narrow tube, by means of a cork.
Tubulated Retort.—This is represented by [pl. 3], fig. 6. Prepare a retort, such as is described in the preceding article, but one which is bent near the closed end; pierce it at A (fig. 6), and solder there a little piece of tube previously drawn out and sealed, such as is represented by [pl. 1], fig. 11. When the soldering is finished, soften the end of the little tube, pierce it, and fashion it into a bottle neck, so that it can be closed by a cork. Finish the instrument by forming the open end according to the purpose to which it may be destined. In the figure, the end is represented as drawn out for the convenience of blowing into the retort to pierce the tubulure.
Rumford’s Thermoscope.—This instrument is represented by [pl. 3], fig. 35. It is necessary to take a tube almost capillary, to solder a bulb at each extremity, to pierce it laterally at b, and to solder there a piece of tube previously drawn out, but of which you open the point for the purpose of finishing the sealing of the bulb A. After doing this, you bend the two branches, as shewn in the figure. When the liquid has been introduced into the instrument, you must seal the little piece of tube which serves as a reservoir.
This instrument can be made in another manner. Take two pieces of tube, one of them twice as long as the other; solder a bulb at one end of each of these tubes, and at about the third part of the length of the long tube, parting from the bulb, bend it at a right angle; pierce the little tube at a corresponding distance, and solder to the hole the end of the long tube. The soldering being finished, and the whole system having the form indicated by [pl. 3], fig. 35, introduce, by the open end of the short tube, a small quantity of coloured acid, and then seal the end of the short tube, which serves as a reservoir.
The interior diameter of the tubes which are generally employed as thermoscopes, is one-eighth or one-twelfth of an inch. The mode of graduation is described in a subsequent chapter.
Syphons.—The simple syphon is a glass tube bent, at a little distance from the middle, into a form which is intermediate between those of ⋂ and ⋀, the legs being stretched apart like those of the latter, but the bend being rounded like that of the former. The tube is bent near the middle, and not exactly at the middle, in order that the legs may be of unequal lengths; an arrangement which is indispensable. Syphons are made of different lengths and diameters, for various purposes. They can be made of tubes so capillary that it is sufficient to put them into water to make them act: the liquid rises in them by capillary attraction, and does not require to be sucked through the tube, as it does when large syphons are employed.
Wirtemberg Syphon.—This syphon is the same as the simple syphon, excepting that the two branches are of equal length, and are bent in U at both extremities. [Pl. 3], fig. 22.
Syphon with three Branches.—This instrument is represented by [pl. 2], fig. 19. Close a tube at one end and draw it out at the other; pierce it at some inches from the contracted extremity, and solder to the hole a little tube of which the other end has been closed with wax. Give the tube the bend necessary to constitute a syphon, and open the two branches. The soldering of the two tubes is facilitated by giving to the extremity of the little tube a bend which adapts it to be applied parallel to the large tube. When the syphon is desired to be well finished, the mouth-piece of the little tube must be bordered and widened, and a bulb must be blown near the mouth-piece.
Syphon with Jet of Water.—This instrument is represented by [pl. 3], fig. 1. Take a tube of a large diameter, close it at one end, and draw it out at the other. Cut the contracted part in such a manner as to be able to introduce, through the orifice, the extremity, also drawn out, of another tube, which should be almost capillary. Solder these together in such a manner that the point of the small tube shall remain fixed about an inch within the interior of the reservoir. Pierce again the latter, at B, and solder there another branch of the same diameter as the former; but fix it in such a manner that its side shall be contiguous to the side of the reservoir. Finally, give to the branches the bend represented by the figure.
Spoons.—Solder a bulb to the extremity of a capillary tube; open the bulb as for a funnel, but make the opening laterally. Cut with scissars the edges of the part blown open, and in such a manner as to form a spoon or a ladle, according as the bulb had the form of a sphere or an olive. This instrument is useful for taking small quantities of acids. [Pl. 3], fig. 11.
Spirit Level.—The spirit level is represented by [pl. 2], fig. 28. Choose a piece of tube very straight, and with sides precisely of the same thickness in all parts. Seal it at one end, and draw it out abruptly at the other. Fill it almost entirely with alcohol, and seal the point by the jet of a candle.
Test Glass with a Foot.—Take a tube drawn out at one end; choke it at an inch from the base, in such a manner as to obstruct the canal almost entirely. [Pl. 1], fig. 12. Cut off the point, close the opening, and soften the whole end completely; then blow it into a bulb and burst it into a funnel. Now present the contracted part to the fire, so as totally to close the passage. Border and soften the funnel, and by pressing it against a flat plate of metal give it the form of a foot, or pedestal. Cut the tube at the length which you desire the test-glass to have, and border the edges of the opening. This is a very useful little chemical instrument. It is represented by [pl. 3], fig. 10.
Thermometers.—Thermometers are instruments employed for appreciating changes of temperature, either in the atmosphere or in substances which we have occasion to examine. The following are the principal varieties now employed.
Ordinary Thermometer.—If you desire to make standard thermometers, you must have capillary tubes of perfect accuracy in the bore. You are assured of regularity in the diameter of a tube when a drop of mercury, made to pass along the canal by means of a gentle inclination, or by air blown from an Indian-rubber bottle, gives everywhere a metallic column of the same length.
For ordinary thermometers this precaution is superfluous. In all cases you employ a tube more or less capillary, at one of the extremities of which you blow or solder a spherical or cylindrical reservoir. See [pl. 4], fig. 1 and 2. You fill the instrument with well-purified mercury, or alcohol, which you boil in the tube, in order to chase the air from it. As it is necessary to heat the instrument throughout its whole length, you must place it on a railing of iron wire, inclined in the manner represented by [pl. 4], fig. 14, and covered with burning charcoal, or red-hot wood ashes. It is better, however, to employ a kind of muff, formed of two concentric wire grates, between which you put burning charcoal, and reserve the centre for the instrument. The tube is thus kept in a vertical position, which allows the bubbles of air to escape with more facility. An iron wire is made use of to fasten the tube precisely in the centre of the column of fire. The operation is considerably promoted by soldering a little funnel to the upper extremity of the thermometer tube; and, in order to avoid the interruption of the column of liquid by bubbles of air, it is better to give to the superior part of the reservoir the form of a cone ([pl. 4], fig. 3), rather than to preserve the completely spherical form indicated by [pl. 4], fig. 2.
When the ebullition has expelled all the air which was contained in the mercury, or alcohol, you immediately plunge the open extremity of the instrument into a vessel filled with one or the other of these liquids; or, instead of this, you pour the liquid into the funnel, in order that the instrument may be quite filled at the common temperature. You then cut off the funnel, if one has been used, and, by properly elevating the temperature of the reservoir, you expel so much of the liquid that the summit of the column rests at the point which you desire to make choice of for the mean temperature: this operation is termed regulating the course of the thermometer.
There are two methods of closing thermometers: you may either produce a vacuum above the column of mercury, or you may allow air to remain there. In the first case, after having drawn out the end of the tube, you heat the liquid until a single drop passes out of the opening; you then instantly bring the point into the jet, and seal it.
In the second case, you seal the instrument at the ordinary temperature, and having previously raised to a reddish-white heat the button of glass which is formed by the sealing, you suddenly elevate the temperature of the mercury. The liquid, on rising, compresses the enclosed air, which dilates the red-hot button at the summit of the tube, and produces a species of reservoir. This reservoir is indispensably necessary when you leave air above the column of liquid, in order to provide against the bursting of the instrument on those occasions when the temperature of the mercury comes to be considerably elevated. See [pl. 4], fig. 13.
Dial Thermometer.—Terminate a piece of tube, of six-tenths of an inch in diameter, with two points, and solder to one of these points a tube one-eighth of an inch in diameter and six inches long; close the end of this small tube, and, heating a zone of the reservoir, near the base of the other point, blow a bulb there. Cut off the point by which you have blown, at a little distance from the bulb; open and border the end of the narrow tube, and bend it into a U. See [pl. 4], fig. 16.
Fill the bulb and the reservoir with alcohol, and add a drop of mercury which fills a certain space in the narrow tube. This mercury bears on its surface a little iron weight, to which a thread is fastened; the other end of this thread passes over a pulley, whose axis turns a needle. The expansion or contraction of the alcohol causes the mercury to rise and fall, and consequently produces a movement of the needle or index of the dial. This thermometer is graduated like the others, by being brought into comparison with a standard thermometer.
Chemical Thermometer.—This instrument is merely a common thermometer, the divisions of which, graduated on paper, are enclosed in a very thin glass tube, to hinder them from being altered or destroyed when the instrument is plunged into liquids. [Pl. 4], fig. 4, 5, 6, and 7, represent chemical thermometers of various kinds.
The case of the thermometer can be made in two different ways. According to the first, you take a tube of a pretty large diameter, and with very thin sides; you draw out one end and obliterate the point, which you bend into a ring, in a direction perpendicular to that of the case; you pass through this ring the stalk of the thermometer, which is thus placed parallel to the large tube. After having fixed the graduated scale in the interior of the case, by means of a small drop of sealing-wax, which has been dropped on the slip of paper, and which, being supported against the side of the case, needs only to be warmed to adhere there and fix the scale securely to its envelope, you close the upper extremity of the case by drawing it out, obliterating the canal and soldering it to the thermometer tube which has been introduced into the ring at the lower end of the case. You heat the connecting piece till it is soft, and then push the thermometer up and down until the zero marked on its tube corresponds with the zero marked on the scale within the case. See [pl. 4], fig. 6 and 7.
The second method of making the case is as follows:—You take a tube with thin sides, and sufficiently large to contain the entire thermometer; you draw out the tube at one end, and choke it at some distance from the point of the contracted part. This you must do in such a manner as to form a little bulb, which is to be ballasted in the manner described at the article Hydrometers. After having introduced into the case a little ball of cotton, you place therein the thermometer, furnished with its scale, and in such a manner that the reservoir rests on the cotton. You terminate the upper end of the case either with a ring or by a contraction which permits the instrument to be suspended by a cord. See [pl. 4], fig. 4 and 5.
Spiral Thermometer.—Take a tube which is not capillary, but which has thin sides; close one of its ends, and bend it round by pressing it with a metallic rod; continue to bend it round till it has made several turns, all in the same plane. See [pl. 1], fig. 13. The latter turns may be managed with the fingers instead of the metallic rod. When the reservoir so formed is sufficiently large, solder to the end of it a capillary tube, which you point in a direction perpendicular to that of the axis of the spiral. The instrument is represented by [pl. 4], fig. 8.
Pocket Thermometer.—The pocket thermometer differs in nothing from the thermometer just described, except that the capillary tube, instead of passing away from the spiral in a straight line, is turned round, so as to form a continuation of the spiral. See [pl. 4], fig. 17.
Maximum Thermometer.—This instrument consists of an ordinary mercurial thermometer, bent at a right angle near the origin of the reservoir, and in the horizontal column of which a little steel or iron rod has been introduced: this rod, by gliding in the tube, where it experiences very little friction, serves as an index. Since this index does not permit the instrument to be sealed with the vacuum above the mercury, you must terminate the sealing by a little reservoir, as we have described at the article on the second method of closing thermometers. The instrument is represented by [pl. 4], fig. 24.
Minimum Thermometer.—This instrument is constructed pretty nearly in the same manner as the preceding. The liquid, however, must be alcohol, and the index a little rod of enamel, which ought not to be quite so large as the bore of the thermometer tube. You seal the tube by making a vacuum above the column.
Bellani’s Maximum Thermometer.—This thermometer is represented by [pl. 4], fig. 9. Take a tube which is very regular, and about one-eighth or one-twelfth of an inch diameter in the bore; solder a reservoir at each end, one of them much larger than the other; make a bend near the large reservoir, and then fill the instrument with alcohol to A. Above that, place the first index, which consists of a very small piece of tube closed at one end and cut off square at the other. In the interior of this tube the two ends of a hair are fixed, by means of a little rod of iron, which is pushed into the tube. Introduce a quantity of mercury above this index, make the bend B, add again mercury as far as C, then another index similar to the first. Finally, fill the rest of the tube and the half the little reservoir with alcohol, and seal the point.
Differential Thermometer.—This instrument is represented by [pl. 3], fig. 14. Take a tube ten or twelve inches long, and one-eighth or one-twelfth of an inch internal diameter; blow a bulb at one end, and bend the tube at a right angle towards the fourth part of its length. Prepare a second tube in the same manner, and solder the bent ends together, so as to form a single tube with a bulb at each end, having previously poured into one of the bulbs a small quantity of sulphuric acid tinged red.
Instead of following the above method, you may take a single tube of twenty or twenty-four inches in length, and of the above-mentioned diameter; you solder a bulb at each end, bend the tube twice till it represents the figure, pour in the acid, and then seal the open points. The graduation of the differential thermometer, as well as of all the other thermometers, is described in a subsequent section.
Tube for Crystallizing Spermaceti.—Take a little capillary tube; curl one of its ends into a ring, and solder the other to a cylindrical reservoir, two-thirds of the capacity of which you fill with very pure spermaceti dissolved in sulphuric ether; you then seal the point of the reservoir. See [pl. 3], fig. 27.
Tube for demonstrating the non-conductability of Heat by Liquids.—This is represented by [pl. 2], fig. 26. It is a tube sealed at one end, bordered at the other, and bent in such a manner as conveniently to permit the upper part of a column of liquid to be exposed to heat.
Tube for estimating the Density of Vapours.—Represented by [pl. 2], fig. 14. It is merely a tube sealed at one end, bordered at the other, and bent as shewn by the figure.
Tubes for exposing Substances to Heat and Gases.—This instrument consists of a tube bent in the middle into a U. [Pl. 3], fig. 3. It is much employed in chemistry, for containing substances which we wish at the same time to expose to an elevated temperature and to the action of certain gases. This tube can also be employed for cooling gases, or liquids, in distillation; the bent part being, in this case, dipped into water or a freezing mixture, or enveloped in wet paper or cloth.
Tubes for the Preservation of Objects of Natural History, or of Chemical Preparations.—Take a tube of which the width and length corresponds with the object which is to be enclosed; draw it out at one end, and, after having obstructed the point, twist it into a ring. Introduce the object by the open extremity, which you must afterwards draw out; fill the tube with the liquid necessary to preserve the object, and then seal the point. See [pl. 2], fig. 27.
If you desire to have the power of taking out the object at will—as, for example, when grain is preserved, or when, in chemistry, the tube is employed to contain salts and other compounds, of which small quantities are now and then required for use—you do not seal the end of the receiver, but border it in such a manner that it can be closed by a cork.
In some cases a cork is not sufficient to secure the substance from the action of air: it must then be assisted with a little cement. By melting together two parts of yellow wax, one part of turpentine, and a small quantity of Venetian red, a very useful cement for such purposes is obtained.
It is sometimes necessary to suspend the objects enclosed within the tube: you then introduce a little glass hook, the tail of which you solder to the upper extremity of the tube; managing this operation at the same time that you make the external ring for the support of the instrument. By turning the hook round cautiously, which is done when the end of the tube is in a soft state, and by cooling the whole with care, you may succeed in fixing the hook in the centre of the tube. See [pl. 3], fig. 20.
Tube for emptying Eggs.—It is a simple tube, drawn out to a capillary point at one end, and bent there into a V. See [pl. 3], fig. 23.
The application which the author has made of this instrument, and of the tube represented by [pl. 3], fig. 26, has been shewn in a memoir inserted in the Annales des Sciences Naturelles, Tom. XV. Novembre 1828, concerning a new method of preparing and rendering durable collections of eggs destined for cabinets of Natural History.
Vial of the Four Elements.—This instrument is represented by [pl. 2], fig. 27. Take a tube drawn out at one end, obstruct the canal two inches from the extremity, and twist the contracted part into a ring. Draw out the other end of the tube, introduce the proper liquids, remove the point of the tube, and seal it. The liquids generally employed for filling the vial of the four elements are, 1. Mercury; 2. A very concentrated solution of carbonate of potash; 3. Oil of turpentine; 4. Alcohol. A portion of air is also allowed to remain in the tube.
Water Hammer.—[Pl. 2], fig. 18, is a representation of this instrument. Choose a tube of a good diameter, and with thick sides; seal it at one end and draw it out at the other. Blow a bulb at the base of the contracted part; then, having put a quantity of water in the tube, let it boil therein, to expel the atmospherical air. When you imagine that all the air has been expelled, and that nothing remains in the tube but steam and water, seal the open point.
When you have to seal a tube in this manner, you should be careful to draw out the extremity of the tube somewhat abruptly, and leave a very small opening, so that it shall be sufficient to expose the point to the jet of a candle blown by a mouth blowpipe, to have the sealing completely and suddenly effected. You can afterwards round this sealed part by turning it in the flame of the lamp, provided, however, that you have preserved a sufficient thickness of glass at the sides of the point. If you omit to take this precaution, the pressure of the atmosphere, acting with great force on the softened glass when it is unsupported by the partial vacuum within the tube, is capable of producing such a flattening, or even sinking in of the matter, as could not subsequently be rectified; except, indeed, by heating simultaneously the liquid contained in the tube and the glass to be mended, which is an operation of a very delicate description.
Welter’s Safety Tubes.—After having closed a tube at one end and drawn it out at the other, give it the curvature exhibited by plate 3, fig. 18. Pierce it then laterally, in the middle of the part a b, and solder there the extremity of a tube, to the other end of which a funnel has been soldered: it is necessary that the funnel be closed by a cork. The soldering being terminated, a bulb must be blown and the tube bent in S, in the manner shewn by the figure. Then open the closed end, and cut off the contracted point.