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Scientific American Supplement, No. 508, September 26, 1885
Author: Various
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Fig. 1 represents one form of the new device. Here, a is the copper or silver wire, and b is a soldering made with a very fusible metal and securing a continuity of the circuit. Each extremity of the wire, a, is connected with a heavy ring, c, of copper or other good conducting metal. The hook, d, with which the upper ring, c, is in contact, communicates metallically with one of the extremities of the conductor at the place where the latter is interrupted for the insertion of the circuit cutter. The hook, e, with which the lower ring, c, is in contact, tends constantly to descend under the action of a spiral spring, f, which is connected metallically with the other extremity of the principal conductor. The hooks, d and e, are arranged approximately in the same vertical plane, and have a slightly rounded upper and lower surface, designed to prevent the rings, c, of the fusible wire, a, from escaping from the hooks. In Fig. 1 the position of the arm, e, when there is no fusible wire in circuit, is shown by dotted lines. When this arm occupies the position shown by entire lines, it exerts a certain traction upon the soldering, b, and separates the two halves of the wire, a, as soon as the intensity of circulation exceeds its normal value. The mode of putting the wire with fusible soldering into circuit is clearly shown in the engraving.



Fig. 2 shows a different mode of mounting the wire. The wire, q, is soldered in the center, and is bent into the shape of a U, and kept in place by the pieces, r and s. In this way the two ends of it tend constantly to separate from each other. Messrs. Thomson & Bottomley likewise employ weights, simply, for submitting the wire to a constant stress. The apparatus is inclosed in a box provided with a glass cover.—La Lumiere Electrique.

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NEW MICRO-TELEPHONIC APPARATUS.

Despite the simplicity of their parts, and the slight value of the materials employed, the existing micro-telephonic apparatus keep at relatively high prices, and the use of them is often rejected, to the benefit of speaking tubes, when the distance between stations is not too great. We propose to describe a new style of apparatus that are in no wise inferior to those in general use, and the price of which is relatively low.

The microphone transmitter may have several forms. The most elementary of these consists of two pieces of carbon, from one to one and a quarter inches in length by one-half inch in width, between which are fixed two nails, about two inches in length, whose extremities, filed to a point, enter small conical apertures in the carbons. Fig. 1 gives an idea of the arrangement.



Fig. 2 represents a model which is a little more complicated, but which gives remarkable results. The largest nail is here two inches in length, and the shortest three-quarter inch.



The receivers may be Bell telephones of the simplest form found in the market (Fig. 3); but for these there may be substituted a bar of soft iron, cast iron, or steel, one of the extremities of which is provided with a bobbin upon, which is wound insulated copper wire 0.02 inch in diameter. The apparatus is mounted like an ordinary Bell telephone. A horseshoe electro may also be used, and the poles be made to act (Fig. 4). The current sent by the transmitter suffices to produce a magnetic field in which the variations in intensity produced by the microphone succeed perfectly in reproducing speech and music. With four Leclanche elements, the sounds are perceived very clearly. The elements used may be bichromate of potash ones, those of Lelande and Chaperon, etc.



To this apparatus there may be added a second bobbin of coarser wire into which is passed a current from a local pile. This produces a much intenser magnetic field, and, consequently, louder sounds. This modification, however, is really useful only for long distances.

Any arrangement imaginable may be given the transmitter and receiver; but, aside from the fact that the ones just indicated are the simplest, they give results that are at least equal, if not superior, to all others.

We shall insist here only upon the arrangement of the microphone, which is new (at least in practice), and upon the uselessness of having well magnetized steel bars and wires of extreme fineness in the receiver.



We have stated that the nail microphones are the simplest. The nails may be replaced by copper or any other metal, or they may be well nickelized; but common nails answer very well, and do not oxidize much. An apparatus of this kind (Fig. 5) that has been for more than a year in a laboratory filled with acid vapors is yet working very well. These apparatus possess the further advantage of being very strong, and of undergoing violent shocks without breaking or even getting out of order. They may be used either with or without induction coils. We have not yet measured their range, but can cite the following fact:

One of these apparatus, quite crudely mounted, was put into a circuit with a resistance of 300 ohms. With a single already exhausted bichromate element, giving scarcely 2 volts, musical sounds and speech reached the receiver without being notably weakened. Such resistance represents a length of eighteen miles of ordinary telegraph wire. After this, 700 ohms were overcome with 3.4 volts. This result was obtained by direct transmission, and without an induction coil, and it is probable that it might be much exceeded without sensibly increasing the electromotive force of the current.—Le Genie Civil.

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MESSRS. KAPP AND CROMPTON'S MEASURING INSTRUMENTS.

We give herewith, from the Elektrotechnische Zeitschrift, a few interesting details in regard to the measuring apparatus of Messrs. Kapp and Crompton.

It is evident that when we use permanent magnets or springs as directing forces in measuring instruments, we cannot count upon an absolute constancy in the indications, as the magnetism of the magnetized pieces, or the tension of the springs, modifies in time. The apparatus require to be regulated from time to time, and hence the idea of substituting electro-magnets for permanent ones.



If we suppose (Fig. 1) a magnetized needle, _n s_, placed between the extremities of a soft iron core, N S, and if we group the circuit in such a way that the current, after traversing the coil, _e e_, of the electro, traverses a circle, _d d_, situated in a plane at right angles with the plane of the needle's oscillation, it is evident that we shall have obtained an apparatus that satisfies the aforesaid conditions. It seems at first sight that in such an instrument the directing force should be constant from the moment the electro was saturated, and it would be possible, were sufficiently thin cores used, to obtain a constancy in the directing magnetic field for relatively feeble intensities. In reality, the actions are more complex. The needle, _n s_, is, in fact, induced to return to its position of equilibrium by two forces, the first of which (the attraction of the poles, N S) rapidly increases with the intensity so as to become quickly and perceptibly constant, while the second (the sum of the elementary electrodynamic actions that are exerted between the spirals, _e e_, and the needle, _n s_) increases proportionally to the intensity of the current. If we represent these two sections graphically by referring the magnetic moments as ordinates and the current intensities as abscissas to two co-ordinate axes (Fig. 2), we shall obtain for the first force the curve, O A B, which, starting from A, becomes sensibly parallel with the axis of X, and for the second the right line, O D. The resultant action is represented by the curve, O E E'_F. It will be seen that this action, far from being constant, increases quite rapidly with the intensity of the current, so that the deflections would become feebler and feebler for strong intensities, of current; and this, as well known, would render the apparatus very defective from a practical point of view.



But the action of the spirals can be annulled without sensibly diminishing the magnetism of the core by arranging a second system of spirals identical with the first, but placed in a plane at right angles therewith, or, more simply still, by having a single system of spirals comprising the coil of the electro-magnet, but distributed in a plane that is oblique with respect to the needle's position of rest. It then becomes possible, by properly modifying such angle of inclination, to obtain a total directing action that shall continue to increase with the intensity, and which, graphically represented, shall give the curve, O G G'_H, for example (Fig. 2).



This arrangement, which is adopted in Mr. Kapp's instruments, gives very good results, as may be easily seen by reference to Figs. 3 and 4, in which the current intensities or differences of potential are referred as ordinates and the degrees of deflection of the needle as abscissas. The unbroken lines represent the curves obtained with the apparatus just described, while the dotted ones give the curve of deflection of an ordinary tangent galvanometer. These curves show that for strong intensities of current Mr. Kapp's instrument is more advantageous than the tangent galvanometer. Mr. Crompton has constructed an amperemeter upon the same principle, which is shown in Fig. 5.—La Lumiere Electrique.

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THE CHEMICAL ACTION OF LIGHT.

Professor A. Vogel, in a communication to the "Sitzungsberichte der Munchener Akademie," brings into prominence the fact that the hemlock plant, which yields coniine in Bavaria, contains none in Scotland. Hence he concludes that solar light plays a part in the generation of the alkaloids in plants. This view is corroborated by the circumstance that the tropical cinchonas, if cultivated in our feebly lighted hothouses, yield scarcely any alkaloids. Prof. Vogel has proved this experimentally. He has examined the barks of cinchona plants obtained from different conservatories, but has not found in any of them the characteristic reaction of quinine. Of course it is still possible that quinine might be discovered in other conservatory-grown cinchonas, especially as the specimens operated upon were not fully developed. But as the reaction employed indicates very small quantities of quinine, it may be safely assumed that the barks examined contained not a trace of this alkaloid, and it can scarcely be doubted that the deficiency of sunlight in our hothouses is one of the causes of the deficiency of quinine.

It will at once strike the reader as desirable that specimens of cinchonas should be cultivated in hothouses under the influence of the electric light, in addition to that of the sun.

If sunlight can be regarded as a factor in the formation of alkaloids in the living plant, it has, on the other hand, a decidedly injurious action upon the quinine in the bark stripped from the tree. On drying such bark in full sunlight the quinine is decomposed, and there are formed dark-colored, amorphous, resin-like masses. In the manufacture of quinine the bark is consequently dried in darkness.

This peculiar behavior of quinine on exposure to sunlight finds its parallel in the behavior of chlorophyl with the direct rays of the sun. It is well known that the origin of chlorophyl in the plant is entirely connected with light, so that etiolated leaves growing in the dark form no chlorophyl. But as soon as chlorophyl is removed from the sphere of vegetable life, a brief exposure to the direct rays of the sun destroys its green color completely.

Prof. A. Vogel conjectures that the formation of tannin in the living plant is to some extent influenced by light. This supposition is supported by the fact that the proportion of tannin in beech or larch bark increases from below upward—that is, from the less illuminated to the more illuminated parts, and this in the proportions of 4:6 and 5:10.

Sunny mountain slopes of a medium height yield, according to wide experience, on an average the pine-barks richest in tannin. In woods in level districts the proportion of tannin is greatest in localities exposed to the light, while darkness seems to have an unfavorable effect. Here, also, we must refer to the observation that leaves exceptionally exposed to the light are relatively rich in tannin.

We may here add that in the very frequent cases where a leaf is shadowed by another in very close proximity, or where a portion of a leaf has been folded over by some insect, the portion thus shaded retains a pale green color, while adjacent leaves, or other portions of the same leaf, assume their yellow, red, or brown autumnal tints. If, as seems highly probable, these tints are due to transformation products of tannin, we may not unnaturally conclude that they will be absent where tannin has not been generated.—Jour. of Science.

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EUTEXIA.[1]

[Footnote 1: Read before the Birmingham Philosophical Society, January 22, 1885.]

By THOMAS TURNER, Assoc. R.S.M., F.C.S., Demonstrator of Chemistry, Mason College.

There are a number of interesting facts, some of which are known to most persons, and many of them have been long recognized, of which, however, it must be owned that the explanation is somewhat obscure, and the connections existing between them have been but recently pointed out. As an example of this, it is well known that salt water freezes at a lower temperature than fresh water, and hence sea-water may be quite liquid while rivers and ponds are covered with ice. Again, it is noticed that mixtures of salts often have a fusing-point lower than that of either of the constituent salts, and of this fact we often take advantage in fluxing operations. Further, it is well known that certain alloys can be prepared, the melting-points of which are lower than the melting-point of either of the constituent metals alone. Thus, while potassium melts at 62.5 deg. C., and sodium at about 98 deg., an alloy of these metals is fluid at ordinary temperatures, and fusible metal melts below the temperature of boiling water, or more than 110 deg. lower than the melting-point of tin, the most fusible of the three metals which enter into the composition of this alloy. But though these and many similar facts have been long known, it is but recently, owing largely to the labors of Dr. Guthrie, that fresh truths have been brought to light, and a connection shown to exist throughout the whole which was previously unseen, though we have still to acknowledge that at present there is much at the root of the matter which is but imperfectly understood. Still Dr. Guthrie proves a relationship to exist between the several facts we have previously mentioned, and also between a number of other phenomena which at first sight appear to be equally isolated and unexpected, and we are asked to regard them all as examples of what he has called "eutexia."

We may define a eutectic substance as a body composed of two or more constituents, which constituents are in such proportion to one another as to give to the resultant compound body a minimum temperature of liquefaction—that is, a lower temperature of liquefaction than that given by any other proportion.[2] It will be seen at once by this definition that the temperature of liquefaction of a eutectic substance is lower than the temperature of liquefaction of either or any of the constituents of the mixture. And, further, it is plain that those substances only can be eutectic which we can obtain both as liquid and solid, and hence the property of eutexia is closely connected with solution.

[Footnote 2: Guthrie, Phil. Mag. [5], xvii., p. 462.]

Following in the natural divisions adopted by Dr. Guthrie, we may consider eutexia in three aspects:

I. CRYOHYDRATES.

If a dilute aqueous saline solution be taken at ordinary temperatures, and then slowly cooled to some point below zero on the Centigrade scale, the following series of changes will in general be observed: On reaching a point below zero, the position of which is dependent upon the nature of the salt and the amount of dilution, it will be found that ice is formed; this will float upon the surface of the solution, and may be readily removed. If the ice so removed be afterward pressed, or carefully drained, it will be found to consist of nearly pure water, the liquid draining away being a strong saline solution which had become mechanically entangled among the crystals of ice during solidification. If we further cool the brine which remains, we notice a tolerably uniform fall of temperature with accompanying formation of ice. But at length a point is reached at which the temperature ceases to fall until the whole of the remaining mother-liquor has solidified, with the production of a compound called a cryohydrate,[3] which possesses physical properties different from those of either the ice or the salt from which it is formed.

[Footnote 3: Guthrie, Phil. Mag., 4th Series, xlix., pp. 1, 206, 266; 5th Series, i., pp. 49, 354, 446, vi., p. 35.]

If, on the other hand, we commence with a saturated saline solution, in general it is noticed on cooling the liquid a separation of salt ensues, which salt sinks to the bottom of the mass, and may be removed. The salt so separating may be either anhydrous or a "hydrate" of greater concentration than the mother-liquor. So long as this separation proceeds the temperature falls, but at length a point is reached at which the thermometer remains stationary until the whole is solidified, with the production of a cryohydrate. This temperature of solidification is the same whether we start with a dilute or a saturated solution, and the composition of the cryohydrate is found to be constant. The temperature of production of the cryohydrate is identical with the lowest temperature which can be produced on employing a mixture of ice and the salt as a freezing mixture or cryogen.

It will be readily seen that in the formation of a cryohydrate we have an example of eutexia, since the constituents are present in such proportion as to give to the resultant compound body a minimum temperature of liquefaction.

II. EUTECTIC SALT ALLOYS.[4]

[Footnote 4: F. Guthrie, Phil. Mag. [5], xvii., p. 469; F.B. Guthrie, Journ. Chem. Soc,. 1885, p. 94.]

Although it has been long known that on mixing certain salts the resulting substance possessed a lower melting-point than either of the constituent salts alone, still but few determinations of the melting-points of mixtures of salts have been made, and even these are often of small value, on account of the very considerable range of temperature observed during solidification. This is due largely to the fact that eutectic mixtures were not known, as equivalent proportions of various salts have been employed, while eutectic mixtures are seldom found to possess any simple arithmetical molecular relationship between their constituents.

Eutectic salt alloys closely resemble cryohydrates in behavior. If for simplicity we confine our attention to a fused mixture of two salts in any proportion other than eutectic, it is found that, on cooling, the thermometer falls steadily, until at length that salt which is in excess of the proportion required for a eutectic mixture begins to separate out. If this is removed, the thermometer falls until a fixed point is reached at which the temperature remains stationary until the whole of the mixture solidifies. On remelting, the temperature of solidification is found to be quite fixed, and the mixture is evidently eutectic.

It is of interest to notice that from our knowledge of the cryohydrates it becomes possible to predict the existence, composition, and temperature of solidification of a eutectic alloy, if we are previously furnished with the melting-points of mixtures of the substances in question. Or, in other cases, we may predict from the curve of melting-points that no eutectic alloy is possible.

As an example, we may take the determinations of the melting-points of mixtures of potassium and sodium nitrate by M. Maumene.[5] These are graphically represented in Fig. 1, the curve being derived from the mean of the temperatures given in the memoir. From this diagram we should be led to expect a eutectic mixture, since the curve dips below a horizontal line passing through the melting-point of the more fusible of its constituents. From our curve we should expect a eutectic mixture with about 35 per cent. KNO_{3}, and with a temperature of solidification below 233 deg.. Dr. Guthrie gives 32.9 per cent. at 215 deg.. This agreement is as good as might be expected when one remembers that the melting-points, not being of eutectic mixtures, are difficult to determine, and a considerable range is given; that analyses of mixtures of potassium and sodium salts are apt to vary; and that the two observers differ by +-7 deg. in the temperatures given for the melting-points of the original salts.

[Footnote 5: Comptes Rendus, 1883, 2, p. 45.]



Dr. Tilden has drawn my attention to an interesting example of the lowering of melting-point by the mixture of salts. The melting-point of monohydrochloride of turpentine oil is 125 deg., while that of the dihydrochloride is 50 deg.; but on simply stirring together these compounds in a mortar at common temperatures, they immediately liquefy. Two molecules of the monohydrochloride and one molecule of the dihydrochloride form a mixture which melts at about 20 deg..

III. EUTECTIC METALLIC ALLOYS.

Although many fusible alloys have been long known, I believe no true eutectic metallic alloy had been studied until Dr. Guthrie[6] worked at the subject, employing the same methods as with his cryohydrates. It is found if two metals are fused together and the mixture allowed to cool, that the temperature falls until a point is reached at which that metal which is present in a proportion greater than is required to form the eutectic alloy begins to separate. If this solid be removed as it forms, the temperature gradually falls until a fixed point is reached, at which the eutectic alloy solidifies. Here the thermometer remains stationary until the whole has become solid, and, on remelting, this temperature is found to be quite fixed. In addition to the di-eutectic alloys, we have also tri- and tetra-eutectic alloys, and as an example of the latter we may take the bismuth-tin-lead-cadmium eutectic alloy, melting at 71 deg..

[Footnote 6: Phil. Mag., 5th Series, xvii., p. 462.]

We have already seen with salt eutectics that, given the curve of melting-points of a mixture in various proportions, we may predict the existence, composition, and melting-point of the eutectic alloy. As a matter of course, the same thing holds good for metallic eutectics. An interesting example of this is furnished by the tin-lead alloys, the melting-points of which have been determined by Pillichody.[7] From these determinations we obtain the curve given in Fig. 2, and from this curve, since it dips below a horizontal line passing through the melting-point of the more fusible constituent, we are at once able to predict a eutectic alloy. We should further expect this to have a constitution between PbSn{3} and PbSn{4} and a melting-point somewhat below 181 deg.. On melting together tin and lead, and allowing the alloy to cool, we find our expectation justified; for by pouring off the fluid portion which remains after solidification has commenced, and repeating this several times with the portion so removed, we at length obtain an alloy which solidifies at the constant temperature of 180 deg., when the melting-point of tin is taken as 228 deg.. On analysis 1.064 grm. of this alloy gave 0.885 grm. SnO{2}, which corresponds to Sn 65.43 per cent., or PbSn{3.3}. This, therefore, is the composition of the eutectic alloy, and it finds its place naturally on the curve given in Fig. 2.

[Footnote 7: Dingler's Polyt. Journ., 162, p. 217; Jahresberichte, 1861, p. 279.]



It will be seen that the subject of eutexia embraces many points of practical importance and of theoretical interest. Thus it has been shown by Dr. Guthrie that the desilverizing of lead in Pattinson's process is but a case of eutexia, the separation of lead on cooling a bath of argentiferous lead poor in silver being analogous to the separation of ice from a salt solution. Dr. Guthrie has also shown that eutexia may reasonably be supposed to have played an important part in the production and separation of many rock-forming minerals.

It is with considerable diffidence that I suggest the following as an explanation of the multitude of facts to which previous reference has been made.

In a mixture of two substances, A and B, we have the following forces active, tending to produce solidification:

1. The cohesion between the particles of A.

2. The cohesion between the particles of B.

3. The cohesion between the particles of A and the particles of B.

With regard to this last factor, it will be seen that there are three cases possible:

1. The cohesion of the mixture A B may be greater than the cohesion of A + the cohesion of B.

2. The cohesion of A B may be equal to the cohesion of A + the cohesion of B.

3. The cohesion of A B may be less than the cohesion of A + the cohesion of B.

Now, since cohesion tends to produce solidification, we should in the first case expect to find the melting-point of the mixture higher than the mean of the melting-points of its constituents, or the curve of melting-points would be of the form given in a, Fig. 3. Here no eutectic mixture is possible.



In the second case, where cohesion A B = cohesion A + B, we should obtain melting-points for the mixture which would agree with the mean of the melting-points of the constituents, the curve of melting-points would be a straight line, and again no eutectic mixture would be possible.

In the third case, however, where cohesion A B is less than cohesion A + B, we should find the melting-points of the mixture lower than the mean of the melting-points of its constituents, and the curve of melting-points would be of the form given in e, Fig. 3. Here, in those cases where the difference of cohesion on mixture is considerable, the curve of melting-points may dip below the line e f. This is the only case in which a eutectic mixture is possible, and it is, of course, found at the lowest point of the curve.

If it be true, as above suggested, that the force of cohesion is at its minimum in the eutectic alloy, we should expect to find, in preparing a eutectic substance, either that actual expansion took place, or that the molecular volume would gradually increase in passing along our curve of melting-points, from either end, for each molecule added, and that it would obtain its greatest value at the point corresponding to the eutectic alloy.

Of this I have no direct evidence as yet, but it is a point of considerable interest, and I may possibly return to it at some future time.—Chemical News.

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CHINOLINE.

Dr. Conrad Berens, of the University of Pennsylvania, reaches the following:

1. Chinoline tartrate is a powerful agent, producing death by asphyxia.

2. The drug increases the force and frequency of the respirations by stimulating the vagus roots in the lung.

3. It paralyzes respiration finally by a secondary depressant action upon the respiratory center.

4. It does not cause convulsions.

5. It lessens and finally abolishes reflex action by a direct action upon the cord, and by a slight action upon the muscles and nerves.

6. It diminishes or abolishes muscular contractility respectively when applied through the circulation or directly.

7. It coagulates myosin and albumen.

8. It causes insalivation by paralysis of the secretory fibers of the chorda tympani; increases the flow of bile; has no action upon the spleen.

9. It lowers blood-pressure by paralyzing the vaso-motor centers and by a direct depressant action upon the heart muscle.

10. It diminishes the pulse rate by direct action upon the heart.

11. It lowers the temperature by increasing the loss of heat.

12. It is a powerful antiseptic; and, finally,

13. Its paths of elimination are not known.

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METHOD FOR RAPID ESTIMATION OF UREA.

Being called upon to make a good many brief and rapid analyses of urine on "clinic days" of our medical department, I devised the following modification of Knop's method of estimating urea; and after using it for a year with perfectly satisfactory results, venture to describe and recommend it as especially adapted for physicians' use, by reason of simplicity, cheapness, and accuracy. In perfecting and testing it I was assisted greatly by J. Torrey, Jr., then working with me.



The apparatus consists of the glass tube, A, which is about 8 cm. long and 21/2 cm. in diameter, joined to the tube, B, which is about 25 or 30 cm. in length in its longer arm and 8 or 10 in its shorter, and has a diameter of about 5 mm. Near the bend is an outlet tube, c, provided with "ball valve" or pinch cock. d, e, f, g, are marks upon the tubes. C is a rubber cork with two holes through which the bent tube, D, passes. D is of such size and length as to hold about 1 c.c., and one of its ends may be a trifle longer than the other.

The apparatus is used as follows: Remove the cork and pour in mercury until it stands at e and g, then fill up to the mark, f, with sodium or potassium hypobromite (made by shaking up bromine with a strong solution of sodium or potassium hydroxide). Next carefully fill the tube in the cork with the urine, being careful especially not to run it over or leave air bubbles in it. This can easily be done by using a small pipette, but if accidentally a little runs over, it should be wiped off the end of the cork with blotting paper. The cork is then to be inserted closely into the tube; the urine tube being so small, the urine will not run out in so doing. The mercury is then drawn out through c till it stands in B at d. Its level in A will of course not be changed greatly. Now, incline the apparatus till the surface of the hypobromite touches the urine in the longer part of the urine tube, and then bring it upright again. The urine will thus be discharged into the hypobromite, which will of course decompose the urea, liberating nitrogen, which will cause the mercury to rise in B. Shake until no further change of level is seen, and mark the level of mercury in B with a rubber band, then remove the cork, draw out the liquid with a pipette, dry out the tube above the mercury with scrap of blotting paper, pour back the mercury drawn out, and repeat the process to be sure that no error was made.

If now two or three marks have been made upon the tube, B, indicating the height of the mercury when solutions containing known per cents. of urea are used, an accurate opinion can be at once formed as to the condition of the urine as regards urea.

As is well known, normal urine contains about 2.5-3 per cent. of urea, so that graduations representing 2, 2.5, 3, and 4 per cent. are usually all that are needed, though of course many more can be easily made.

The results obtained with this apparatus have been repeatedly compared with those of more elaborate ones, and no practical difference observed. Evidently the same apparatus, differently graduated, might be employed to determine the carbonate present in such a substance as crude soda ash or other similar mixture. In such a case the weighed material would be put upon the mercury with water and the small tube filled with acid.

Bowdoin College Chemical Laboratory.—F.C. Robinson, in Amer. Chem. Jour.

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