The influence of traction in diminishing the susceptibility of nickel was first noticed by Kelvin (W.
The requirements of barley within the soil, and its susceptibility to the external influences of season, are very similar to those of its near ally, wheat.
The magnetic susceptibility expresses the numerical relation of the magnetization to the magnetizing force.
Villari in 1868 that the magnetic susceptibility of an iron wire was increased by stretching when the magnetization was below a certain value, but diminished when that value was exceeded; this phenomenon has been termed by Lord Kelvin, who discovered it independently, the " Villari reversal," the value of the magnetization for which stretching by a given load produces no effect being known as the " Villari critical point " for that load.
Those substances which are attracted, or rather which tend, like iron, to move from weaker to stronger parts of the magnetic field, are termed paramagnetic; those which are repelled, or tend to move from stronger to weaker parts of the field, are termed diamagnetic. Between the ferromagnetics and the paramagnetics there is an enormous gap. The maximum magnetic susceptibility of iron is half a million times greater than that of liquid oxygen, one of the strongest paramagnetic substances known.
Bismuth, the strongest of the diamagnetics, has a negative susceptibility which is numerically 20 times less than that of liquid oxygen.
From the equation K=(µ - I)/47r, it follows that the magnetic susceptibility of a vacuum (where µ = I) is o, that of a diamagnetic substance (where, u < I) has a negative value, while the susceptibility of paramagnetic and ferromagnetic substances (for which µ> I) is positive.
A substance of which the real susceptibility is will, when surrounded by a medium having the susceptibility k', behave towards a magnet as if its susceptibility were - -}-4,rK').
Since i +47-K' can never be negative, the apparent susceptibility will be positive or negative according as is greater or less than Thus, for example, a tube containing a weak solution of an iron salt will appear to be diamagnetic if it is immersed in a stronger solution of iron, though in air it is paramagnetic.4 Circular Magnetization.
The body (or each element of it) will tend to set itself with its axis of greatest susceptibility parallel to the lines of force, while, if the field is not uniform, each volume-element will also tend to move towards places of greater or smaller force (according as the substance is paramagnetic or diamagnetic), the tendency being a maximum when the axis of greatest susceptibility is parallel to the field, and a minimum when it is perpendicular to it.
Curves of Permeability and Susceptibility.-The relations of µ (= B/H) to B, and of to I may be instructively exhibited by means of curves, a method first employed by H.
Below is given a selection from Bidwell's tables, showing corresponding values of magnetizing force, weight supported, magnetization, induction, susceptibility and permeability: - A few months later R.
Ann., 1880, 11, 399) that in weak fields the relation of the magnetization I to the magnetizing force H is approximately expressed by an equation of the form I =aH +bH2, or K=I/H =a+bH, whence it appears that within the limits of Baur's experiments the magnetization curve is a parabola, and the susceptibility curve an inclined straight line, x being therefore a known function of H.
While therefore the initial susceptibility of nickel is less than that of iron and steel, the range of magnetic force within which it is approximately constant is about one hundred times greater.
4 Nagaoka' has described the remarkable influence of combined torsion and 'tension upon the magnetic susceptibility of nickel, and has made the extraordinary observation that, under certain conditions of stress, the magnetization of a nickel wire may have a direction opposite to that of the magnetizing force.
- It has long been known that iron, when raised to a certain " critical temperature " corresponding to dull red heat, loses its susceptibility and becomes magnetically indifferent, or, more accurately, is transformed from a ferromagnetic into a paramagnetic body.
But if the alloy is heated up to 580° C. it loses its susceptibility - rather suddenly when H is weak, more gradually when H is strong - and remains non-magnetizable till it is once more cooled down below the freezing-point.
Guillaume' the temperature at which the magnetic susceptibility of nickel-steel is recovered is lowered by the presence of chromium; a certain alloy containing chromium was not rendered magnetic even by immersion in liquid air.
Heusler 2 in 1903 that certain alloys of the non-magnetic metal manganese with other non-magnetic substances were strongly magnetizable, their susceptibility being in some cases equal to that of cast iron.
Manganese, though belonging (with chromium) to the iron group of metals, is commonly classed as a paramagnetic, its susceptibility being very small in comparison with that of the recognized ferromagnetics; but it is remarkable that its atomic susceptibility in solutions of its salts is even greater than that of iron.
Owing to the difficulty of determining the magnetization I and the susceptibility K with accuracy, it has not yet been possible to submit this formula to a quantitative test, but it is said to afford an indication of the results given by actual experiment.
- The following are recent determinations of the magnetic susceptibility of water: Observer.
Important experiments on the susceptibility of oxygen at different pressures and temperatures were carried out by P. Curie (C.R.
He found that the susceptibility for unit of mass,.K, was independent of both pressure and magnetizing force, but varied inversely as the absolute temperature,.
Pressure is 0'00141 grm., the mass at any absolute temperature 0 is by Charles's law o oo 141 X 2 739 = 0 3 849/9 grm.; hence the susceptibility per unit of volume at 760 mm.
For air Curie calculated that the susceptibility per unit mass was Io 6 K= 7830/0; or, taking the mass of 1 c.c. of air at o° C. and 760 mm.
If V is the volume of a ball, H the strength of the field at its centre, and re its apparent susceptibility, the force in the direction x is f= K'VH X dH/dx; and if K',, and are the apparent susceptibilities of the same ball in air and in liquid oxygen, K' Q -K'o is equal to the difference between the susceptibilities of the two media.
The susceptibility of air being known - practically it was negligible in these experiments - that of liquid oxygen can at once be found.
A small but decided tendency to a decrease of susceptibility in very strong fields was observed.
It appears, therefore, that liquid oxygen is by far the most strongly paramagnetic liquid known, its susceptibility being more than four times greater than that of a saturated solution of ferric chloride.
On the other hand, its susceptibility is about fifty times less than that of Hadfield's 12% manganese steel, which is commonly spoken of as non-magnetizable.
Further acquaintance makes us feel a unity of character underlying this susceptibility to the impressions of the moment.
16 Some atoning virtue seems also attributed to the Resurrection;' ` ' Christ's sayings connect admission to the kingdom of God with susceptibility to the influence of His personality, faith in Himself and His mission, and the loyalty that springs from faith.
The Sabellian races of central and eastern Italy and the Italo-Celtic and Venetian races of the north, in whom the poetic susceptibility of Italy was most manifest two generations later, were not, until after the Social war, sufficiently in sympathy with Rome, and were probably not as yet sufficiently educated to induce them to contribute their share to the national literature.
Exquisite as was already his susceptibility to beauty and his mastership of the rarest poetic material, we cannot doubt that Chenier was preparing for still higher flights of lyric passion and poetic intensity.
Closely related to the structure of metals is their degree of "plasticity" (susceptibility of being constrained into new forms without breach of continuity).
On the other hand, inheritance was dismissed, or survived only as a "susceptibility," in the cases of tubercle, leprosy and some other maladies now recognized as infectious; while in others, as in syphilis, it was seen to consist in a translation of the infectious element from parent to offspring.
Thus the field of disease arising not from essential defect in the body, but from external contingencies, is vastly enlarging; while on the other hand the great variability of individuals in susceptibility explains the very variable results of such extrinsic causes.
Ewing has also examined the effects produced by longitudinal compression upon the susceptibility and retentiveness of nickel, and found, as was to be expected, that both were greatly increased by pressure.
The magnetic properties of the metal at different temperatures and in fields up to 1350 units have been studied by P. Curie (loc. cit.), who found that its " specific susceptibility " (K) was independent of the strength of the field, but decreased with rise of temperature up to the melting-point, 273° C. His results appear to show the relation - K X10 6 = I'381 - O'o0155t°.
Assuming the density of Bi to be 9.8, and neglecting corrections for heat dilatation, his value for the susceptibility at 20° C. is equivalent to - 13.23 X 10 -6.
Fleming and Dewar give for the susceptibility the values-13.7 X 6 at 15° C. and - 15.9X 10 -6 at - 182°, the latter being approximately equivalent to KX Io 6 = - 1.62.