Εικόνες σελίδας
PDF
Ηλεκτρ. έκδοση
[ocr errors]
[ocr errors]

adverbs and prepositions), which are combined with others to which they lead are only more or less approximate in accor words to vary or modify their signification. They are, also, dance with the results of experiment, often called Particles. The simple words with which they are There are several cases to be considered in the motion of united, are generally verbs; but often nouns and adjectives are, liquids : viz., the efflux of a liquid-Ist, from an orifice in the by prefixes, converted into verbs. Most of the prefixes are thin wall of a reservoir, the thickness of which is less than separable

, that is, may stand apart from the radicals; some, half the smallest dimension of the orifice ; 2nd, from an orihorvever, are found to be inseparable; some are either separable face of the same kind furnished with an adjutage; 3rd, through or inseparable, according to circumstances.

tubes of large diameter; 4th, through capillary tubes; and (2) The prefixes are themselves, also, either simple or com- 5th, over a channel, as the beds of rivers. We shall particupound; as, Herkommen, to come here or hither; herüberkommen, larly consider four of these cases. to come over here, or hither. In most instances, the prefixes

1. Eflux through orifices in a thin wall; and Liquid Vein.may be translated severally as above; but often they are found Let us first consider the flow of water from the orifice of a to be merely intensive or euphonic. This is likewise often vessel having thin walls or sides. If at any point in such a the case in English: thus, ex (which literally signifies wall we make a small opening, the liquid will issue from it out or out of,) has, in some words the signification very, exo under the action of two forces : 1st, gravity, which acts upon ceedingly or the like; as, exasperate, to make very angry; so a, it in the vertical direction; and 2nd, the pressure of the liquid, in the word ameliorate is merely euphonic, the derivative form which acts perpendicularly to the wall, and proportionally, to (ameliorate) meaning nothing more than the simple one, the depth of the orifice. meliorate.

The jet of the liquid which thus issues from the reservoir is $ 90. SIMPLE PREFIXES SEPARABLE.

denominated the vein. If the orifice is made in the bottom of from, off, down; UbFegen, to set or put down; the reservoir, the action of gravity being in the same direction to depose.

as the interior pressure of the liquid, these two forces are to, at, in, on, towards; Anfangen, to catch at, i.e. to added together, and the vein is vertical and rectilinear. But begin.

if the orifice is made in a wall vertical or inclined, the two Ani, on, upon, up;

Aufgchen, to go up; to rise. forces which act upon the liquid are such that the one is out, out of, from; Ausnchmen, to take out; to vertical, and the other horizontal or oblique in its direction. choose.

In this case, the liquid vein following the direction of the Bek, by, near, with;

Beistehen, to stand by; to as- resultant, takes a curvilinear form, which, abstracting the sist.

resistance of the air, would he exactly that of the curve which there, at;

Dableiben, to remain there, or projectiles describe in a vacuum, and known under the name at, to stay; to persist.

of the parabola. Dar, there, at;

Darreichen, to reach there, i.e. Structure of the Liquid l'ein.-To the investigations of M. to offer.

Savart we owe the following particulars relating to the nature Gin, in, into;

Einkaufen, to buy in ; to pur- of the liquid vein. It is composed of two distinct parts : the chase.

first, which is in contact with the orifice, is completely calm Empor up, upward, on high; Emporheben, to lift up. and transparent, and presents the appearance of the most fort, onward, away, forward; Fortfahren, to drive or bear limped crystal cylinder; the second, on the contrary, is troubled

on; to continue.

and agitated, and presents elongated swells, which are reg 12Gegen, towards, against; Gegenhalten, to hold against; larly arranged at intervals, as shown in fig. 41, and which may to resist; to compare.

be termed protuberances. Sa, in, within ; Inwohucn, to dwell in.

This second part of the vein is not Grim home, at home; Heimifchren, to turn home

continuous; for when opaque wards; to return.

liquid, such as mercury, is made to Szer, hither, here; Herbringen, to bring hither,

flow through the orifice, or alouy.

through the vein. Savart has observed Hin thither, there, away; Hingchen, to go thither, or

that the protuberances are formed of away.

discontinuous globules, elongated in Nit, Vitnehmen, to take with, or

a direction transverse to that of the along.

vein ; and that the contractions or Nach, Nadyfolgen, to follow after; to

nodes are formed, on the contrary, of succeed.

globules elongated in the direction of Nicber down, downwards, under; Niederreißen, to pull down.

the vein itself, as shown in fig. 42. on, over, on account of; Oblicgen, to lie cli, i.e. to ap

He has also observed, by looking at ply one's self to; to be in

the vein in a strong light, that the cumbent on.

limped part is formed of annular for, before ) Vorgeljent, to go before; to

swells which originate near the ori

fice, and are propagated at equal surpass. Wegbleiben, to stay away.

intervals until they reach the troubled

part of the vein where they are sepa3,

Zugeben, to give to; to grant. to, towards;

rated. These swells proceed from periodic pulsations which take place

near the orifice. Their number is in ON PHYSICS OR NATURAL PHILOSOPHY,

the direct ratio of the velocity of

efflux, and in the inverse ratio of the No. XIII.

diameter of the orifice.

ܪ

[graphic]

an

We

see

with ;

after ;

[ocr errors]
[ocr errors]

away, off ;

[ocr errors]

HYDRODYNAMICS.

The pulsations just mentioned may Object of the Science. It has been already stated that hydro

be so rapid as to give rise to a sound, dynamics is that part of Rational Mechanics which treats of the

which is increased by receiving the motion of liquids; and that the part of this science which

vein on any tightened membrane. By particularly treats of the art of conducting and raising water,

producing a sound in unison with that is called hydraulics ; that is, hydraulics is the practical depart

of the vein, by means of a musical ment of hydrodynamics.

instrument, Savart has modified the In hydrodynamics as well as in hydrostatics, liquids are Figs. 41,

vein in such a manner, that the proconsidered to be incompressible, perfectly fluid, and conse- tuberances and nodes have taken a more regular form, and the quently free from all viscosity. But liquids possess these pro- transparent part of the vein has entirely disappeared. He has perties only imperfectly; hence the theoretical consequences also found that the resistance of the air has no effect on the

42.

[ocr errors]

form and dimensions of the vein, or on the number of pulsa- the velocity due to the fall mn, which is the space through tions. He has likewise observed that the structure of the which it would ascend, but for the retardmg circumstances just horizontal or oblique veins does not essentially differ from that mentioned, of Vena Contracta, or the Contraction of the Vein.-When efflux —

Fig. 44, takes place through a circular orifice made in a thin wall or side of a vessel full of water, the liquid vein preserves the circular form in its transverse sections, but the diameter is variable. This diameter is at first equal to that of the orifice, it then rapidly diminishes, and at a distance from the orifice nearly equal to its diameter, the section of the vein is no more than

of that of the orifice. If the direction of the vein is vertical as in fig. 41, the section decreases slowly till it reaches the troubled part. If the direction of the vein is horizontal, the section decreases insensibly. If the angle of inclination of the vein varies from 25° to 45°, the vein preserves nearly the same diameter ; but if it exceeds 45°, the section increases from the part contracted to the part troubled. The part where the diameter of the section reaches its minimum, is called the contracted section.

The contraction of the vein originates in the converging directions which the liquid particles assume in the interior of

The following important corollaries are deduced from the the vessel, when they proceed towards the orifice. This phe- / Theorem of Torricelli: !st. All bodies in a nomenon is rendered visible by putting the water in a trans- with equal velocity, it follows that the velocity of discharge is parent vessel, and mixing small light substances with it independent of the density of the liquid. For example, water which are kept in suspension in it, the orifice being made in a and mercury issue with the same velocity, if the height of the thin wall or side of the vessel. If the orifice be half an inch level above the orifice be the same for both liquids. Esperiin diameter, we see at twice or thrice that distance from it ment, indeed, proves that in the case of equal heights and within the vessel, the substances suspended in the water orifices of the same diameter, equal volumes of these liquids drawn from all parts of the vessel towards the orifice, and are discharged in the same time. 2nd. The velocity of disdescribing curve lines, as if they were attracted towards a centre, charge at the issue of a liquid from the orifice, is proportional as shown in fig. 43. The convergence of the particles which to the square root of the height of the level in the reservoir

above the centre of the orifice. This is, in fact, a consequence Fig. 43.

of the laws of gravity, for we have seen, in a former lesson, that representing the velocity acquired by a moveable which falls in a vacuum by v, and the height of the fall by hi, we have v=V/2gh. The velocity calculated by this formula is called the theoretical velocity.

Theoretical and Effective Discharges. - The voluine of a liquid which is actually discharged from an orifice in one second, is called its effective discharge ; and the volume of a liquid equal to that of a cylinder or prism which has the orifice for its base, and the theoretical velicity above mentioned for its height, is called the theoretical discharge.

The effective discharge is always less than the theoretical

discharge. The effective discharge is in reality the product took place in the interior of the vessel is continued esteriorly, of the contracted section of the vein, and the mean relocity of and the liquid vein is gradually contracted till it reaches the the liquid particles at the instant that they pass this section. point where the particles, by the effect of their mutual action, take a parallel or diverging direction. The vein thus forms a

Fig. 15. species of truncated cone or frustrum, of which the greater base is the orifice, and the smaller base the contracted section.

In the preceding remarks we have supposed that the orifice is of the circular form. If it be polygonal, or of any form different from that of a circle, the vein no longer preserves a section of the same form as the orifice. Its form changes as the vein recedes from the orifice, and continually gives rise to protuberances and nodes.

Thcorcm of Torricelli. --- When a liquid issues from a reservoir ?)y an orifice in a thin wall or plate, the velocity of the discharge is determined by the following theorem :

The liquid J'articles as they issue from the orifice have the same velocity as if they fell freely in a vacuum, from a height equal to the vertical distance from the centre to the upper surface of the liquid in the re ervoir. This theorem was discovered by Torricelli in 1643, and was by him considered as a corollary to the laws of falling bodies established by his master, Galileo. This law can be experimentally proved to be a result of the principle demonstrated in mechanics, viz., that when a body is projected upwards with a given velocity, it will rise to the same height from which it would have fallen in order to acquire that relocity. Thus, when the discharge is made to take place vertically upwards, as represented in fig. 44, the liquid vein reaches very nearly the height of the level of the liquid in the vessel from which it is discharged, and the reason why it does not reach it If the area of the section were the same as that of the orifice, entirely, is the resistance of the air, and the action of the liquid and if the mean velocity were the same as the theoretical particles in falling, which oppose the ascent of the jet. Hence, relocity, the effective discharge would be the same as the at its issue from the orifice n, the liquid spouts upwards with theoretical discharge; but it generally happens either that the

[graphic]
[graphic]
[graphic]
[ocr errors]
[ocr errors]
[ocr errors]

!

[ocr errors]

a very

the reservoir B.

area of the contracted section of the vein is considerablydischarge are those now described. Venturi concluded from smaller than that of the orifice, as in discharges which issue his experiments that these ajutages gave an effective discharge from orifices in a thin wall; or, that the velocity at this section 2-4 times greater than that delivered by an orifice in a thin is less than the theoretical velocity, in consequence of the wall having the same diameter as the smaller base, and 1.46 friction of the liquid particles issuing from orifices pierced in a times greater than the theoretical discharge. The ancient thick wall. Thus, in either case, the effective discharge is Romans were acquainted with the value of these ajutages. less than the theoretical discharge; and in order to reduce the The citizens of Rome, who enjoyed the privilege of drawing a latter to the former, it is necessary to multiply it by a certain certain quantity of water from the public reservoirs, found fraction which is called the co-eficient of correction. From that by the use of these ajutages, the quantity permitted by numerous experiments, it has been found that the effective their privilege might be greatly increased ; and the fraud thus discharge is, in general and at a mean, only two-thirds of the practised became so notorions, that a law was passed to pretheoretical discharge.

vent their use. Constant Efiua.-In a great number of hydraulic experiments,

Eflux through Long and Wide Pipes.- When a liquid flows it is necessary that the velocity of efflux should be constant, through a pipe of great length, the efflux takes place either in that is always the same, and this requires that the height of consequence of the inclination of the pipe, as on an inclined the liquid level above the orifice should be invariable. This plane, or in consequence of a pressure which acts on the liquid result may be obtained in several ways. Ist, by means of a at the orifice of the pipe. In both these cases, the force being sluice, which is so regulated that it opens whenever the water constant, the motion ought to be accelerated. Yet in the reservoir tends to rise above the level, and permits it to short distance from the orifice, it is observed that the motion run off by another channel ; 2nd, by means of a siphon or is uniform, which indicates the existence of a force tending to Marriotte's bottle, instruments which will be described in the destroy or counteract the accelerated velocity which the sequel ; 3rd, by means of the float of M. de Prony. The latter liquid would naturally acquire by the force in question. This apparatus, shown at fig. 45, is composed of a reservoir or vessel force is the resistance arising from the cohesion of the liquid P Q full of water, in which are placed two floats F F, connected particles to each other, and their adhesion to the sides of the with each other by an iron rod, which stretches over the pipe. Besides these resisting forces, there are others which reservoir and is bent at both of its lower extremities in order to arise from turns and contractions in the pipes thèmselves; support a moveable reservoir B, placed under the former. A plate but the former are always by far the most considerable. In A, making part of the wall of the reservoir P Q, is pierced with consequence of these various resistances, the velocity of efflux, orifices of different forms and sizes. A funnel placed under and therefore the discharge through pipes, becomes much lesz these orifices conveys the water which flows from them into than the velocity and discharge through orifices in a thin

According to this arrangement, if one of wall. the orifices of the plate be opened, and if three pounds of water be discharged from it, the weight of the floats is increased Eflux through Capillary Tubes.--The efflux of liquids through by three pounds; therefore, according to the conditions of tubes called capillary (from Lat. capillus, hair) because their equilibrium in floating bodies, laid down in a former lesson, bore or diameter is very small and fine, is of considerable these floats will sink and occupy the space of a quantity of importance in a physiological point of view. Dr. Poiseuille has water equal in volume to the water discharged, so that the made numerous experiments on this subject, varying the level in the reservoir P Q remains constant, and therefore the lengths of the tubes, their diameters or degrees of capillarity, velocity of efflux remains the same.

and the pressures which produce the effux of the liquids

through them. In his experiments on capillary glass tubes, Efflux by Ajutages. A short pipe or tube, see fig. 46, applied ne discovered the three following laws : 1st, in the same tube, to or inserted in the orifice of a reservoir in order to increase the discharge is proportional to the pressure; 2nd, in tubes of the discharge is called an ajutage (French, from Lat, adjutare, to equal lengths and under equal pressures, the discharge is proassist). The form of an ajutage is generally that of a hollow portional to the fourth powers of their diameters ; 3rd, in cylinder, or a truncated hollow cone.

tubes of the same diameter and under the same pressure, the

discharge is in the inverse ratio of the lengths. Fig. 46,

Dr. Poiseuille has observed besides these laws that the velocity of efflux is modified by the nature of the liquid. The nitrate of potassa dissolved in water, causes a more rapid efflux of that liquid. Alcohol, on the contrary, has a retarding effect. The eflux of serum is only half as rapid as that of water; and when alcohol is added to serum, the velocity of efflux is diminished still more; but if to the mixture we add the nitrate of potassa, the serum resumes its original velocity. These different experiments were made with glass tubes; and it became important to know whether the results would be the same in the capillary vessels of organised bodies. Now, in

experimenting on dead animals, which were cooled down to When ajutages are applied to an orifice, results of two kinds the temperature of the surrounding atmosphere, it was found present themselves ; either the liquid vein passes through the by injecting serum into the principal artery of an organ, that ajutage without adhering to its sides, and the discharge the nitrate of potassa increased the eflux in the capillary remains the same as before; or the liquid vein adheres, in organs of dead bodies, in the same manner as in glass tubes ; consequence of the molecular attraction existing between the and that alcohol, on the contrary, retarded it. These facts sides of the tube and the particles of the liquid, and the con- tend, therefore, to prove that the circulation of the blood tracted portion of the vein being

increased by expansion, the in the arteries and the veins follows the same laws as the discharge is likewise increased. The best form of a cylindrical efflux of liquids in capillary tubes. ajutage for increasing the discharge, is that which has its

Jets d'Eau, or Spouts of Water -Streams of water which length from two to three times its diameter, The liquid then spout up with force from an orifice in consequence of the issues with a full flow, and the discharge is increased by about pressure of a liquid column more or less elerated above that one-third part.

orifice, are called jets d'eau. If the orifice be made in the Conical ajutages converging outwardly from the reservoir upper surface of a horizontal wall or tube below the level in increase the discharge still more than the preceding. They the reservoir, the jet is vertical and upwards; if the wall or tube produce very regular jets, and throw them to a greater distance be inclined to the horizon the jet is inclined, and describes a or to a greater height than the cylindrical. Their effects, as curve, which, abstracting the resistance of the air, would be a to discharge and velocity of projection change with the angle paralola. of.convergence, that is, with the angle formed by the produc- According to a principle formerly mentioned, a jet of water tion of two opposite sides of the truncated cone which forms tends to rise to a height equal to that of the level of the water the ajutage. Of all ajutages, those which give the greatest l in the reservoir ; but this is never exactly the case, as it meets

[graphic]
[ocr errors]

with three resistances : 1st, the friction of the water in the of sulphuric acid. Now nine is the precise chemical equiva . tubes or pipes, which destroys a part of the velocity ; 2nd, the lent of water, and forty the precise chemical equivalent of sulresistance of the air; 3rd, the resistance which those liquid phuric acid. A few remarks concerning equivalents have alparticles, falling from the highest part of the jet, present to ready been offered ; I do not expect you, however, to underthose which are ascending.

stand this rather abstruse subject perfectly just yet. I must, In order to obtain the maximum height of a jet, the diameters nevertheless, have you to remember, even though you do not of the tubes must increase with their length-; the tubes must understand it, the following fact: When I say that our strongbe free from all inequalities and all sudden windings; and, the est English oil of vitriol is a compound of one equivalent of orifice of efflux must be made in a thin wall, and have a slight water and one of real sulphuric acid, I do not mean equal inclination in order to avoid the third resistance just men- weights, but equal equivalents; the equivalent of the one being tioned. Such orifices are those which raise the jet to the forty and the other nine, as we have seen. The same remark greatest height, and impart to it the greatest regularity and applies to all similar expressions. Well, then, in order to inditranspari ncy. Conical ajutages also produce jets uniform and cate the kind of hydrate which oil of vitriol is, chemists term transparent, but the height is only about eight or nine-tenths it the protohydrate of sulphuric acid, or protohydrated sulof that produced by orifices in a thin wall. Lastly, cylindri- phuric acid. The Greek word zpūtos means first; that is to çal ajutages produce confused jets, of which the height is only say, this is the first in the ascending scale of many hydrates. about of that which is produced by orifices in a thin wall. From this digression (a necessary one, however) let us now In order that a jet may take the greatest range horizontally, it return to the materials in our fiask-or rather let us investigate, is found by analysis, that when the resistance of the air is by means of a diagram, the changes which have ensued. abstracted from the calculation, the angle which it makes with

The case stands thus :the horizon must be 45°, or half a right angle; that is, mid-way between the horizontal and the vertical directions.

Hydrosulphuric acid
Hydrochloric acid (Hydrogen

Chlorine
Sulphuret of Anti-, Sulphur

{
Antimony

Chloride of antimony LESSONS IN CHEMISTRY.-No. XII.

If the resulting liquid be thrown into water, in certain proporRESUMING the consideration of antimony, I now want the stu- tions, which may be ascertained on trial, a powder (oxide of dent to take a little of the orange or black sulphuret of the antimony) deposits. This powder is, however, readily dislatter : powder it; and having thrown it into a Florence flask, solved by the addition of more hydrochloric, or a sufficient pour upon it some hydrochloric or muriatic acid, known in quantity of tartaric acid. commerce under the name of spirit of salt; applying now to the flask either the naked flame of a spirit-lamp, or, what is pre- water is the type of an important feature in the demeanour of

The precipitate which occurs on throwing the chloride into ferable, the heat of a sand-bath, sulphuretted hydrogen gas antimony solutions, most of which are liable to become decom

posed from the operation of very slight causes. Tartar emetic Fig. No. 1.

is not so prone to be unstable as the others are; it may be mixed with mere water, in any proportions, without throwing down a precipitate; but tea-infusion of galls, or indeed almost any vegetable or animal infusion, throws down, even with it, a copious precipitate. Try these experiments; the results will be found to have an important bearing upon circumstances to be mentioned hereafter. Assume, for example, that a person has taken an injurious dose of tartar emetic, and that the emetic action does not supervene; this is the case sometimes. What would you do? In the first place, propose to yourself the object you would desire to accomplish. There is a general

rule to follow in all these casesma rule which I have already will be evolved, as you will readily discover by its disagreeable into a solid. Give then--if tartar emetic be the poison under

mentioned. It is this:--Convert the poisonous irritating fluid odour; and if a sufficient amount of hydrosulphuric acid have consideration-gire copious draughts of tea; a fluid which, as been added, the whole of the sulphuret will be dissolved. The we have seen, renders tartar emetic insoluble-more insolubie, result of this solution is termed the chloride of antimony, pro- at any rate, than it was originally. curable in commerce under the name of butter of antimony. Let us see what decomposition must have ensued in order to Separation of Antimony from Zinc, Manganese, Cadmium, and furnish us with these results. Sulphuret of antimony is, as its Arsenic.—I trust that the student has sufficiently reflected upon name indicates, and as we demonstrated in our preceding les- the properties of these four metals to recognise an indication of son, a compound of sulphur and antimony.

a process by which this might be accomplished. We have not yet demonstrated the composition of hydro- Firstly, It is evident that arsenic and antimony admit of chloric acid gas ; but its name, if analyzed, evidently points to separation from the other metals by the operation of hydrogen, a compound of chlorine and hydrogen, just as the term hydro- which would remove them in the condition of arseniuretted sulphuric points to something which is a compound of sulphur and antimoniuretted hydrogen gases; and the latter, on comand hydrogen. Remember, therefore, the following general bustion, would deposit the two metals in a mixed crust. Fifact :- Whenever you see the syllabic prefix hydro (before a nally, these metals would be separable from each other by the vowel hydr"), the prefix always means hydrogen-never water, prolonged action of boiling nitric acid, which, as we have seen, the presence of which is expressed, not by the syllabic prefix reduces the antimony to the condition of an insoluble white hydro or hydr', but by the full word, hydrated, or hydrate. powder, and changes the arsenic to soluble arsenic acid. The Thus, for instance, hydro-sulphuric acid is synonymous with latter proposition has not been demonstrated. Nitrate of potsulphuretted hydrogen, indicating the compound of sulphur ash produces this result, as I have explained (p. 42). Nitric and hydrogen; but hydrated sulphuric acid, or hydrate of sul-acid has the same effect; indeed, nitre acts by virtue of its conphuric acid, is a compound of sulphuric acid with water. tained nitric acid. Several other analytical processes suggest Practically we call oil of vitriol sulphuric acid ; really it is hy- themselves from combinations of agencies already discussed; the drated sulphuric acid-or a compound of true sulphuric acid most evident process, however, is that which I have given; and (which is a solid) with water. But you will say-If I take oil my object not being to write a systematic course of analysis, I of vitriol and add more water to it, I get a liquid which is no need not detail the others. onger oil of vitriol, but it is still' hydrated sulphuric acid. Before concluding my remarks on this interesting metal, I Truly-the remark is just; hence has arisen the necessity for will mention a curious fact. Two sulphurets of antimony have certain precise terms. The strongest oil of vitriol which we in been spoken of: there exist others; one an orange-coloured England obtain by our process of manufacture is composed of sulphuret, generated artificially.; the other a black substance, nine parts by weight of water united with forty parts by weight I usually sold as antimony by druggists. Now, different thoug

[graphic]
[ocr errors]

the two are in general appearance, their chemical composition and hard, the new substance, allotropic sulphur, is black, . is precisely the same. Chemistry furnishes us with many ductile, soft ; a substance capable of receiving the most exquisimilar examples, all of which are comprehended under the site impressions ; indeed it is used in practice very advangeneral term allotropism, from the two Greek words allos, tageously for the purpose of copying the impressions of another, and operW, I turn. Thus the diamond, coke, charcoal, medals, coins, &c. and plumbago (the latterly commonly known as black-lead), Judging from the appearance of this body, one might at first have all a composition which is exactly similar. Chemists, imagine it to be something else than sulphur; chemical analysis, indeed, have succeeded in changing the diamond to coke; but however, proves them to be the same. In making the latter the other change, far more interesting than the last, remains assertion, I am aware it must be taken with some qualificato be accomplished. The substance phosphorus, again, the in- tions. The truth is, the contemplation of allotropism leads us flamınable nature of which, in its ordinary state, is so remark- into the metaphysics of chemistry; the very term allotropism able, may be converted into a second state, in which it is no meaning another state is expressive of a change; a change in longer combustible, andi n which it is totally devoid of smell; appearance you have had pointed out to you, but this is not nay, what is still more extraordinary, this allotropic phos- all, there is a change of medical properties, à change as to phorus is totally devoid of all poisonous agency, although com solubility in certain fluids : yet when we come to common phosphorus is a violent poison ; its mere vapours rapidly bine this allotropic sulphur with other bodies, we obtain destroying the jaw-bones of the workmen exposed to their in- exactly the same results that we should have obtained with fluence, and causing a frightful death. Perhaps the question sulphur in the ordinary state. will occur to you of this sort What can be the use of this allotropic phosphorus, a substance which, you tell us, is not

Fig. No. 3, inflammable: True, allotropic phosphorus is not inflammable; but, if heated beyond a certain temperature, this curious substance changes into the ordinary form. Now the mere friction of a phosphorus match is sufficient to generate this amount of heat; so, practically, allotropic phosphorus may be employed for the purpose of making matches. In England these matches of allotropic phosphorus have not as yet come much into use ; but on the continent, especially in Prussia, they are common enough.

Whilst on the subject of allotropism, I will furnish you with another example as afforded by sulphur. Take some common sulphur (brimstone), put it into a Florence flask, and apply heat either by means of a spirit-lamp, or, what is preferable in this case, by a flowerpot charcoal furnace already described in a previous lesson, and here represented, No. 2. The sulphur - fuses, giving rise to a limpid fluid, which retains this character

[graphic]

Pig. No. 2.

[graphic]

The most elegant way of demonstrating the characteristics of allotropic sulphur, consists in pouring it in a small continuous stream into a basin of water, which contains a funnel, and around the latter in this way a thread of the substance may be obtained, in appearance very much ike a. thread of india-rubber, No. 3.

The various phenomena of allotropism are directly at variance with the chemical doctrine long accepted, that identity of composition must necessarily accompany identity of chemical effects; and, curiously enough, these same phenomena are favourable to the idea of metallic transmutation, that longcherished hope of the alchemists.

LESSONS IN ITALIAN GRAMMAR.-No. XI.

Di.

By CHARLES TAUSENAU, M.D.,
Of the University of Paria, and Professor of the German and Italian

Languages at the Kensington Proprietary Grammar School.

The proper use of the words di, a, da, in, con, per, su, -pra, until every portion of the sulphur becomes melted., Keeping shall devote this section to an elementary explanation of some

fra, and tra, is of such primary importance in Italian, that I your eye on the fiask, observe the period at which this perfect of their peculiarities. fusion of the sulphur takes place : being accomplished, remove the flask, and pour a little of the fused contents into water. The melted sulphur solidifies as a matter of course, and you get The use of this word very frequently coincides with the use a result identical in every respect with the sulphur before it of the case-sign, or preposition of, in English grammar:was fused; that is to say, the result is brittlemis yellow; I. When the questions of whom? of which of what? physically and chemically similar in point of fact. Replace whose ? what kind or sort of require the genitive also in now the sulphur over the source of heat, and remark the English ; e. g. L'a--re del -dre, the love of the father; changes which ensue. You will first observe a change of i paé-si del prín-ci-pe, the countries of the prince : la cle-mên, colour: the fluid becomes dark, almost black. You will next za di Di-o, the clemency of God; la gran-déz-za dél-la cit-, observe a change of aggregation, the material becomes thick, the greatness of the town; il li-bro di Giá-co-mo, the book of thicker still, and in a few instants a solid. By dexterous James. management it is possible to remove the flask whilst its contents II. When geographical or other proper names indicating are thus solid. Try to do so.

possession, domain, authorship, &c., or merely for the purpose Replace the flask once more, and observe the result; the of defining them, are joined to other nouns; e. g. la cit-di dark solid liquifies once more, and the liquid still remains Ve-ne-zia, the city of Venice; il -gno di Spa-gna, the kingblack; pour some of this liquid into water, and a curious result dom of Spain ; il -se di -glio, the month of July; il no-me will be obtained. Instead of ordinary sulphur, yellow, brittle, I di Fran--sco, the name of Francis ; l' &-so la di Cor-, the

« ΠροηγούμενηΣυνέχεια »