Chapter 7

A new and most valuable method of determining the molecular weights of non-volatile as well as volatile substances has just been brought into prominence by Prof. Victor Meyer (_Berichte_, 1888, No. 3). The method itself was discovered by M. Raoult, and finally perfected by him in 1886, but up to the present has been but little utilized by chemists. It will be remembered that Prof. Meyer has recently discovered two isomeric series of derivatives of benzil, differing only in the position of the various groups in space. If each couple of isomers possess the same molecular weight, a certain modification of the new Van't Hoff-Wislicenus theory as to the position of atoms in space is rendered necessary; but if the two are polymers, one having a molecular weight n times that of the other, then the theory in its present form will still hold. Hence it was imperative to determine without doubt the molecular weight of some two typical isomers. But the compounds in question are not volatile, so that vapor density determinations were out of the question. In this difficulty Prof. Meyer has tested the discovery of M. Raoult upon a number of compounds of known molecular weights, and found it perfectly reliable and easy of application. The method depends upon the lowering of the solidifying point of a solvent, such as water, benzine, or glacial acetic acid, by the introduction of a given weight of the substance whose molecular weight is to be determined. The amount by which the solidifying point is lowered is connected with the molecular weight, M, by the following extremely simple formula: M = T x (P / C); where C represents the amount by which the point of congelation is lowered, P the weight of anhydrous substance dissolved in 100 grammes of the solvent, and T a constant for the same solvent readily determined from volatile substances whose molecular weights are well known. On applying this law to the case of two isomeric benzil derivatives, the molecular weights were found, as expected, to be identical, and not multiples; hence Prof. Meyer is perfectly justified in introducing the necessary modification in the "position in space" theory. Now that this generalization of Raoult is placed upon a secure basis, it takes its well merited rank along with that of Dulong and Petit as a most valuable means of checking molecular weights, especially in determining which of two or more possible values expresses the truth.--_Nature._

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[Continued from SUPPLEMENT, No. 642, page 10258.]

THE DIRECT OPTICAL PROJECTION OF ELECTRO-DYNAMIC LINES OF FORCE AND OTHER ELECTRO-DYNAMIC PHENOMENA.[1]

[Footnote 1: An expansion of two papers read before the A.A.A.S. at the Ann Arbor meeting.]

By Prof. J.W. MOORE.

II. LOOPS.

If the wire, with its lines of force, be bent into the form of a vertical circle 1-1/8 in. in diameter, and fixed in a glass plate, some of the lines of force will be seen parallel to the axis of the circle. If the loop is horizontal, the lines become points.

FIELDS OF LOOPS AND MAGNETS.

Place now a vertical loop opposite to the pole of a short bar magnet cemented to the glass plate with the N pole facing it. If the current passes in one direction the field will be as represented by Fig. 14b; if it is reversed by the commutator, Fig. 14c is an image of the spectrum. Applying Faraday's second principle, it appears that attraction results in the first case, and repulsion in the second. The usual method of stating the fact is, that if you face the loop and the current circulates from left over to right, the N end of the needle will be drawn into the loop.

It thus becomes evident that the loop is equivalent to a flat steel plate, one surface of which is N and the other S. Facing the loop if the current is right handed, the S side is toward you.

TO SHOW THE ACTUAL ATTRACTION AND REPULSION OF A MAGNET BY A "MAGNETIC SHELL."

Produce the field as before (Fig. 14), carry a suspended magnetic needle over the field. It will tend to place itself parallel to the lines of force, with the N pole in such a position that, if the current passes clockwise as you look upon the plane of the loop, it will be drawn into the loop. Reversing the position of the needle or of current will show repulsion.

Clerk Maxwell's method of stating the fact is that "every portion of the circuit is acted on by a force urging it across the lines of magnetic induction, so as to include a greater number of these lines within the embrace of the circuit."[2]

[Footnote 2: Electricity and Magnetism, Maxwell, p. 137, §§ 489, 490.]

If the horizontal loop is used (Fig. 14a), the needle tries to assume a vertical position, with the N or S end down, according to the direction of the current.

If it is desired to show that if the magnet is fixed and the loop free, the loop will be attracted or repelled, a special support is needed.

A strip (Fig. 15) of brass, J, having two iron mercury cups, K_{1} K_{2}, screwed near the ends, one insulated from the strip, is fastened upon the horizontal arm of the ring support, Fig. 9, already described. The cups may be given a slight vertical motion for accurate adjustment. Small conductors (Figs. 16, 17, 18), which are circles, rectangles, solenoids, etc., may be suspended from the top of the plate by unspun silk, with the ends dipping into the mercury. The apparatus is therefore an Ampere's stand, with the weight of the movable circuit supported by silk and with means of adjusting the contacts. The rectangles or circles are about two inches in their extreme dimension. Horizontal and vertical astatic system are also used--Figs. 18, 18a. The apparatus may be used with either the horizontal or vertical lantern.

If the rectangle or circle is suspended and a magnet brought near it when the current passes, the loop will be attracted or repelled, as the law requires. The experiments usually performed with De la Rive's floating battery may be exhibited.

The great similarity between the loop and the magnet may be shown by comparing the fields above (Figs. 14b, 14c) with the actual fields of two bar magnets, Figs. 19, 19a.

It will be noticed that the lines in Fig. 19, where unlike poles are opposite, are gathered together as in Fig. 14b,--where the N end of the magnet faces the S side of the magnetic shell; and that in 19a, where two norths face, the line of repulsion has the same general character as in 14c, in which the N end of the magnet faces the N side of the shell.

Instead of placing the magnet perpendicular to the plane of the loop, it may be placed parallel to its plane. Fig. 14d shows the magnet and loop both vertical.

The field shows that the magnet will be rotated, and will finally take for stable equilibrium an axial position, with the N end pointing as determined by the rule already given.

If two loops are placed with their axes in the same straight line as follows, Figs. 14f, 14g, a reproduction of Figs. 14b and 14c will become evident.

It is obvious from these spectra that the two loops attract or repel each other according to the direction of the current, which fact may be shown by bringing a loop near to another loop suspended from the ring stand, Fig. 9, or by using the ordinary apparatus for that purpose--De la Rive's battery and Ampere's stand.

If two loops are placed in the same vertical plane, as in Figs. 14h and 14i, there will be attraction or repulsion, according to the direction of the adjacent currents. The fields become the same as Figs. 8 and 8a, as may be seen by comparing them with those figures.

Having thus demonstrated the practical identity of a loop and a magnet, we proceed to examine the effects produced by loops on straight wires.

If the loop is placed with a straight wire in its plane along one edge, there will be attraction or repulsion, according to the direction of the two currents, Figs. 20 and 20a, which are obviously the same as Figs. 8 and 8a.

If the wire is placed parallel to the plane of the loop and to one side, Figs. 20b and 20c, there will be rotation (same as Figs. 4b and 4c).

If the loop is horizontal and the wire vertical and on one side, the Figs. 20d, 20e are the same as 4d and 4e.

If the loop is horizontal and the wire vertical and axial, 20f and 20g, there will be rotation, and the figures are mere duplicates of 4g and 4h.

Fig. 20h shows a view of 20f when the wire is horizontal and the plane of the loop vertical. It is like 4i.

To verify these facts, suspend a loop from Ampere's stand, Fig. 9, and bring a straight wire near.

A small rectangle or circle may be hung in a similar manner. When the circuit is closed, it tends to place itself with its axis in a N and S direction through the earth's influence. The supposition of an E and W horizontal earth current will explain this action.

To exemplify rotation of a vertical wire by a horizontal loop, Fig. 21 may be shown.

A circular copper vessel with a glass bottom (Fig. 21) has wound around its rim several turns of insulated wire. In the center of the vessel is a metallic upright upon the top of which is balanced in a mercury cup a light copper [inverted U] shaped strip. The ends of the inverted U dip into the dilute sulphuric acid contained in the circular vessel.

The current passes from, the battery, up the pillar, down the legs of the U to the liquid, thence through the insulated wire back to the battery.

This is the usual form of apparatus, modified in size for the vertical or horizontal lantern.

(_To be continued._)

* * * * *

POISONS.

"Poisons and poisoning" was the subject of a discourse a few days ago at the Royal Institution. The lecturer, Professor Meymott Tidy, began by directing attention to the derivation of the word "toxicology," the science of poisons. The Greek word [Greek: toxon] signified primarily that specially oriental weapon which we call a bow, but the word in the earliest authors included in its meaning the arrow shot from the bow. Dioscorides in the first century A.D. uses the word [Greek: to toxikon] to signify the poison to smear arrows with. Thus, by giving an enlarged sense to the word--for words ever strive to keep pace, if possible, with scientific progress, we get our modern and significant expression toxicology as the science of poisons and of poisoning. A certain grim historical interest gathers around the story of poisons.

It is a history worth studying, for poisons have played their part in history. The "subtil serpent" taught men the power of a poisoned fang. Poison was in the first instance a simple instrument of open warfare. Thus, our savage ancestors tipped their arrows with the snake poison in order to render them more deadly. The use of vegetable extracts for this purpose belongs to a later period. The suggestion is not unreasonable that if war chemists with their powders, their gun cotton, and their explosives had not been invented, warlike nations would have turned for their _instrumenta belli_ to toxicologists and their poisons. At any rate, the toxicologists may claim that the very cradle of science was rocked in the laboratory of the toxicological worker. Early in the history of arrow tipping the admixture of blood with the snake poison became a common practice. Even the use of animal fluids alone is recorded--e.g., the arrows of Hercules, which were dipped in the gall of the Lernæan hydra. Hercules himself at last fell a victim to the blood stained tunic of the dead Centaur Nessus. As late as the middle of the last century Blumenbach persuaded one of his class to drink 7 oz. of warm bullock's blood in order to disprove the then popular notion that even fresh blood was a poison. The young man who consented to drink the blood did not die a martyr to science.

The first important question we have to answer is, What do we mean by a poison? The law has not defined a poison, although it requires at times a definition. The popular definition of a poison is "a drug which destroys life rapidly when taken in small quantity." The terms "small quantity" as regards amount, and "rapidly" as regards time, are as indefinite as Hodge's "piece of chalk" as regards size. The professor defined a poison as "any substance which otherwise than by the agency of heat or electricity is capable of destroying life, either by chemical action on the tissues of the living body or by physiological action by absorption into the living system." This definition excepted from the list of poisons all agencies that destroyed life by a simple mechanical action, thus drawing a distinction between a "poison" and a "destructive thing." It explains why nitrogen is not a poison and why carbonic acid is, although neither can support life. This point the lecturer illustrated. A poison must be capable of destroying life. It was nonsense to talk of a "deadly poison." If a body be a poison, it is deadly; if it be not deadly, it is not a poison. Three illustrations of the chemical actions of poisons were selected. The first was sulphuric acid. Here the molecular death of the part to which the acid was applied was due to the tendency of sulphuric acid to combine with water. The stomach became charred. The molecular death of certain tissues destroyed the general functional rhythmicity of the system until the disturbance became general, somatic death (that is, the death of the entire body) resulting. The second illustration was poisoning by carbonic oxide. The professor gave an illustrated description of the origin and properties of the coloring matter of the blood, known as _hæmoglobin_, drawing attention to its remarkable formation by a higher synthetical act from the albumenoids in the animal body, and to the circumstance that, contrary to general rule, both its oxidation and reduction may be easily effected. It was explained that on this rhythmic action of oxidizing and reducing _hæmoglobin_ life depended.

Carbonic oxide, like oxygen, combined with _hæmoglobin_, produced a comparatively stable compound; at any rate, a compound so stable that it ceased to be the efficient oxygen carrier of normal _hæmoglobin_. This interference with the ordinary action of _hæmoglobin_ constituted poisoning by carbonic oxide. In connection with this subject the lecturer referred to the use of the spectroscope as an analytical agent, and showed the audience the spectrum of blood extracted from the hat of the late Mr. Briggs (for the murder of whom Muller was executed), and this was the first case in which the spectroscopic appearances of blood formed the subject matter of evidence. The third illustration of poisoning was poisoning by strychnine. Here again the power of the drug for undergoing oxidation was illustrated. It was noted that although our knowledge of the precise _modus operandi_ of the poison was imperfect, nevertheless that the coincidence of the first fit in the animal after its exhibition with the formation of reduced _hæmoglobin_ in the body was important.

There followed upon this view of the chemical action of poison in the living body this question: Given a knowledge of certain properties of the elements--for example, their atomic weights, their relative position according to the periodic law, their spectroscopic character, and so forth--or given a knowledge of the molecular constitution, together with the general physical and chemical properties of compounds--in other words, given such knowledge of the element or compound as may be learned in a laboratory--does such knowledge afford us any clew whereby to predicate the probable action of the element or of the compound respectively on the living body? The researches of Blake, Rabuteau, Richet, Bouchardat, Fraser, and Crum-Brown were discussed, the results of their observations being that at present we were unable to determine toxicity or physiological action by any general chemical or physical researches. The lecturer pointed out that such relationship was scarcely to be expected. Poisons acted on different tissues, while even the same poison, according to the dose administered and other conditions, expended its toxic activity in different ways.

Further, the allotropic modifications of elements and the isomerism of compounds increased the difficulties. Why should yellow phosphorus be an active poison and red phosphorus be inert? Why should piperine be the poison of all poisons to keep you awake, and morphine the poison of all poisons to send you asleep, although to the chemist these two bodies were of identical composition? The lecturer urged that the science of medicine (for the poisons of the toxicologist were the medicines of the physician) must be experimental. Guard jealously against all wanton cruelty to animals; but to deprive the higher creation of life and health lest one of the lower creatures should suffer was the very refinement of cruelty. "Are ye not of much more value then they?" spoke a still small voice amid the noisy babble of well intentioned enthusiasts.--_London Times._

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ARTIFICIAL MOTHER FOR INFANTS.

All the journals have recently narrated the curious story of the triplets that were born prematurely at the clinic of Assas Street. Placed at their birth in an apparatus constructed on the principle of an incubator, in order to finish their development therein, these frail beings are doing wonderfully well, thanks to the assiduous care bestowed upon them, and are even showing, it appears, a true emulation to become persons of importance.

Every one now knows the incubator or "artificial hen"--that box with a glass top in which, under the influence of a mild heat, hens' eggs, laid upon wire cloth, hatch of themselves in a few days, and allow pretty little chicks to make their way out of the cracked shell.

This ingenious apparatus, which has been adopted by most breeders, gives so good results that it has already supplanted the mother hens in all large poultry yards, and at present, thanks to it, large numbers of eggs that formerly ended in omelets are now changing into chickens.

Although not belonging to the same race, a number of children at their birth are none the less delicate than these little chicks.

There are some that are so puny and frail among the many brought into the world by the anæmic and jaded women of the present generation that, in the first days of their existence, their blood, incapable of warming them, threatens at every instant to congeal in their veins. There are some which, born prematurely, are so incapable of taking nourishment of themselves, of breathing and of moving, that they would be fatally condemned to death were not haste made to take up their development where nature left it, in order to carry it on and finish it. In such a case it is not, as might be supposed, to the exceptionally devoted care of the mother that the safety of these delicate existences is confided. As the sitting hen often interferes with the hatching of her eggs by too much solicitude, so the most loving and attentive mother, in this case, would certainly prove more prejudicial than useful to her nursling. So, for this difficult task that she cannot perform, there is advantageously substituted for her what is known as an artificial mother. This apparatus, which is identical with the one employed for the incubation of chickens, consists of a large square box, supporting, upon a double bottom, a series of bowls of warm water. Above these vessels, which are renewed as soon as the temperature lowers, is arranged a basket filled with cotton, and in this is laid, as in a nest, the weak creature which could not exist in the open air.

Through the glass in the cover, the mother has every opportunity of watching the growth of her new born babe; but this is all that she is allowed to do. The feeding of the infant, which is regulated by the physician at regular hours, is effected by means of a special rubber apparatus, through the aid of an intelligent woman who has sole charge of this essential operation. The aeration of the little being, which is no less important, is assured by a free circulation, in the box, of pure warm air, which is kept at a definite temperature and is constantly renewed through a draught flue. The least variations in the temperature are easily seen through a horizontal thermometer placed beneath the glass.

Thus protected against all those bad influences that are often so fatal at the inception of life, even to the healthiest babes, preserved from an excess or insufficiency of food, sheltered from cold and dampness, protected against clumsy handling and against pernicious microbes, sickly or prematurely born babies soon acquire enough strength in the apparatus to be able, finally, like others, to face the various perils that await us from the cradle.

The results that have been obtained for some time back at Paris, where the surroundings are so unfavorable, no longer leave any doubt as to the excellence of the process. At the lying-in clinic of Assas Street, Doctors Farnier, Chantreuil, and Budin succeeded in a few days in bringing some infants born at six months (genuine human dolls, weighing scarcely more than from 2¼ to 4½ pounds) up to the normal weight of 7½ pounds.--_L'Illustration._

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GASTROSTOMY.

Surgery has, as is well known, made great progress in recent years. Apropos of this subject, we shall describe to our readers an operation that was recently performed by one of our most skillful surgeons, Dr. Terrillon, under peculiar circumstances, in which success is quite rare. The subject was a man whose oesophagus was obstructed, and who could no longer swallow any food, or drink the least quantity of liquid, and to whom death was imminent. Dr. Terrillon made an incision in the patient's stomach, and, through a tube, enabled him to take nourishment and regain his strength. We borrow a few details concerning the operation from a note presented by the doctor at one of the last meetings of the Academy of Medicine.

Mr. X., fifty-three years of age, is a strong man of arthritic temperament. He has suffered for several years with violent gastralgia and obstinate dyspepsia, for which he has long used morphine. The oesophagal symptoms appear to date back to the month of September, 1887, when he had a painful regurgitation of a certain quantity of meat that he had swallowed somewhat rapidly.