ART. V. Description of Mr. Cooper's Lamp Furnace, for the Analysis of Organic Bodies.

HAVING had occasion to use Mr. Cooper's lamp for the analysis of organic bodies, described in the last volume of the Transactions of the Society of Arts, and having found it very effectual, we have taken the following account of it from that work, with an abstract of the method of using it; and are enabled by Mr. Cooper's kindness to add the description of some improvements which he has since made on the original apparatus.

Fig. 1. Plate iv. a a and b b, are two long spirit-lamps, each having ten burners and wicks, the burners of each lamp sloping towards those of the other, as seen in the end view, fig. 2. They are placed in a tin tray c c, mounted on four feet. This tray is perforated in the middle the whole length of the lamp, and as wide as e e, fig. 2. The object in sloping the burners is, that they may clear the lamps and approach each other as near as is requisite, yet leave free space for a current of air, the tray being perforated and mounted on feet for this purpose: d d are spring wires at each end of the tray, to receive the tube ƒ ƒ containing the substance to be analyzed, and to hold it over the flames; by pressing the shoulders g g, fig. 2, the wires open to receive the tube, and close on removing the pressure; and should the tube be shorter than the lamps, an additional support on a leaden foot, fig. 3, is placed through the opening e e of the tray to rise between the flames, and hold the end of the tube.

The tubes are coated with copper foil, wrapped spirally round them; if each succeeding fold be on half the other, there will be a double coat of copper all the way, if on two-thirds, there will be three layers of copper, by which the glass tube is prevented from bending when hot, and becomes very uniformly heated. The spirals are continued beyond the end of the tube to reach the support, and leave the end within the flames. The dotted line at h, fig. 4, shews the end of the tube short of the support, the foil is secured at the last coil by binding wire, as at i,

Fig. 5, shews the foil in act of being wrapped on, also the proportion of the space occupied by the materials; first the mixture of oxide of copper with the material to be analyzed, next pure oxide of copper, or copper filings, and lastly asbestos. When the quantity of water formed is considerable, the tube is either. blown into a bulb, as at k, fig. 6, or melted on to one ready pre pared.

Fig. 7, is a long funnel, made by drawing out the end of a tube of suitable thickness at m, till it is long and small enough through n n to reach to the bottom of the tube, and then cutting it off at m, by which liquids may be introduced to the bottom of the tube without soiling the sides.

As the wicks nearest the trough are to be first lighted, and the remainder in succession as the former finish their action, there are upright supports of tin o o fixed on the lamps, one for each space between the burners, against which to rest a slip of tin pp, to prevent the lighted wicks from kindling those next, and it also enables the experimenter to extinguish those which have done duty. In fig. 2, the tin slip p p is shewn by dotted lines reaching from lamp to lamp. Little flat caps are put on each burner when done with, to prevent waste of spirit; fig. 8 shews one of these caps q in its place. rr, fig. 1, is a shelf fixed to the mercurial trough, to hold the lamps; ss, the graduated jar. The pipes, with corks, w w, fig. 2, are the apertures by which the spirit is poured into the lamps; their places only are marked at w w, fig. 1. The whole of this apparatus is made of tin plate.

At first Mr. Cooper operated with a tube of one piece; and the materials being put in when the tube was straight, it was afterward heated and bent at the open extremity, so as to suit the mercurial trough; but this has been improved upon by making the tube shorter and having a bent piece, attached to it by a small flexible tube of caoutchouc, f, fig. 1. It removes the chance of accident from stiffness in the end of the tube, and the tubes being straight," may be used many times in succession.

Mr. Cooper has also used with advantage, at times, the form of

receiver shewn at fig.9; it is about twelve inches long, and one inch in diameter, and being filled with mercury and hung over a basin is ready for use. When containing gas, its quantity is estimated by the graduated scale on the tube, care being taken previously to compensate for any difference of mercurial pressure by inserting the long funnel and cork, fig. 10, into the mouth of the receiver, and pouring mercury into the funnel until it is level with that in the receiver. It is easy afterwards to admit water or solution of potash into the receiver to absorb the carbonic acid, and leave the nitrogen.

The oxide of copper required in using this instrument may be procured either by burning the residuum of verdigris which has been used in the preparation of acetic acid, or by heating plates of copper with access of air, and quenching them in water. Great care should be taken that the oxide be pure, and it should be pulverised and heated in a crucible, stirring at the same time. It may then be sifted, and the different portions preserved apart. The tube used should be of crown or green-bottle glass, fourteen to fifteen inches long, (not so long if the separate bent end piece is used,) and from one to two tenths of an inch internal diameter; it should be clean and dry, one end should be sealed up by a blow-pipe, and then it may be balanced. The substance if volatile is now to be introduced, if solid it may be shaken to the bottom, if fluid it is to be poured in by the funnel, fig. 7. The quantity of substance is then to be ascertained, and a portion of cold oxide of copper introduced, sufficient to absorb the substance if fluid, and cover it about a quarter of an inch; after which recently heated and still warm oxide is to be added to the proper height. Then a portion of recently ignited asbestos is introduced and pressed rather lightly on to the oxide, and occupying from one to two inches. The tube, with its contents, is then to be balanced again, after which it is to be enveloped in the copper foil, (care being taken that the foil does not cover the part containing the asbestos,) and the end piece with its caoutchouc tube is to be fastened on.

The tube is then to be arranged as in the figure, and heat applied; the lamps are to have but short wicks, so that the top of the flame

shall just touch the tube, and only one set will be required, unless the tube be large, as for instance, half an inch in diameter; the lamps. are to be lighted in succession, those nearest the gazometer first.

If the substance to be analyzed be a vegetable salt, or be hygrometric, it must be dried, which is best done in vacuo, but which Mr. Cooper effects also in the following manner. A wide-mouth stoppered bottle is selected, and also a smaller bottle which will easily go into it; a quantity of dry pulverized chloride of calcium is then strewed over the bottom of the larger bottle, and the smaller, containing the substance to be dried is also introduced; a small piece of bibulous paper is moistened with alcohol and put inside the larger phial; it is then lighted, and when it has burned for a second or two, the stopper is put into the bottle, and the vacuum obtained is such that the desiccation goes on very rapidly and effectually.

When substances of this kind are analyzed, they must, of course, be mixed with oxide of copper before they are introduced into the tube; a quantity of pure oxide is then to be put into the tube, and it is as well to add afterwards a small quantity of copper filings or shavings. In heating the tube the wicks are to be lighted as before, but instead of suffering the whole to burn at once, it is as well to leave only three or four in action at a time, extinguishing the others, but taking care to ignite the whole extent of tube at once at the end of the process.

When nitrogen is present in the body to be analyzed it has a tendency to become oxidized at high temperatures by the oxide of copper, and in this case yields erroneous results. To obviate this as much as possible Mr. Cooper has lately used protoxide of copper, instead of peroxide; and though he finds that in certain circumstances this also will impart oxygen to the nitrogen, yet it does so with far greater difficulty than the peroxide: hence in all cases where nitrogen is concerned, the protoxide should be used. The protoxide is prepared by fusing peroxide of copper with copper filings in excess; a mass of protoxide is obtained, which, on being pulverized and sifted is fit for use.

The power of the lamps is such that a thick platinum tube, half an inch in diameter, may be rendered bright red-hot by them.

236

ART. VI. Description of a self-acting Blowpipe. By
Mr. H. B. Leeson.

IT has, I believe, before been observed that bottles of Indian Rubber might be expanded to a considerable size by condensing air into them: I am not, however, aware that bottles so filled with condensed air have been applied to the purposes of a Blowpipe.

The bottles I make use of vary in weight from half to threequarters of a pound, and may be readily procured at the Stationer's. To prepare them they should be boiled in water till completely softened, which, if they are put into water already boiling, will generally be accomplished in ten minutes or a quarter of an hour. They must then be taken out and suffered to cool, when a brass tube may be fitted into the neck of the bottle, having a small cock screwed into it at one end, by which it may be connected with the condensing syringe, and to which the blowpipe jets may be attached. There should be a milled projection on the side of the tube, for the purpose of more firmly attaching the bottle to it, which may be effected by passing a ligature of waxed string round the neck of the bottle on each side of the above-mentioned projection.

The bottle must next be filled with condensed air. After a few strokes of the syringe a blister will be observed to form, which will gradually enlarge till the greatest part of the bottle (which must be selected uniform in substance, and free from defects,) has extended to a similar substance. The condensation should not then be con

tinued farther.

Bottles of the size I have mentioned will generally extend from fourteen to seventeen inches in diameter without bursting; and I have occasionally extended them much beyond these dimensions; but in this the operator must, of course, be entirely directed by his own observations.

The Indian rubber varies in its quality. There is one sort which appears of a blacker hue before extension, but becomes very thin and almost transparent on condensing air into it, whilst there is