Further experiments with liquid helium. R. On the electric ... · 133d ~ 13tÏ we repol'ted Ihat "Kahlbaum" lead became supel'conducting at the boiling poinl of liquid helium, and

PhYBicB. - "Furthe1' expe1'iments with liquid helium. R. On the electric resistance of pure metals etc. XI. Measw'ements con-cerninp t!te elect"ic 1"esi~tance of 01'dina1'y lead and of umniurn lead below 14° K." (Comm. N° . 160b from the Physical Labo-ratOl'y at Leiden). By Prof. H, KAMRRJ.1NGH ONNES and W. TUYN,

(Communicated at the meeting of October 28, 1922.)

~ 1. Object of t!te 1·esem·ch. Met/wd of p"epflring the 1'esistances. In Comm. N°. 133d ~ 13tÏ we repol'ted Ihat "Kahlbaum" lead

became supel'conducting at the boiling poinl of liquid helium, and remained so al 4,°3 K., the highest lemperat.ure altainable with Ihe usual cl'yoslal for liquid helium j ill + 15 of the same Cornm. frorn Ihe thl'eshold value of the cUITenl at 4,°25 K. t.he vanishing point tempel"atul'e was eslimated at about 6° K. The object of the invest-igation descl'Ïbed below was to establish the vanishing point tempe-I'atlll'e of lead mOI'e accurately, as weil as 10 trace the difference ill the vallishing point temperatul'e of lead and ul'anium lead (Ra U) and to follow the course of the change in the resistance of lead with the temperatnre above the vanishing point, if possible up 10 14°,0 K, the lowest liqnid hydrogen tempel'atllre. Regarding a possible diffel'ellee of vanishing point lemperatlll'e for isotopes it seemed not impossible th at the OCClIlTence of the supel'conductivity might be illfluenced hy the mass of the nucleus. I).

FOI' the preparation of the reAistances we used "Kahlbaum" lead alld ul"allium lead (Ra G), of which Pl'of. HÖNIGSCHMID of Vienna ver)" kindly put 16,5 gl'. at our disposal j Ihe atomic weight of ordinal'Y lead from non-radio-active sources is 207,20, that of Ra G fl'om BRÖGGERIT \Ised is 206,06 '). Wil'es were drawn from ~oth kinds of lead Ilnd resistances prepared from them in the manner described in ~ 1 of Comm. Nt. 160fl j the chemical pl'operties of the metal

I) Concerning the properties of isotopes see the article by K. F AUNS in the Elster-Geilei-Festschrift (Vieweg) and the Presidential j\.ddress 10 the American Association at I3altimore, Dec. 1918 by T. W. RICHARDS.

,) According 10 alelIer from the firm of May 17th, 1916, "Kahlbaum" lead contains a trace of Cu and Fe, the tol al impurity is less than 0,01%; in a letter of Dec. 8th, 1916 they give a more precise calculation of impurity: 0,002% Cu and Fe. Fol' an account of the atomie weight of lead isotopes cf. ~'. W. ASTON "Isotopes", London 1922.

452

made it possible 10 extend less car'e on them than on the prepar'a-tion of the Tl-resistances, so that it is not necessal"y that the resistances should be shnt off from the air' in a glass lube witll helium gas. We used the l"esistan ces Pb-1919-B, diameter 0,5 m.m. not ell~losed in a helium atmosphel'e, Pb-1919·1, diameter' 0,12 m.m.

o o

G---l+\j.öw;;1lIIIr.;::;:;;w"" I

F

A

E

Th

B

enclosed in a helium atmosphere and lsotope Pb-1919-I, in dimensions as much as possible the same as Pb-1919-1 and tl"eated in the same wa.\'.

~ 2. An'an,qement of the C1·yostat. The cryostat wit.h which Ihe experiments wel"e made, is executed by and uIIder the supel"vision of tlle chief of the Techn. Dep. of tlre CI·yog. Lab., Mr' . G. J. FJ.IM. Ronghly speaking, it is the same as that desel'ibed in Comm . N°.124b. A charact-eristic of Ihe present cr'yostat is that objects to be measured are sUlTounded by helium vapour or gas (the lattel' at very low tempemtul"e) ; by using it, Ihe te mperature field bel ween the boiling point of helium (4°,2 K.) and Ihe lowest temp. obtainable with liquid hydl'ogen (J 4°,0 K.) is bridged ovel' for the Ihst ti me . For the arrangement see fig. 1 . In the enlirely silvered vacuunr glass A, an also entirely silvered vacuum glass B hangs in an in\'el"ted position, ending in a single silvel'ed glass tube; the bell-shaped space inside this glass is the ex-perimental chambel'. In Ihis space are found the resistances (in fig . 1 there is only one, marked W) and the heliumgas-thermometer Tit . The uppel' end of B opens out outside Ihe cl'yostat and is connected with the gasholder ; B is there pl'ovided with a regulating tap K for blowing off (not visible in the drawing). The liqnid helium comes in thl'Ough the enlrance D; the floatel' C shows the height of the helium level. If the tap K, leading to the gasholder, stands open, the helium will fill both A and B; at the beginning of the ex-pel'iment measurements can thlIs be made at the boilillg point of liquid helium . If tlle

453

tap K is closed, the heliullI vapoll!' fomled will quickly drive the liquid helium out of Ihe bell.shaped cl'Jostat space; byopening the tap K and pnlting 011 the elecll'ic heatillg in the spiral F, a constant vapour str'eam may be sent Ihrough Ihe eryoslat; the stream may be brought 10 Ihe lempenüure desÏl'ed by eleclric heating of the spil'al . G; lhus Ihe liquid level ·of the evapOl'ating helium remains betweell F and G, The coppel' mantie E inside the bell contributes 10 the acquiring of an even temperatul'e ovel' the whole space; further' experimenls must show in how far uniformity of temperature has been achieved wilh Ihe alTangemeIJt as descdbed , The tit'st cooling uses a great deal of liquid helium.

~ 3, Resistance and temperature dete1'minations,

The resislances are measnred by compal'ison of the defleetions of Ihe galvanometer, when eonnected with Ihe extremities ofan unkllowTl and a knowIl ,'esistance (0,001 or 0,01 !]. O. W OI,FF) ; the resistances are proportional to Ule menIIs of Ihe deflections for both directions of the ClllTent, as follows from tht'! comparison of the detleetions for 0,001 and 0,01!2.

The lempeJ'attu'es are deteJ'mined with a helinmgasthermometel' of cOllstant volume and wilh open mallometer, the height of the barometer is read fJ'om an aneroid. In the measnJ'ements of May 181h 1920 the zero pl'essUl'e of Ihe thel'mometer was calculated to be abont 1140 e.m.; as it was II0t easy lo detel'mine Ihis pressure accurately, the pl'essul'e at the temperature of Iiqnid helium was taken as calibratioll point (this temperature followed from the vapour pressUl'e of the bath).

For Ihe measul'ements of May 28th 1920 the zero-pressure of the thel'llIometel' wa!! decl'eased to 290 cm., in ordeJ' 10 have less difliculty with the cOI'l'ections on the provisional international Kelvin scale, these correetions. in and below the field of liquid hydrogen being insuflicienlly known, As two calibl'ation points the tensions of the thermometer sel'ved, plaeed in liquid heliullI (May 28th 1920) and in liqlJid hydl'ogen (May 29th 1920); the temperatlJl'es of these points again follow trom the vapouJ' pressUI'e of the bath, using the data from Comm. N°, 147b and N°. 156b.

For the cOl'l'ection of the inoications of the thermometer on the p,'ovisional internatiollal Kelvin scale, we had at OUl' disposal the data of Comm. Sllppl. N°, 34a, p. 17, nole 4 (obtained from the data of Comlll, N°. 102c), ill whieh B - 254o C. has been taken zero,

El SI> ..::: :: (> '" ..... 8 Er 11 .... ~ ""3 5- ;:.

41'1 (1) I ö 6"3 0- ~ () ~ ..-. e.a ,:3 g 0 3 E' g tJj ö' :;- Ö 8 ? -., 0 I 0" (1) ~ ~ (1) .a ::> ti., tJj (1) (1) 0 CJQ 00 ____ _ 00

1ll ~ I (; _.'-' ~ ti ""3 (1).... b5 < 0- '-l g (1) ~ I ~:;. 6"3 ;::: ~ I t:tI 0-" 0

(1) ____

= = ... (>

;-:::s S' ., 0

~ GO; .,

(1) 3 0-~'" ;:;. (1) - 0-:::s < !!!. 0 ~ 4ë" ;n ' a

(1) -(1)

Er < (1) g. ~ 3 ",- (1)

TABLE I.

B. (:,. t I)

Temp. (Pressure heliumtbermometer at 0°. C. = 1000 m.m.) .

Old observations. I New observations. Old observations. I New observations. 20°.5 K. - 0.00010 + 0.04s

19.1 0.00000 + 0.03g 4.29 - 0.00305 + 0.051 4.22 - 9 .00347 + 0.052 3 71 - 0.00420 +O.~

3.44 - 0.00538 + O.O~ -

~

~

Furlher we have made use of the newly ealeulated 6 fs, and from this we deduee table 11.

TABLE 11.

Fitting I. pooe = 1140 e.m. May 18, 1921). I Filling 11. Pooc = 290 e.m. May 28 and 29, 1920. Tvapour T He. Wlcor.

Pin loeal P Tvapour T He. Wlcor.

pin loeal p 6. t m.m. Hg. THe'

6t m.m. Hg. THe · teDlioD rected tenlioD rected

0 0 4.20 K. 0.60 3.60 151.8 42 . 18 20 .37 K. 0.13 20 .24 209.7 10.3,

4.22 K- 0 . 15 4.07 42.7 10.4& I - -

455

and also from Comm. N". 119 § 5b B 4P,29K. = - 0,000047 1); Table V of Comm. N". 156a gives a resumé of the corrections, calculated with the above data. In accOl'dance with note 1 and 3, p. 27, Comm. N°. 156a here BI = 0,000499, B lOO = 0,000476, tliHe = = 0,0036614 are takelI, and the inflllence of the C's is neglec.led ').

New determinations, 10 be puolished sho/'tly, of helilllIl isothe/'ms at T= 20°,5, 4°,2, 3 ~ ,7 and 3°,4 K. gave p.·ovisional new vallles fOl' B, which thel'efo/'e infer the int/'odllction of different corrections in the provisional intel'll. Kelvin-scale; they are lal'gel' than those in Table V, Comm. W. 156a and they do not come into line so weil with thos~ for higher tempel'atures. FOl' the sake of eompleteneRs we give a cornparison of these in Table 1. (cf. p. 387).

§ 4. Tempemtw'e of the vanishin,q point. 0" May 18th and 28 t1l 1920 all tlll'ee I'esistallces pl'o\'ed snpel'condlleting iJl liqllid helium and behaved, thel'efol'e, in !.he IIsual way. Aftel' this the cl'yostat was gl'adnally hrought to a higher tempe/'atnre by electric heating of the vapOI'ised helinm. At a certain moment the galvanometer moved qllickly over 35 c.m. on the scale alld the vanishing point was apparently reached; the suddenness of the deflection speaks weil fOl' the usefnlness of the c!'yostat if not too high demands are put IIpon it. A repetition of the heating (very gl'adnally) confirmed the first resnlt. While the temperatllre was kept constant the thermo-meter was read at the vanishing point. The results al'e given in Table lIL

TABLE 111.

Data. Filling. P ps therm om. in T He, uncorrecled L t. T. local m.m. Ht.

° May 18, 1920. I 263.6 6.25 0,58 6 .8 K. May 28, 1920. 11 13.9 a. 1.08 0.15 a.1.23

b. 1.13 0.15 b. 7.28

I) The B = -- 0,000047 is that derived according to pv = RT + B; the B's V

further mentioned in lhis number are those according to pv = RT ( 1 + !). in agreement with the change of notation mentioned in note 360 of Comm. SuppJ. N°. 23.

') These values for Bo, B lOo and /X I He must be retained 10 get the corrections on th~ pl'ovisional internat. Kelvin-scale. Measurements have shown that it would have been more correct to use Bo = 0,000513, B100 = 0,000492 and /Xi He = 0,0036613 (Comm. N0. 102b, Table land Com. NU. 156a, p. 22, no te 1); this would lead to a second provisional intern. Kelvin-scaJe (helium-Avogadl'o-scale) for which reason we retain the first B's. .

456

In filling Il a is calculaled by inlel'polation bet.ween calibl'ation points :,w°,24 and 4°,07 K" b by using only tbe calibralion point 20°,24 K , in Ihe same wa)" as in filling r only calibl'alion point 3°,60K, needed to be Ilsed ,

The agl'eemenl between the meaSlll'ements wilh filling land 11 is ,bad. If in filling 1I we calculate, with the presslil'e increase of 10,3B Olm . pel' degl'ee, the temperature of the helium on Ma)" 28tb • 1920, the calcuJation yields 4°,27 K, while the vapoUl· pJ'eSSlll'e gave 4°,22 K (tabie 11); this is in favonr of Ihe measurements on May 28th • IC we fUl'thel' take the lal'ge l::.t's in filling I into consideration, a detel'mination with filling I desel'ves less confidehce than one with filling 11. We take T vanishing point lead = 7°,2 K, although it is still desirabie to make a more accurate detel'mination,

~ 5. Cornparison oj' the vanishin,q point tempemtw'es of lead and uranium lead (Ra G) .

On May 18th , 1920 the cross-tlll'ead of the kathetometel' was adjusted 10 Ihe mercury menisclIs in the open tube of Ihe thermo-meter at the pressure belonging to the vanishing point temperature of Pb-1919-1 (the menisrus in the closed tube must of course always be kept on the same mark).

Aftel' a decI'ease of temperature lsotope Pb-1919-/ was insel'ted in the resistance circuit and Ihe tempel'atllre again I'aised. IC the gal vanometel' moved, because the resistance passed thl'ough Ihe vanishing point, the meniscus in the tuhe of Ihe Ihel'mometer passed the CI'OSS thread; this phenomenon was cel·lain up to 1 mOl. Hg: "Raltlbaum" lead, atomie weight 207,20 and uranium lead (Ra G), atomie weight 206,06 have the same vilni.~hi1(q point tempemt1t1'e witltin the aeeuraey ofl/.o degree. The same I'esllit was yielded by Pb~1'919-B; an influence of the smaller CUlTent densily in conseqllence of the largel' diameter could not be detected (Ihe stl'ength of the measul'ing CUlTent was always 7,8 m.A.).

~ 6. Resistances above the tempemtlt1'e of the vanishin,q point. The results of these measurements are given in fig. 2; the point

most to the I'ight, placed within a square, is the l'esult of a, mea-surement in liquid hydrogen. As vanishing point 7°,2 K was taken, To make Ihe curve join on properly 10 the one in the field of liquid hydrogen it must be trared as in Ihe diagram; th at is why COITes-ponden ce with the points marked is defective. The broken cl'osses have the following meaning: if the difference between the vanishing

457

point temperatnres found on May 18th and May 28th may he attributed entirely to b.t ha\'illg been taken too large on May 18th , all the other temperatUl'es must be I'ecalclilated, Ihis recalclIlation yields the crosses. Allhough this aPP"oximation is theoretically 1I0t qllite cOlTect, as T -- b.t and not T ought to rise at every temperatul'e in lhe same ratio, yet the results are in favour of the suggested assumptioll.

%0 ~-r----------~----------~--------~~-------'

QOl0'r-~--------r-------~--------~--~~~

0.OO51---+------+------b~"------___I>-----___l

~OOO~·-L~--------~----------L---------~~-------L fi5 7.0

• o 1+1 :.

9.0 110

Fig. 2.

Pb-1919-1, ! lsótope Pb-1919-I, 18 May 1920. Pb-1919-B,

Pb- 1919-B, 28 May 1920.

>< Redueed observations: § 6.

1.3.0 T