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FEEBLY SUSCEPTIBLE SUBSTANCES]
349
MAGNETISM

obtained by Fleming and Dewar to suggest the probability that

Bismuth.-Bismuth is of special interest, as being the most strongly diamagnetic substance known, the mean value of the best determinations of its susceptibility being about -14><10'° (see G. Meslin, C. R., 1905, 140, 449). The magnetic properties of the metal at different temperatures and in fields up to I5SO 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, 27 3° C. His results appear to show the relation -KX106=I'38I-O'OO1551°.

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 tc= -13-23><10'“ As the temperature was raised up to 273°, rc gradually fell to-9-38><10'6, rising suddenly when fusion occurred to -0-37><1o"', at which value it remained constant when the fluid metal was further heated. Fleming and Dewar give for the susceptibility the values-13-7X1o'° at 15° C. and -15-9X10'° at ”182°, the latter being approximately equivalent to K><1o'= *I'62. Putting t°=-182 in the equation given above for Curie's results, we get KX 106=-1-66, a value sufficiently near that the diamagnetic susceptibility varies inversely as the temperature between-182° and the melting-point. Other Diamagnetics -The following table gives Curie's determinations (Jonrn. de Phys., 1895, 4, 204) of the specific susceptibility K of other diamagnetic substances at different temperatures. It should be noted that K=/c/density. Fe(1) is iron contained in F eCl2 and Fe(2) iron contained in FC2(NO3)5

Curie has shown, for many paramagnetic bodies, that the specific susceptibility K is inversely proportional to the absolute temperature 0. Du Bois believes this to be an important general law, applicable to the case of every paramagnetic substance, and suggests that the product K0 should be known as “ Curie's constant ” for the substance., Elementary Bodies and Atomic Susceptibility.-Among a large number of substances the susceptibilities of which have been determined by ]. Koenigsberger (Wied Ann., 1898, 66, 698) are the following elements:-

Element. x X 105. Element. K X 106. Copper. -0'82 Tellurium - 2'10

Silver . -I'5I Graphite + 2

Gold -3°07 Aluminium + I'80

Zinc . -O'96 Platinum +22

Tin +0'46 Palladium. +50 to 60

Lead ' -I'IO Tungsten +14

Thallium . -4'61 Magnesium + 4

Sulphur -o'86 Sodium + 2'2

Selenium (red) . -0'50 Potassium. + 3'6 In a table accompanying K0enigsberger's paper the elements Substance. Temp. °C. -K><1o°.

Water ..... 15 189 0°790

Rock salt ... 16 455 o'580

Potassium chloride .... 18 465 0'55O sulphate ... . 17 460 0'430

nitrate (fusion 350°) 18 420 0'330 Quartz .. 18 430 0°441

ulphur, solid or fused 18 225 0'5I0 Selenium, solid or fused 20 200 0'320 fused 240 415 0'307

Tellurium . . 20 305 O'3II

Bromine ... . 20 0'4IO

Iodine, solid or fused 18 164 o'385 Phosphorus, solid or fused IQ 71 O'92O amorphous . 20 275 0730

Antimony, electrolytic ' 20 0'680 540 o'470

Bismuth, solid 20 I' '§ 5O

273 o'957

fused . . . 273 405 o'o38

For all diamagnetic substances, except antimony and bismuth, the value of K was found to be independent of the temperature. Paramagnetic Substances.-Experiments by ] S. Townsend (Phil. Trans., 1896, 187, 533) show that the susceptibility of solutions of salts of iron is independent of the magnetizing force, and depends only on the quantity of iron contained in unit volume of the liquid. If W is the weight of iron present per c.c at about 10° C., then for ferric salts 10°»< = 266W -o'77

and for ferrous salts

IO5K=2O6W-O'77,

the quantity -0-77 arising from the diamagnetism of the water of solution. Annexed are values of IOGK for the different salts examined, w being the weight of the salt per c.c of the solution. Salt. 1o°»<+o'77 Salt. 1o°t<+o°77

F@2Cls . . QI '6'w FeCl2 90'8w Fe2(SO4)3 . 74'5'w FeSO4 .. 74'9'LU FC2<NO3)6 . . 6I'5'w

Susceptibility was found to diminish greatly with rise of temperature. According to G. lager and S. Meyer (Wien. Akad Sitz, 1897, 106, II a, p. 623, and 1898, 107, II.a, p. 5) the atomic susceptibilities k of the metals nickel, chromium, iron, cobalt and manganese in solutions of their salts are as follows:- Metal k X 106. Metal. kX 106.

Ni 4'95=2'5><2 C0 IO'0=2'5X4

Cr 6'25=2'5><2'5 Fe(2) 12'5=2'5X5 Fe(1) 7'5 =2'5X3 Mn. 15'0=2'5><6 are arranged upon the periodic system and the atomic susceptibility (product of specific susceptibility into atomic weight) is given for each. It appears that the elements at about the middle of each row are the most strongly paramagnetic; towards the ends of a row the susceptibility decreases, and ultimately becomes negative. Thus a relation between susceptibility and atomic weight is clearly indicated. Tables similarly arranged, but much more complete, have been published by S. Meyer (Wied. Ann., 1899, 68, 325 and 1899, 69, 236), whose researches have filled up many previously existing gaps. The values assigned to the atomic susceptibilities of most of the known elements are appended. According to the notation adopted by Meyer the atomic susceptibility k=/<>< at0mic-weight/ (density X 1000). Meyer thinks that the susceptibilities of the metals praseodymium, neodymium, ytterbium, samarium, gadolinium, and erbium, when obtained in a pure form, will be found to equal or even exceed those of the well-known ferromagnetic metals. Many of their compounds are very strongly magnetic erbium, for example, in Er2O3 being four times as strong as iron in the familiar magnetite or lodestone, Fe2O3. The susceptibilities of some hundreds of inorganic compounds have also been determined by the same investigator (loc. cit) Among other researches relating to atomic and molecular magnetism are those of O. Liebknecht and A. P. Wills (Ann. d. Phys., 1900, 1, 178), H. du Bois and O. Liebknecht (ibid. p. 189), and Meyer (ibid. p. 668). An excellent summary regarding the magnetic properties of matter, with many tables and references, has been compiled by du Bois (Report to the Congrés Int. de Phys., Paris, 1900, ii. 460).

v

Element 105k Element 106k Element 105k Be +072 Cu -0'o06 Cs - 0'03

B +o'o5 Zn -O'OIO Ba - O'O21

C -o'05 Ga - La +13'o

N? Ge - Ce +34'O

0 + As P Pr + U,

F '-0'OI1 Se -O'025 Nd + g

-o'033 Sa + 3;

Na -o'oo51 .. . .. . . G d + <0 Mg +0'014 Rb -O'O21 .... .

Al + Sr -O'O21 Er +41 '8(?).

Si +0'OO2 Y +3'2(?) .. . .. .. . P -o'o07 Zr -O'0I4 Yb -i- (P)

S -0'OII Nb +o'49(?) Ta + 1'02 (?) Cl ""O'O21 Mo +O'O24 W. + O°I

+ Os +0'074

K -o'0011 Rh + Ir +

Ca -o'003' Pd +o°55 Pt + 0'227

Sc? Ag -O'OI6 Au - O'O3I

Ti +o'09 Cd -O'OI5 Hg - o'030

V +O'I7 In -O'OI1 Tl - o'93

Cr + Sn +o'0041 Pb - 0'025

Mn + an Sb -0'069 Bi - 0'023

Fe + 0 Te -o'o39 .. . . .

Co + B I -o'040 Th +16'0(?)

Ni -}- U' ..... ... . . .. U + 0'2I 1 Calculated.