Experimental Researches in Chemistry and Physics

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Experimental Researches

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Chemistry and Physics.

Analysis of native caustic lime

Analysis of Native Caustic Lime.

On the native Caustic Lime of Tuscany. By the MARQUIS RIDOLFI.

The interesting communication of Dr. Giovacchino Taddei respecting his discovery of caustic lime in the water of the ancient bath of Santa Gonda, in August 1815, induced me to visit the spot. The following is the result of my researches:—

The bath is situated in a laguna in the corner of a field near the high road to Pisa, which divides the plain called La Catena from the mountains of Cigoli and San. Miniato. The soil is a mixture of clay, calcareous earth, siliceous sand, and vegetable matter. There are two sources of water; one issues from the bottom of the laguna, and the other from the side. The first is hot, raising the thermometer of Reaumur to 35¼°. It is so saturated with lime, that upon cooling the water, it deposits a considerable quantity. It contains also muriate of lime and muriate of soda. The upper spring contains a little carbonic acid gas, some sulphuretted hydrogen, and some sulphate of soda. The following is the manner in which the caustic lime is formed in this bath. The lower spring yields a quantity of lime, but as this spring does not rise freely, but oozes through the bottom of the bath, the lime forms a stratum at the bottom of the lagune; which stratum, absorbing the carbonic acid gas of the water above, passes to the state of a carbonate, and thus forms a defence to the lime, which is continually depositing itself underneath, and prevents it losing its causticity. In fact, the caustic lime is found enclosed between the stratum of the carbonate of lime and the clayey bottom of the laguna.

Signor Taddei found the masses of caustic lime so large, that he could not get them out but by breaking them into pieces. He, however, succeeded in removing the whole of it: and I, having visited the spot two months after, found small incrustations of the same substance newly formed.

Analysis of the native Caustic Lime. By Mr. , Assistant in the Laboratory of the Royal Institution.

This substance came to England in a bottle filled up with water, the atmospherical air being perfectly excluded.

It is almost entirely soluble in muriatic acid without effervescence, leaving nothing but a few light flocculi. The solution, when tested, was found to contain lime and iron.

A clean uniform piece of the substance was dried, as much as could be, by bibulous paper. A fragment of it being heated red, lost 62·26 per cent. of water.

The remainder of the original substance, weighing 188 grains, was dissolved in muriatic acid, and evaporated at a high heat on the sand-bath, acid was again added, and the evaporation repeated. Water was poured on it, and the silica separated: when well washed, dried, and heated red, it weighed 7·5 grains.

The filtered solution was precipitated by carbonate of potash, and the precipitate boiled in solution of pure potash. The solution was separated from the solid matter, neutralized by sulphuric acid, and precipitated by carbonate of ammonia. The precipitate, when well washed and dried, weighed 0·95 of a grain. It was soluble in sulphuric acid, and possessed the properties of alumina.

Diluted sulphuric acid was added to the solid matter not acted upon by the potash; the whole boiled for some time, and then filtered. The sulphate of lime obtained weighed, after being heated red, 136 grains, which, estimating the lime at 43 per cent., is equivalent to 58·48 grains of lime.

The sulphuric solution was precipitated by ammonia, and two grains of oxide of iron were obtained.

Supposing the quantity of water in every part of the piece first taken to be uniform, it would follow that the 188 grains contained 117·05 of water; so that 70·95 was the quantity of dry matter acted upon. The results were—

|Grains.

Silica | | 7·50

Alumina | | 0·95

Lime | | 58·48

Oxide of iron | | 2·00

| 68·93

The loss is therefore rather more than two grains, which may, perhaps, actually have taken place, and the difference may have been derived from the unequal diffusion of water throughout the piece.

Supposing 100 parts of the specimen to have been taken, the analysis will stand thus:—

|Grains.

Lime | | 82·424

Silex | | 10·570

Iron | | 2·820

Alumina | | 1·340

Loss | | 2·846

| 100·000

It is perhaps worthy of observation, that during the solution of the substance in muriatic acid, a part only of the silica separated; the greater part remained in solution until heat was applied, when it gelatinized, as in the case where it is separated by an acid and heat from its combination with alkali.

Observations on the preceding Paper. by Sir , V.P.R.I., F.R.S.

The Duchess of Montrose was so good as to send me the caustic lime which is the subject of the preceding analysis; her Grace received it immediately from Tuscany. It was in a bottle, carefully sealed and full of water. Some of the exterior portions had become combined with carbonic acid before they were collected, and from the colour, it appeared that there were different portions of protoxide of iron in different parts of the substance.

On examining the water, it was found to be a saturated solution of lime, and it contained fixed alkali, but in quantities so minute, that after the lime was separated, it could be made evident only by coloured tests.

It appears from Mr. Faraday's analysis, that the menstruum which deposits the solid substance must be a solution of silica in lime-water, and heat is evidently the agent by which the large quantity of lime deposited is made soluble and is enabled to act on silica; and the fact offers a new point of analogy between the alkalies and the alkaline earths.

Vestiges of extinct volcanoes exist in all the low countries on the western side of the Apennines; and the number of warm springs in the Tuscan, Roman, and Neapolitan States, prove that a source of subterraneous heat is still in activity beneath a great part of the surface in these districts.

Carbonic acid is disengaged in considerable quantities in several of the springs at the foot of the Apennines; and some of the waters that deposit calcareous matter are saturated solutions of this substance. Calcareous tufas of recent formation are to be found in every part of Italy. The well-known Travertine marble, Marmor Tiburtinum, is a production of this kind; and the Lago di Solfaterra near Tivoli, of which I shall give a particular account on a future occasion, annually deposits masses of this stone of several inches in thickness.

It is scarcely possible to avoid the conclusion, that the carbonic acid, which by its geological agency has so modified the surface of Italy, is disengaged in consequence of the action of volcanic fires on the limestone, of which the Apennines are principally composed, and liberated at their feet, where the pressure is comparatively small; but the Tuscan laguna offers the only instance in which the action of these fires extends, or has extended, to the surface at which the water collected in the mountains finds its way to the sea, so as to enable it to dissolve caustic calcareous matter.

Apparatus for the combustion of the diamond

Description of a New Apparatus for the Combustion of the Diamond.

In the course of the experiments which Sir Humphry Davy made at Florence on the combustion of the diamond, he discovered that when the gem began to burn in an atmosphere of pure oxygen, having free access to it on all sides, it would continue burning, though the original source of heat were removed, until the particles were rendered so small as to be too readily cooled by the little platinum tray which supported them. (Philosophical Transactions, 1814, p. 557.) In consequence of this observation, an idea arose, that if the diamond were well heated, and then introduced into oxygen, it would go on burning, and afford an easy method of exhibiting its combustibility. Upon trial this was found to be the case, and a notice to that effect put in this Journal (see shove). Since then, an apparatus of this kind has been perfected, and is now represented in Plate I. fig. 1.

It consists of a glass globe, of the capacity of about 140 cubic inches, furnished with a cap, having a large aperture; the stopcock, which screws into this cap, has a jet A rising from it, nearly into the centre of the globe; this is destined to convey a small stream of hydrogen or other inflammable gas. Two wires, c c, terminate at a very little distance from each other, just above this jet, and are intended to light the stream of hydrogen by electrical sparks; one of them commences from the side of the jet, the other is enclosed and insulated nearly in its whole length in a glass tube: the tube and wire pass through the upper part of the stopcock, and the wire terminates on the outside in a ball or ring, D, at which sparks are to be taken from the machine, either directly or by a chain. On the end of the jet is fixed, by a little socket, a small capsule, B, made of platinum foil. This capsule is pierced full of small holes, and serves as a grate to hold the diamonds. Its distance is about three-quarters of an inch from the end of the jet; and the arm, by which it is supported, is bent round, so that the stream of hydrogen shall not play against it. The stopcock screws, by its lower termination, on to a small pillar fixed on a stand, and at the side of this pillar is an aperture by which a bladder filled with gas may be connected with the apparatus.

On using the apparatus, the diamond is to be placed in the capsule, and then the globe being screwed on to the stopcock, the latter is to be removed from the pillar and placed on the air-pump; the globe is then to be exhausted and afterwards filled with pure oxygen: or, lest the stream of oxygen in entering should blow away the diamond, the globe may be filled with the gas first, and then, dexterously taking out the stopcock for a short time, the diamonds may be introduced and the stopcock replaced. The apparatus is then to be fixed on the pillar, and a bladder of hydrogen gas attached to the aperture. Now, passing a current of sparks between the wires, a small stream of hydrogen is to be thrown in, which inflaming, immediately heats the capsule and diamonds white-hot; the diamonds will then enter into combustion, and the hydrogen may be immediately turned off and the bladder detached. The diamonds will continue to burn, producing a strong white heat, until so far reduced in size as to be cooled too low by the platinum with which they lie in contact.

When the flame of hydrogen is used to heat the diamonds, it is evident a little water will be found in the globe; but this is of no consequence, except in attempts to detect hydrogen in the diamond; the inconvenience may be obviated, if required, by using the flame of carbonic oxide. As, however, no hydrogen has at any time been detected in the diamond, it is better to use that gas as the heating agent; for then the carbonic acid, produced by the combustion, is unmixed with that from any other source, and may be collected, and its quantity ascertained.

Combustion of the diamond

Combustion of the Diamond.

Sir H. Davy was the first to show that the diamond was capable of supporting its own combustion in oxygen without the continued application of extraneous heat, and he thus obviated one of the anomalies exhibited by this body when compared with charcoal. This phenomenon, though rarely observed, is easily exhibited. If the diamond, supported in the perforated cup, be fixed at the end of a jet, so that a stream of hydrogen can be thrown on to it, it is easy, by inflaming the jet, to heat the gem, and whilst in that state to introduce it into a globe or flask containing oxygen. On turning off the hydrogen the diamond enters into combustion, and will remain burning until nearly consumed. The loss of weight in the diamond, the formation of carbonic acid, and the actual combustion are thus very easily shown.

Escape of gases through capillary tubes

On the Escape of Gases through Capillary Tubes.

As the mobility of a body, or the ease with which its particles move among themselves, depends entirely upon its physical properties, little delay would arise in the mind, on a consideration of the probable comparative mobilities of the different gases. These bodies being nearly similar in all the physical properties, except specific gravity, which can interfere with internal motions generated in them, would be supposed to have those motions retarded in proportion as this latter character increased; but as this supposition has not been distinctly verified, the following experiments, though possessed of no peculiar claim to attention, may deserve to be recorded.

The apparatus was a copper vessel of the capacity of 100 cubic inches nearly, to which a condensing gauge was attached. Four atmospheres of the gas to be tried were thrown into it, and then a fine thermometer tube, 20 inches in length, was fixed on by adjusting pieces: the gas was suffered to escape until reduced to an atmosphere and a quarter, and the time noticed by a seconds' pendulum. In this way,—

Carbonic acid gas | required | 156·5 | minutes | to escape.

Olefiant gas | „ | 135·5 | „ | „

Carbonic oxide | „ | 133 | „ | „

Common air | „ | 128 | „ | „

Coal-gas | „ | 100 | „ | „

Hydrogen | „ | 57 | „ | „

These experiments tend to show, that the mobility of the gases tried decreases as their specific gravity increases, and they are corroborated by others made with vanes. A wheel, having small planes attached to it, as radii perpendicular to the plane of motion, was made to rotate by a constant force in atmospheres of different gases, and the times which the motion continued, after the force was removed, diminished as the specific gravity increased; as for instance, in

|Carbonic acid | it continued | |6 | seconds.

|Common air | „ | |8 | „

|Coal-gas | „ | |10 | „

|Hydrogen gas | „ | |17 | „

There is therefore every reason to believe, that the actual relative mobilities of the gases are inversely as their specific gravities.

These experiments have been carried much further, in consequence of some peculiar results obtained at low pressures; but as I have not been able to satisfy myself respecting the causes, and have probably taken a wrong view of the phenomena, I shall refrain from detailing them, and merely observe, that there is no apparent connexion between the passage of gases through small tubes and their densities at low pressures. Olefiant gas then passes as readily as hydrogen, and twice as rapidly as either carbonic oxide or common air, and carbonic acid escapes far more readily than much lighter gases. Similar results are also obtained by diminishing the bore of the tube, and then even at considerable pressures, the effect produced by mobility alone is interfered with by other causes, and different times are obtained. These anomalies depend, probably, upon some peculiar loss or compensation of forces in the tube, and offer interesting matter of discussion to mathematicians.

Lecture on mental education

heat, electricity, magnetism, chemical action and motion is a familiar thought; neither can I perceive any reason why they should be led to exclude, a priori, the cause of gravitation from association with the cause of these other phenomena respectively. All that they are limited by in their various investigations, whatever directions they may take, is the necessity of making no assumption directly contradictory of the conservation of force applied to the sum of all the forces concerned, and to endeavour to discover the different directions in which the various parts of the total force have been exerted.

Those who admit separate forces inter-unchangeable, have to show that each of these forces is separately subject to the principle of conservation. If gravitation be such a separate force, and yet its power in the action of two particles be supposed to be diminished fourfold by doubling the distance, surely some new action, having true gravitation character, and that alone, ought to appear; for how else can the totality of the force remain unchanged? To define the force as " a simple attractive force exerted between any two or all the particles of matter, with a strength varying inversely as the square of the distance, " is not to answer the question; nor does it indicate or even assume what are the other complementary results which occur; or allow the supposition that such are necessary: it is simply, as it appears to me, to deny the conservation of force.

As to the gravitating force, I do not presume to say that I have the least idea of what occurs in two particles when their power of mutually approaching each other is changed by their being placed at different distances; but I have a strong conviction, through the influence on my mind of the doctrine of conservation, that there is a change; and that the phenomena resulting from the change will probably appear some day as the result of careful research. If it be said that twere to consider too curiously to consider so," then I must dissent. To refrain to consider, would be to ignore the principle of the conservation of force, and to stop the inquiry which it suggests:—whereas to admit the proper logical force of the principle in our hypotheses and considerations, and to permit its guidance in a cautious yet courageous course of investigation, may give us power to enlarge the generalities we already possess in respect of heat, motion, electricity, magnetism, to associate gravity with them; and perhaps enable us to know whether the essential force of gravitation (and other attractions)is internal or external as respects the attracted bodies.

Returning once more to the definition of the gravitating power as "a simple attractive force exerted between any two or all the particles or masses qf matter at every sensible distance, but with a STRENGTH VARYING inversely as the square of the distance," I ought perhaps to suppose there are many who accept this as a true and sufficient description of the force, and who therefore, in relation to it, deny the principle of conservation. If both are accepted and are thought to be consistent with each other, it cannot be difficult to add words which shall make "varying strength" and "conservation" agree together. It cannot be said that the definition merely applies to the effects of gravitation as far as we know them. So understood, it would form no barrier to progress; for, that particles at different distances are urged towards each other with a power varying inversely as the square of the distance, is a truth; but the definition has not that meaning; and what I object to is the pretence of knowledge which the definition sets up, when it assumes to describe, not the partial effects of the force, but the nature of the force as a whole.

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Observations on Mental Education.

These observations were delivered as a lecture before His Royal Highness The Prince Consort and the Members of the Royal Institution on the 6th of May, 1854. They are so immediately connected in their nature and origin with my own experimental life, considered either as cause or consequence, that I have thought the close of this volume not an unit place for their reproduction] I take courage, Sir, from your presence here this day, to speak boldly that which is upon my mind. I feared that it might be unpleasant to some of my audience, but as I know that your Royal Highness is a champion for and desires the truth, I will believe that all here are united in the same cause, and therefore will give utterance, without hesitation, to what I have to say regarding the present condition of Mental Education.

If the term education may be understood in so large a sense as to include all that belongs to the improvement of the mind, either by the acquisition of the knowledge of others, or by increase of it through its own exertions, then I may hope to be justified for bringing forward a few desultory observations respecting the exercise of the mental powers in a particular direction, which otherwise might seem out of place. The points I have in view are general, but they are manifest in a striking manner, among the physical matters which have occupied n1y life; and as the latter afford a field for exercise in which cogitations and conclusions can be subjected to the rigid tests of fact and experiment—as all classes employ themselves more or less in the consideration of physical matters, and may do so with great advantage, if inclined in the least degree to profit by educational practices—so I hope that what I may say will find its application in every condition of life.

Before entering upon the subject, I must take one distinction which, however it may appear to others, is to me of the utmost importance. High as man is placed above the creatures around him, there is a higher and far more exalted position within his view; and the ways are infinite in which he occupies his thoughts about the fears, or hopes, or expectations of a future life. I believe that the truth of that future cannot be brought to his knowledge by any exertion of his mental powers, however exalted they may be; that it is made known to him by other teaching than his own, and is received through simple belief of the testimony given. Let no one suppose for a moment that the self-education I am about to commend in respect of the things of this life, extends to any considerations of the hope set before us, as if man by reasoning could find out God. It would be improper here to enter upon this subject further than to claim an absolute distinction between religious and ordinary belief. I shall be reproached with the weakness of refusing to apply those mental operations which I think good in respect of high things to the very highest. I am content to hear the reproach. Yet, even in earthly matters, I believe that the invisible things of Him from the creation of the world are clearly seen, being understood by the things that are made, even His eternal power and Godhead; and I have never seen anything incompatible between those things of man which can be known by the spirit of man which is within him, and those higher things concerning his future, which he cannot know by that spirit.

Claiming, then, the use of the ordinary faculties of the mind in ordinary things, let me next endeavour to point out what appears to me to be a great deficiency in the exercise of the mental powers in every direction; three words will express this great want, deficiency of judgment. I do not wish to make any startling assertion, but I know that in physical matters multitudes are ready to draw conclusions who have little or no power of judgment in the cases; that the same is true of other departments of knowledge; and that, generally, mankind is willing to leave the faculties which relate to judgment almost entirely uneducated, and their decisions at the mercy of ignorance, prepossessions, the passions, or even accident.

Do not suppose, because I stand here and speak thus, making no exceptions, that I except myself! I have learned to know that I fall infinitely short of that efficacious exercise of the judgment which may be attained. There are exceptions to my general conclusion, numerous and high; but if we desire to know how far education is required, we do not consider the few who need it not, but the many who have it not; and in respect of judgment, the number of the latter is' almost infinite. I am moreover persuaded, that the clear and powerful minds which have realized in some degree the intellectual preparation I am about to refer to, will admit its importance, and indeed its necessity; and that they will not except themselves, nor think that I have made my statement too extensive.

As I believe that a very large proportion of the errors we make in judgment is a simple and direct result of our perfectly unconscious state, and think that a demonstration of the liabilities we are subject to would aid greatly in providing a remedy, I will proceed first to a few illustrations of a physical nature. Nothing can better supply them than the intimations we derive from our senses; to them we trust directly; by them we become acquainted with external things, and gain the power of increasing and varying facts, upon which we entirely depend. Our sense-perceptions are wonderful. Even in the observant, but unreflective infant, they soon produce a result which looks like intuition, because of its perfection. Coming to the mind as so many data, they are stored up, and without our being conscious, are ever after used in like circumstances in forming our judgment; and it is not wonderful that man should be accustomed to trust them without examination. Nevertheless, the result is the effect of education: the mind has to be instructed with regard to the senses and their intimations through every step of life; and where the instruction is imperfect, it is astonishing how soon and how much their evidence fails us. Yet, in the latter years of life, we do not consider this matter, but, having obtained the ordinary teaching sufficient for ordinary purposes, we venture to judge of things which are extraordinary for the time, and almost always with the more assurance as our powers of observation are less educated. Consider the following case of a physical impression, derived from the sense of touch, which can be examined and verified at pleasure:—If the hands be brought towards each other so that the tips of the corresponding lingers touch, the end of any finger may be considered as an object to be felt by the opposed finger; thus the two middle fingers may for the present be so viewed. If the attention be directed to them, no difficulty will be experienced in moving each lightly in a circle round the tip of the other, so that they shall each feel the opposite, and the motion may be either in one direction or the other-looking at the fingers, or with eyes employed elsewhere—or with the remaining fingers touching quiescently, or moving in a like direction; all is easy, because each finger is employed in the ordinary or educated manner whilst obeying the will, and whilst communicating through the sentient organ with the brain. But turn the hands half-way round, so that their backs shall be towards each other, and then, crossing them at the wrists, again bring the like fingers into contact at the tips. If it be now desired to move the extremities of the middle fingers round each other, or to follow the contour of one finger by the tip of the opposed one, all sorts of confusion in the motion will ensue; and as the finger of one hand tries, under the instruction of the will, to move in one course, the touched finger will convey an intimation that it is moving in another. If all the fingers move at once, all will be in confusion, the ease and simplicity of the first case having entirely disappeared. If, after some considerable trial, familiarity with the new circumstances have removed part of the uncertainty, then, crossing the hands at the opposite sides of the wrists- will renew it. These contrary results are dependent not on any change in the nature of the sentient indication, or of the surfaces or substances which the sense has to deal with; but upon the trifling circumstance of a little variation from the direction in which the sentient organs of these parts are usually exerted; and they show to what an extraordinary extent our interpretations of the sense impressions depend upon the experience, i. e. the education which they have previously received, and their great inability to aid us at once in circumstances which are entirely new.

At other times they fail us because we cannot keep a true remembrance of former impressions. Thus, on the evening of the 11th of March last, I and many others were persuaded that at one period the moon had a real green colour, and though I knew that the prevailing red tints of the general sky were competent to produce an effect of such a kind, yet there was so little of that in the neighbourhood of the planet, that Iwas doubtful whether the green tint was not produced on the moon by some aerial medium spread before it; until by holding up white cards in a proper position, and comparing them with our satellite, I had determined experimentally that the effect was only one of contrast. In the midst of the surrounding tints, my memory could not recall the true sentient impression which the white of the moon most surely had before made upon the eye.

At other times the failure is because one impression is overt powered by another; for as the morning star disappears when the sun is risen, though still above the horizon and shining brightly a ever, so do stronger phenomena obscure weaker, even when both are of the same kind; till an uninstructed person is apt to pass the weaker unobserved, and even deny their existence.