BRITISH CHEMICAL ABSTRACTS
A .-PU RE CHEMISTRY
M A Y , 1928.
G eneral, P h y sica l, and In organ ic C h em istry.
S p e c tr o m e te r o r m o n o c h r o m a to r w ith le n se s or m i r r o r s fo r u s e w ith one o r tw o p r is m s of glass, q u a r tz , ro c k s a lt, etc. C. Le is s (Z. Physik, 1928, 47, 137— 142).—A new form of constant-devi- ation spectrom eter is described which can be used according to requirem ents w ith one or two prisms of glass (for visible region), quartz (up to 4 |jt), or rock salt (up to 1G ¡j.)- The arrangem ent of mirrors (or lenses) and prisms is such th a t the prisms arc always used in the position of minimum deviation.
The instrum ent.is very com pact and simple of a d ju st
ment. J . W. Sm it h.
D ire ct-v isio n sp e c tro s c o p ic a p p a r a tu s a n d m o n o c h ro m a to r w ith tw o p r is m s a n d c o n s ta n t deviation. C. Le is s (Z. Physik, 1928, 47, 143—
140).—A direct-vision spectroscope is described which can be used w ith either one or two prisms. Mirrors are mounted in perm anent connexion w ith th e prisms, which can be adjusted together w ith one movem ent.
I t is so arranged th a t any line focussed on the cross- wires or on the emergence slit has passed through the prism with minimum deviation. J . W. Sm it h.
S p a rk p ro d u c e r a s a n a to m is e r of s a lt so lu tio n s fo r fla m e s p e c tr a a n d th e p h o to g ra p h y of th e ir s p a r k s p e c tr a . W. Hir s c h e l (Z. Physik, 1928, 47, 147— 150).—A m ethod is described whereby the atomising properties of the spark producer can be employed for m aintaining a continuous flame spectrum. A small am ount of the solution of a salt is placed in th e bottom of the spark producer and sparking m aintained while a stream of coal gas is passed through the apparatus and burnt in a Bunsen burner. Only a few mg. of a salt solution are required to produce a good spectrum photograph, so th a t the m ethod is particularly applicable to small quantities of material. Methods of obtaining visible and u ltra
violet spark spectra by the use of th e same apparatus are also described. ” . . J . W. Sm it h.
L u m in o s ity of fla m e s c o n ta in in g s o d iu m v a p o u r. G. L . Lo c h e r (Physical R ev., 1928, [ii],
31. 466—469).—Except for small concentrations of sodium vapour, the luminosity of a sodium flame is proportional to the square root of its thickness. The luminosity of a flame is independent of the distribu
tion in it of the em itting vapour.
A. A. El d r id g e. D o u b le t c o m p o n e n ts of H„ in th e a b s o rp tio n s p e c tr u m of h y d ro g e n . L. S. Or n s t eIn, F.
Ze r x ik e, and J . L. Suvek, jun. (Z. Physik, 1928, 47, 627—630).—I t is shown experim entally th a t the durations of the two final states of H a are approxim
GG
ately equal. I t is concluded th a t th e cause cannot be th e m etastability of th e lower states.
W. E. Do w n e y. R e la tio n b e tw e e n th e s p e c tr a l lin e s of h y d r o g e n a n d of io n is e d h e liu m , a n d th e m o v e m e n ts of th e e le c tro n s. A. M. Tit o v (Ann. In st. Polyt.
Oural, 1926, 5, 37—48).—M athem atical.
C. W. Gib b y. S tr u c tu r e of b a n d s p e c tr u m of h e liu m . IV.
W. E. Cu r t is (Proc. Roy. Soc., 1928, A, 118, 157—
169; cf. A., 1925, ii, 722).—Details are given of three new bands having th e same final electronic s ta te (2P) as the three previously investigated (loc.
cit.). Two of th e new bands are closely associated w ith th e neighbouring strong bands 6400 and 4546, th e weak bands being due to th e vibration transition 1—-> 1, w ith th e initial electronic levels 3S and 4S , whilst th e strong bands arise from th e vibrationless molecule. Tho th ird new band has an initial elec
tronic level of effective quantum num ber 2-96. The com bination result indicates th a t th e final s ta te is identical with th a t of th e -R'P-branches of 5730, i.e., 2Pa(0), b u t its electronic designation is uncer
tain. The term constants have been accurately cal
culated for th e new bands and for 6400, 4546, and 5730. The molecular constants are thence determ ined and then- relations discusscd. F u rth er support is afforded to Lenz’s suggestion th a t the structure of the helium molecule is related to th a t of the hydrogen molecule (Verh. Physikal. Ges., 1919, 21, 632). I t is probable th a t a satisfactory m ethod of distinguish
ing between the A - and ^ -ro ta tio n a l sub-states could be based on th e effects on them of increasing excit
ation, for the electronic term value becomes greater for A th an for B , an d th e m om ent of inertia for the A -state remains alm ost constant, w hilst th a t for the ii-sta tc shows a fairly rapid increase.
L. L. Bir c u m s h a w. D is trib u tio n of in te n s ity in th e b a n d s p e c tr u m of h e liu m : th e b a n d a t 4650. W. H . J . Ch il d s
(Proc. Roy. Soc., 1928, A, 118, 296—317).—A m ethod is described for m easuring th e in tensity distribution in th e helium band a t 4650 Â. (first of the m ain series).
The spectrum is photographed in the usual way, b u t each plate is calibrated by exposure (for the same tim e as was necessary for th e band spectrum) to a num ber of sources of known relative intensity. The densities of both the lines and calibration marks, obtained by means of a stepped aperture, are found, and from th e m easurem ents on the calibration marks a curve connecting light intensity w ith photographic density is drawn. This is then used to translate the 449
450 B R IT IS H CHEM ICA L ABSTRA C TS.----A .
densities of the band-line images into relative densities.
Chance errors are eliminated by the policy of obtaining several records by entirely different m ethods and taking weighted means. The observed values are compared w ith th e predicted energy distribution calculated by means of the sum m ation rule. Quan
titatively, th e agreem ent is not. good, although th e observed intensity curves are of the predicted type.
N otably th e prediction th a t the Q-branch a t its greatest should be twice as strong as th e maximum intensity of th e P -branch is not fulfilled, the ratio being more nearly 10 : 7. The observed distribution is adequately described by an expression of the form ie~E'kT, where i is a linear function of j ’. The effective tem perature of the source, estim ated by assuming the distribution of angular mom entum to be governed by the Boltzman factor, is much higher th an the tru e tem perature. A higher tem perature is obtained from the (^-branch th an from the P- or 22'b ran ch es. Exam ination of the Doppler w idth of th e band lines indicates, however, th a t the distribu tion of translational velocities among th e em itting molecules is th a t corresponding w ith the tru e tem p erature of the gas in the tube.
L. L. Bir c u m s h a w. E m is s io n s p e c tr u m of th e c h ro m o s p h e re . A.
Un s o l d (Z. Physik, 1928, 46, 782—787).—The in ten sity distribution in the spectral lines em itted by the chromosphere is discussed, and an expression is derived for this distribution which leads to values for H„ which showT a satisfactory agreem ent with
observation. R . W. Ltjnt.
C o n d itio n s of e m is s io n of fo rb id d e n lin e s.
A. S. Ed d in g t o n (Month. N ot. Roy. Astron. Soe., 1927, 8 8 , 134—138).—Possibilities are discussed to account for the brightness of forbidden lines in nebulae in comparison with ordinary lines. I t is suggested th a t th e stim ulating radiation m ust be so weak th a t the atom is unlikely to absorb a quantum during the full duration of the m etastable state. A sim ilar explanation w'ould hold if nebular light were due to ordinary tem perature collisions, bu t the la tte r is regarded as improbable. I t is shown to be unlikely th a t th e coronium spectrum can consist of forbidden
lines. J . W. Sm ith.
D e n sity n e c e s s a ry to p ro d u c e th e n e b u la r s p e c tr u m . D. H. Me n z e l (Nature, 1928, 121, 61S).—A criticism (cf. Elvey, this vol., 9S).
A. A. El d r id g e. A rc s p e c tr u m of c a rb o n . A. Fo w l e r and E. W. H. Se l w y n (Proc. Roy. Soc., 1928, A, 118, 34—51; cf. Merton and Johnson, A., 1923, ii, 446).—
Photographs of the spectrum of an oxide of carbon in helium, covering th e region 1250—2760 in the first order and 1250— 1380 A. in the second order, have been tak en with the vacuum grating spectrograph. The effect of adm ixture w ith helium is to emphasise the known lines of C i w ith respect to those of C n which appear w ith them , and to introduce additional lines, m any probably due to C I. Results similar to those of Rycle (this vol., 97), b u t excluding some of th e fainter lines, have been obtained with currents much smaller th an those used by him, and this method has been utilised to extend the observations as far as
10120 A. in the near infra-red. I t appears th a t all th e ordinary sources yield lines of C I which arise from com binations of th e deeper term s of th e spec
trum , and special m ethods become necessary only for th e excitation of lines due to combinations of term s representing higher energy levels. The term s of C I predicted by the H eisenberg-H und theory are similar to those of N i i and O ill. The deepest term is a triplet P 0, the value of w-hich is estim ated a t 91,017, corresponding w ith an ionisation potential of 11-2 volts. A close sim ilarity between the spectra of C i, N i i, and 0 m is to be expected, since th e three atoms are similarly constituted. Each has six external electrons, b u t the nuclear charges are different. A regular progression is clearly shown in m ost of the term values in passing from 0 h i to C I.
L. L. Bir c u m s h a w. I n te n s itie s in th e s p a r k s p e c tr u m of ox yg en.
W. R. v a n W ijk (Z. Physik, 1928, 47, 622—626).—
The extended sum m ation rule of Ornstein and Burger (A., 1927, 81) has been experim entally found to apply to th e spark spectrum of oxygen (O n).
W. E . Do w n e y. L in e s p e c tr u m of oxygen. C. Mi h u l (Ann.
Physique, 1928, [x], 9, 261—380).—428 lines of th e second order spectrum of oxygen, and 315 lines of the th ird order spectrum between 7000 and 2050 A. have
been classified. C. W. C ibby.
S p a r k s p e c tr u m of n eo n . II. T. L. d e Br u i n
(Z. Physik, 1928, 46, 856—872; cf. A., 1927, 910).—
The spark spectrum excited by dam ped wave-trains of unspecified frequency and voltage in neon a t 2 cm.
has been examined by a grating m ethod. A large num ber of lines have been recorded and classified.
R. W. Ltjnt. S p e c tr u m of io n is e d a r g o n (A i i). T. L. d e Br u in (Nature, 1928, 121, 576).—A considerable num ber of th e lines of A n have been classified, and a doublet and a quadruplet term system has been found. The term stru ctu re is analogous to th a t of F i and Ne i i. A. A. El d r id g e.
S p a r k s p e c tr u m of s ilv e r (Ag II). A, G.
Sh e n s t o n e (Physical Rev., 1928, [ii], 31, 317—322).
—Tabulated values are given of term s, intervals and lim its, and intensities in m ultiplets. The lines (3372-51— 1932-88 A.) are classified w ith th eir in ten sities, frequencies, and designations. The calculated ionisation potential is 17-1 volts from os*JDs.
A. A. El d r id g e. In te n s ity of fo rb id d e n m u ltip le ts . L. S. Or n s t e in and H. C. Bu r g e r (Naturwiss., 1927, 15, 670—671; Chem. Zentr., 1927, ii, 2263).—The sum m ation rule and intensity form ula for norm al m ulti
plets are valid for forbidden m ultiplets of th e cadmium arc spectrum . The relation p fjp d is approxim ately proportional to th e 0-4 power of th e pressure, and increases w ith increasing current. A t atm ospheric pressure p fjp d is 0-01 and 0-10 for th e first and second members respectively, the ratio 10 being characteristic for th e cadmium atom.
A. A. El d r id g e. M e r c u ry s p e c tr a . M . Po n t e (Compt. rend., 1928, 186, 633—635).—The special typ e of discharge produced a t a tungsten electrode in an intense high-
G E N E R A L , P H Y S IC A L , AN D IN O R G A N IC C H E M ISTR Y . 451
frequency field, using oscillations of very short wave
length (this vol., 212), has been examined spectro
scopically for m ercury vapour. A t 80° the discharge is of the arc type, b u t shows some first order spark rays, whilst a t 150° it becomes molecular in type, and band spectra, due probably to rapid distillation of the m ercury, appear. A list of bands obtained between 2345 and 4132 A. is given. These could be produced by feeble or strong excitations which resulted in a green or white radiation, respectively, corresponding w ith different stages of atomic excit
ation. W ith respect to th e ra y 3300 A., the former was the more intense. The m easurem ents agree w ith those of Stark, b u t bands of higher wave-lengths were no t identified. J . Gr a n t.
\
A p p a re n t fa ilu re of th e H u n d th e o ry . A. G.
Sh e n s t o n e (Nature, 1928, 121, 619).— (a) The Paschen s term s in Ne I are 3P and 1P, arising from an electron structure 2p5ns («1=3). The Is term s can be arranged thus : 3P 2= l s 5, 3P . = 1,«4, 3P 0= 1 s 3, 1P 1= 1 « 2- Consequently 3P 2 and ZP 1 converge to one lim it, and 3P 0 and 1P 1 to a higher limit, th e two limits together being the *P(p6) of Ne n . This is in disagreement with th e theory. (b) N i I, Cu II, P d i, and Ag n show sequences of 3D, lD term s of origin (Ps converging to the 2D(d?) of the higher ion. In Cu n , Ni I, and Ag ii only two series members are known, b u t th ey are well verified. In all cases the calculated lim its of 3D3 and 3X>2 fall close together, as do those of 3D 1 and 11)V contrary to th e theory.
A. A. El d r id g e. E x c ita tio n of s p e c tr a b y h ig h -fre q u e n c y o sc ill
a tio n s. J . R . Cl a r k e (Nature, 1928, 121, 282).—
Explanatory (cf. Ponte, this vol., 212).
A. A. El d r id g e. N a tu r a l w id th of th e lin e s of X -r a y s p e c tr a . D. Co s t e r (Z. Physik, 1927,45, 797—800).—A theory of natural w idth of the lines of X -ray spectra is advanced to explain the apparent discrepancies between the experim ental results of Ehrenberg, Mark, and Susich (ibid., 42, 807, 823) and those of Wien (A., 1927, 707). R . W. Lu n t.
D is p e rsio n a n d a b s o r p tio n of „Y-rays. J . A.
Pr in s (Z. Physik, 192S, 4 7 , 479—498).—On th e assum ption th a t th e resonators in the X-level are distributed according to a X3-law, the theoretical dispersion and absorption of X -rays are calculated.
Two sets of formulae are deduced, for long and short waves, respectively. Application of the formula derived to the m easurem ents of Richtm yers on molybdenum, silver, tin, and gold shows th a t for reasonable agreement one electron instead of two m ust be assumed in the X-level. Various curves showing absorption and dispersion as functions of frequency for different degrees of dam ping are given.
IS ext, consideration is given to the so-called total reflexion. Application of Fresnel’s formula yields an expression for the relative intensity a t different glancing-angl.es, an<^ is shown th a t th e absorption a t any particular wave-length m ust exert a p er
ceptible influence on the reflexion conditions for th a t wave-length. In particular, if the reflexion is con
sidered as a function of the wave-length, the effect is m ost noticeable on passing through an absorption
edge for the reflecting element. There are described some new experiments on so-called to tal reflexion of X -rays, th e first reflexion from a steel m irror being studied in the neighbourhood of the /{’-absorption edge for iron. In the first experiment, unfiltered rays from copper, nickel, cobalt, and iron were used, giving tests in both long and sh ort wave-ranges.
In the second and th ird experiments, analysed rays were used, and in th e la tte r a double m irror was utilised, th e separation being varied during th e experim ent. Photographs of all three experiments are given, from which th e ab ru p t alteration a t the absorption edge and disappearance of th e critical glancing-angle for reflexion in th e long-wave case are evident. The dispersion and absorption show a clear influence on the reflexion in good agreem ent with th e theory. However, to get m oderately complete numerical agreem ent for th e actual dispersion it is necessary to assume th a t th e num ber of dispersion electrons in th e /{-level of iron is about 1-3 instead
of 2. A. J . Me e.
A b s o rp tio n of c a rb o n K -r a d ia tio n b y c a rb o n , n itro g e n , a n d ox yg en. H. Ku r t z (Ann. Physik, 1928, [iv], 85, 529—551).—Mass absorption coeffi
cients for air, oxygen, nitrogen, carbon dioxide, carbon monoxide, and ethane have been determ ined for carbon /{-radiation. Atomic absorption coefficients have been evaluated as follows on th e basis of the validity of th e simple ad ditivity law for th e atom ic absorption coefficients in th e molecule : oxygen, 1-58±0-06, nitrogen 0-88±0-05, carbon, in carbon dioxide 0-42;t0-06, in carbon monoxide 0-48±0-06, in ethane 0-54± 0-03x 10~19. The add itivity law is thus valid for very soft radiation, and no definite influence of the chemical linking can be ascertained.
The absorption coefficients follow the rule <xu=
jfcjZ4'4±0'4, k being (l-7 ± 0 -2 )x 10"23 and Z the atomic
num ber. R. A. M o r t o n .
A d d itio n a l lin e s in th e /i- s e r ie s of m o ly b d e n u m a n d th e n a t u r a l b r e a d t h of s p e c tr a l lin e s . B. Da v is and H. Pu r k s (Proc. N at. Acad. Sci., 1928, 14, 172— 178; cf. A., 1927, 804).—Additional lines have been observed near th e ¡32-line and near the ctj- and a2-lines. The w idth of the lines is less th a n th e value to be expected from th e classical theory of dam ping by radiation.
W . E . Do w n e y. /--S e rie s of r h e n iu m . H. Be n t h e (Z. Physik, 1028, 46, 873—877).—The following values have been assigned to th e ¿-series of rhenium from m easure
m ents with a calcite grating for otj, a2, Pj, S2, p3, p4, Ps> Pg> Ps. Y v 72> Vs. Y g : 1429-8, 1440-7, 1235-9, 1203-8, 1217-6, 1256-3, 1174-7, 1248-1, 1198-0, 1058-7, 1029-8, 1023-5, 1034-3 X, respectively.
R. W . Lu n t. P re c is io n m e a s u r e m e n ts in th e rh o d iu m /¿ -se rie s. P . E u g e r (Z. Physik, 1928, 46, 826—
832).— T h e w a v e -le n g th s of th e follow ing rh o d iu m X -lin e s h a v e b e e n d e te rm in e d , u sin g a c a lc ite g r a tin g a n d a n ew fo rm o f th e S ieg b a h n —L a rsso n s p e c tro m e te r : a 2, a ,, 3,, p ., p2, re sp e c tiv e ly 616-371, 612-023, 545-093, 544-491, a n d 533-957 X. R- W. L u n t .
Z e e m a n effect a t in te rm e d ia te s tr e n g th s of m a g n e tic field. K . D a r w i n (Proc. Roy. feoc.,
452 B R IT IS H CH EM ICA L ABSTRA CTS.— A .
1928, A, 118, 264—285; cf. C. G. Darwin, A., 1927;
707).—Mathematical. D arw in’s new formulae (loc.
cit.) for obtaining the frequency and intensity of any component in th e standard Zeeman effect in any strength of field are applied to the s —p and p —cl doublets an d the s —-p triplets, involving 10, 34, and 19 lines, respectively. L. L. Bir c u m s h a w.
Z e e m a n effect of a n in te rc o m b in a tio n lin e . W. C. v a n Ge e l (Z. Physik, 1928, 47, 615—621).— The positions and intensities of the Zeeman-cffect components of the mercury, pzD2, intcrcom bination line have been measured. ’ The intensity formula of Honl (ibid., 1925, 31, 340) was found to hold for the components of an intercom bination line.
W. E. Do w n e y. M e th o d of d e te r m in in g io n is a tio n a n d r e s o n an ce p o te n tia ls . I. H. Ba r t e l s (Z. Physik, 1928, 47, 61—67).—A new m ethod of m easurem ent is described based on the H ertz differential m ethod for resonance potentials which enables th e determ ination of a function, I r, of the voltage, V, accelerating th e electrons which exhibits a maxim um whenever V attain s a value corresponding with an ionisation or a resonance potential. An electron stream is allowed to flow a t one end into a m etal cylinder which is m aintained a t a potential V above th e filam ent; the filament m ust be placed relatively to th e cylinder so th a t th e electrons lose no appreciable fraction of their energy Vc before entering the cylinder. An electrode placed in the cylinder, bu t insulated from it, is m aintained a t a small potential V' (generally a fraction of a volt) above th a t of th e cylinder; th e current, I„„ flowing from this electrode to the cylinder is measured. I t is shown th a t 7r= ( /,„ —I$ J1 0 is a measure of th e num ber of electrons of low energy liberated in th e cylinder as a result of inelastic collisions suffered by electrons of energy V —2 V ’ ; if I r roaches a maximum a t V, this signifies a resonance or an ionisation potential a t V —2 V . I 0 is the current flowing from the collector electrode to the cylinder when the electrode is a t the same potential as the cylinder, V, and V is the value of this potential a t which I,„ has been determined. Lack of uniform ity in the velocities of the electrons entering the cylinder does not shift the position of the m axim a b u t reduces th eir sharpness. R . W. L e n t .
R eso n an c e a n d io n is a tio n p o te n tia ls of a rg o n . H . Ba r t e l s and W. Gl iw it z k y (Z. Physik, 1928, 47, 68—71).—The following values of resonance potentials in argon a t pressures of 0-22 and 0-12 mm.
have been obtained by B artels’ m ethod (cf. preceding abstract) : 11-5, 12-8, and 14-0 volts, in good agree
m ent with the d ata of Hertz. Ionisation potentials were observed a t 15-86 and 16-25 volts, in good agreem ent with the values 15-66 and 15-S4 calculated from spectroscopic data. These m easurements indic
ate th e advantages of the new technique of Bartels, since, in th e older methods, it was impossible to dis
tinguish between two ionisation potentials so closely
placed. R. W. Le n t.
T h e rm io n ic e m is s io n a n d e le c tro n re fle x io n b y m e ta ls . L. No r d h e t m (Z. Physik, 1928, 46, 833—S55).—By assuming th a t the electrons in metals behave as a gas to which th e Eerm i-D irac statistical
calculus m ay be applied, the Richardson-D ushm an formula has been derived. The quantum mechanics of the reflexion of electrons from m etal surfaces are
also discussed. R. W. Lu n t.
E le c tro n ic d is c h a rg e f r o m co ld w ir e s in in te n s e e le c tric field s. R. J . Pie r s o l (Physical R ev.,
1928, [ii], 31, 441—447).—-The curves obtained by -plotting the potential gradient against th e logarithm of th e electronic current for outgassed tungsten a t 27° and — 1S0° are not linear. A. A. El d r id g e.
V elo city d is tr ib u tio n of p h o to -e le c tro n s . E.
He r o l d (Ann. Physik, 1928, [iv], 85, 587—611).—
The velocity distribution of electrons liberated by radiation of wave-length 254 ¡¿¡j. from copper, p la t
inum, aluminium, and lam pblack indicates th a t although the curves are closely similar for the different materials, definite deviations are shown and are greatest a t the smallest and greatest velocities. The velocity distribution with platinum varies with th e gas content, since outgassing shifts the curve a t first in the direction of greater velocities and later again in the direction of smaller velocities. From th e change in th e form of th e curve in th e region of m oderate velocities, it would appear th a t the n atu re of the excited substance definitely influences th e velocity distribution. The use of platinum films of various thicknesses shows th a t the velocity distribu
tion curves are identical for thicknesses varying from 35 to 5-5 fxijt., b u t th a t for thinner films, th e slowest electrons (of about 0-1 volt) undergo retardation.
The absolute values and the distribution of velocities with tungsten layers are independent of the angle of incidence of the light. R. A. Mo r t o n.
In flu e n ce of th e g a s la y e r on th e p h o to -e le c tric s e n s itiv ity of m e ta ls . H . Ivlum b (Z. Physik, 1928, 47, 652—670).—Small pieces of tantalum , tungsten, molybdenum, nickel, and palladium were, in tu rn , heated in an evacuated tube. I t was found th a t in each case the effect of this heating was to move th e lim it of th e photo-electrically effective wave-lengths towards th e short ultra-violet. The ordinarily ob
served photo-electric effects are ascribed as being due to a surface layer of gaseous im purity. F u rth er experiments suggested th a t w ater vapour is peculiarly effective in this respect. W. E . Do w n e y.
I n n e r p h o to -e le c tric effect w ith s ilv e r h a lid e s . S. E. Sh e p p a r d (Nature, 1928, 121, 574—575).—A discussion of two possible views of th e photolysis of silver halide, based on considerations of lattice energy.
A. A. El d r id g e. P h o to -e le c tric th r e s h o ld fre q u e n c y a n d th e th e rm io n ic w o rk fu n c tio n . R. H. F o w le r (Proc.
Roy. Soc., 1928, A, 118, 229—232).—M athem atical.
R ichardson’s suggestions as to the nature of th e
“ free ’’ electrons necessary to explain th e existence of a sharp photo-electric threshold frequency v0 are unnecessarily complicated. I t is shown to follow generally from Sommerfeld’s revived electron theory of m etals, and independently of any p articu lar assum ptions as to the nature of the surface action, th a t there exists a sharp photo-electric threshold frequency v0, and th a t the energy corresponding w ith this threshold frequency is equal to the therm
G E N E R A L , PH Y S IC A L , A N D IN O R G A N IC C H E M IST R Y . 453
ionic work function, i.e., 7w0= / . Sommerfeld’s theory gives an equally satisfactory account of the currents extracted from cold m etals by intense fields.
L. L. Bir c t o is iia w. D ire c tio n s of e m is s io n of p h o to -e le c tro n s . P. A u g e r (Compt. x-end., 1928, 186, 758—760).—
Experim ents on the photo-clectric effects produced by the /{"a-rays of tungsten in argon diluted w ith hydrogen indicate th e need for revision of the theory proposed by the author and F. Porrin (cf. A., 1926, 876). The distribution in space of th e directions of emission of the photo-electrons is unsym m etrical and the emission shows a principal maximum a t an angle of 80°, an d secondary and tertiary m axim a a t 60° and 120°, respectively. An orientation in the absorbing atom m ay determ ine the directions of emission of th e photo-electrons. J . Gr a n t.
E le c tric field s n e a r m e ta llic su rfa c e s . J . A.
Be c k e r and D. W. Mu e l l e r (Physical Rev., 1928, [ii], 31, 431—440).—A study of the fields near metallic surfaces which affect the escape of electrons.
A. A. El d r id g e. S e c o n d a ry e le c tro n c u r r e n t a s a fu n c tio n of c ry sta l s tr u c tu r e . H . E . Fa r n s w o r t h (Physical Rev., 1928, [ii], 31, 419—422).—The view th a t the secondary electron characteristics of copper, in the low-voltage region, are a function of the arrangem ent of the atom s a t the surface, and are n o t directly dependent on the structure of the atom s themselves, is supported by the results of com parative experiments with phosphor-bronze, sheet copper, and single-crystal
copper. A. A. El d r id g e.
E n erg y d is tr ib u tio n of s e c o n d a ry e le c tro n s fro m co p p er, iro n , n ic k e l, a n d silv e r. H. E.
Fa r n sw o rth (Physical Rev., 1928, [ii], 31, 405—
413).—The energy-distribution curves vary with the metal and w ith its h e a t treatm ent. There is no evidence of tllo existence of inelastic collisions:
A. A. El d r id g e. L a rg e a n g le s c a tte r in g of lo w -v e lo c ity e le c tro n s fr o m co p p e r, iro n , n ic k e l, a n d s ilv e r. H. E . Fa r n s w o r t h (Physical Rev., 1928, [ii], 31,414—41S).
E le c tro n ic c o llisio n s in a g a s -fille d sp ace. M.
Pi r a n i and H. Sc iio n b o r n (Naturwiss., 1927, 15, 767—768; Chem. Zentr., 1927, ii, 2261).—The P.D.
produced when two concentric cylindrical electrodes of tungsten and molybdenum, respectively, arc placed in an atmosphere of hydrogen or-nitrogen a t 1600—
2000° Abs. is 30 millivolts or 50 millivolts, an electron current passing from the tungsten to the molybdenum.
W hen the circuit is closed; the current increases with rise of tem perature. W ith an applied potential nitrogen, b u t not hydrogen, exhibits a saturation
value. A. A. El d r id g e.
C ollision s b e tw e e n e le c tro n s a n d g a s m o le cu les. I. Langm cjir and H. A. Jo n e s (Pli37sical Rev., 1928, [ii], 31, 357—404).—By the use of positive ion sheaths as perfcct grids, d ata have been obtained regarding the ^probability of collisions between elec
trons of 30 250 volts velocity and mercury, hydrogen, nitrogen, helium, neon, and argon m olecules; the m ean angular deflexion for elastic and inelastic col
lisions between electrons and gas molecules has been
calculated. The current density of positive ions has been measured, an d the space potential both measured and calculated. The maximum num ber of positive ions produced by an electron is dependent only on its velocity and the nature of the gas. Values of the m ean free p a th for inelastic collisions are tabulated, and the small angular scattering of electrons is dis
cussed. The following resonance and ionisation potentials (volts), respectively, were observed : m er
cury 6-7, 10-4; neon 18-5, 21-5 ; argon 13-0, 15-3;
helium 21-1, 24-5; nitrogen 13-0, 16-S; hydrogen 12-8, 16-1. A. A. El d r id g e.
R e la tio n b e tw e e n effective m o le c u la r d ia m e te r a n d q u a n tu m c h a n g e s. E . Br ü c h e (Z. Physik, 1928, 47, 114— 130).—The significance of various definitions of the effective molecular diam eter of gases as a function of the velocity of colliding electrons is discussed. A relation is sought between the v aria
tion of the effective molecular diam eter ■until electron velocity and th e quantum energy changes th a t m ay occur corresponding w ith resonance and ionisation
potentials. R. W. Lu n t.
R e c o m b in a tio n of io n s a n d e le c tro n s . J . Fr a n c k (Z. Physik, 1928, 47, 509—516).—Using the hypothesis th a t an electron set free by some ionisation process from the positive ion can recombine with the emission of radiation before it has got out of the sphere of influence of the atom , the investigations of variation of intensity of a spectral line with the kinetic energy of the electron stim ulating it are con
sidered : (a) those in which the energy of the prim ary electron only ju st exceeds the necessary energy for the excitation of th e given line ; (b) those in which fast electrons are employed. The 'explanation of th e form of variation a t high electron velocities is made possible by th e original assumption. The probabilities of the various processes th a t would be involved are considered, an d the possibility of u ltra violet an d infra-red stim ulation is mentioned. In th e second p art, triple collisions are assumed between positive ions and prim ary and secondary electrons.
Langm uir has shown th a t cathode rays in a highly ionised gas possess Maxwellian distribution of trans lational velocity over a certain length of their travel.
The length of travel for which this is so, and the m ean energy of the particles, depend on the current strength in th e tube. If there are sufficient triple collisions the prim ary electrons thereby obtain all possible values of energy, and hence from the laws of probability there is a Maxwellian distribution. .
A. J . Me e. M e a n fre e p a t h of th e a lk a li [m eta l] io n s in d iffe re n t g a s e s . R . B. Ke n n a r d (Physical Rev., 1928, [ii], 31, 423— 430).—W ith cæsium ions (90 volts) in hydrogen or helium, there is little neutralisation or scattering; there is a loss of velocity of 1-3 volts per collision. Cæsium ions (35 volts): in hydrogen are slowly weakened by neutralisation or scattering.
In argon, cæsium ions (90, 35, or 20 volts) are rapidly neutralised. Sodium ions of 455 volts velocity suffer weakening in hydrogen. The free paths are given in term s of those of xenon atoms. A. A. El d r id g e.
M o b ilitie s of g a se o u s io n s in h y d ro g e n s u lp h id e -h y d ro g e n m ix tu r e s . L . B.. Lo eb- and
454 B R IT IS H CH EM ICA L A BSTRA CTS.— A .
L. D u Sa u l t (Proc. N at. Acad. Sei., 1928, 1 4 , 192—
199; cf. A., 1926, 449).—Mobilities in hydrogen sulphide and hydrogen sulphide-hydrogen m ixtures have been measured. A t low pressures the inverse pressure law does not appear to hold accurately for the positive ions, whilst it appears to hold for the negative ions. Free electrons were observed in hydrogen sulphide below 50 mm. Thus, hydrogen sulphide is between air and oxygen in its power of attaching electrons to form ions. W. E. Do w n e y.
C ath o d e s p u tte r in g . A. Gü n t h e r-Sc h u l z e (Z.
tech. Phys., 1927, 8 , 169—178; Chem. Zentr., 1927, ii, 385).—The effect is ascribed to volatilisation of the cathode by the impinging cations; the greater p a rt of th e gaseous atoms returns to the cathode by diffusion, b u t a small p a rt escapes. This portion is the greater the smaller is the gas pressure, the greater is th e p artial pressure of the gaseous m etal, and the nearer is the collecting plate. Chemical reaction with form ation of volatile compounds between th e cathode m aterial and the filling gas also increases the sp u tter
ing : the formation of a layer of a compound of high heat of volatilisation, e.g., alum ina, decreases it.
A. A. El d r id g e. O sc illa to ry io n is a tio n c u r r e n ts f r o m clo u d s of c a d m iu m o x id e p a r tic le s . H . P . Wa l m s l e y (Phil.
Mag., 1928, [vii], 5 , 561—573).—The ionisation cu r
rents from cadmium oxide clouds dispersed from an arc have been found to fluctuate rapidly. The m ag
nitude of the effect has been compared w ith th a t to be expected from the theory of chance fluctuations, and it is concluded th a t the fluctuations represent tim e changes in the ionisation density of the cloud.
The currents m ust arise from the breaking down of unstable complexes produced during the coagulation of the cloud, and it is thus concluded th a t th e fluc
tuating current arises from the superposition of cur
rents corresponding with successive groups of unstable
particles. A. E. Mit c h e l l.
D ifferen t m a g n e tic s ta te s of th e c o b a lto u s ion.
A. C h a t illo n (Ann; Physique, 1928, [x], 9, 187—
260).—The tem perature coefficient of magnetisation of the cobaltous ion has been investigated. In aqueous solutions Co + + has an atom ic magnetic m oment of 25 magnetons and a negative Curie point, —12° Abs., independent of concentration and of the nature of the anion. In alcoholic solution the corresponding num ber is 23. Anhydrous sulphates, if the tem per
ature of calcination does not exceed 400°, generally have a magnetic moment of 25 and a Curie point a t
—20° to —30° Abs. If the salt is calcined a t a red heat the magnetic m oment is 26 and the Curie point —50°
Abs. This transition is purely a tem perature effect.
In all, including solutions in aqueous hydrochloric acid, live different magnetic moments of Co++ have been found : 22, 23, 24, 25, and 26 magnetons, respectively. Fractional moments, 23-5 and 25-6, are probably due to mixtures. C. W. Gib b y.
C o lo u r a n d m a g n e tis m of io n s. G. J o o s (Ann.
Physik, 1928, [iv], 8 5 , 641—642).—Recent work on the spectra of T i++ and T i+ + + (Astrophys. J ., 1927, 6 6 , 13) lends strong support to the conclusion (A., 1927, 94) th a t the carriers of colour and magnetism
for the ions of the transition elements cannot be simple ions and m ust be complex molecules.
R. A. Mo r t o n. M e a s u re m e n t of th e m o m e n ts of ir o n a n d n ic k e l a t lo w te m p e r a tu r e s . P. We is s and R.
Fo r r e r (Compt. rend., 1928, 1 8 6 , 821—823).—The atomic moments of iron and nickel have been d eter
mined from the saturation m agnetisation a t the absolute zero of tem perature, this being derived from the m agnetisation measured in a field Ii, a t a tem perature T by double extrapolation towards / / = co and T = 0. The to tal error of the measurements was about 0-2% (including th a t due to impurities) and atomic moments of 11 and 3 m agnetons were found for iron and nickel, respectively. The value for the magneton of 1126-6 obtained in the case of iron is in agreement with recent determ inations. J . Gr a n t.-
E x te n s io n of L a n g e v in 's th e o ry of a to m ic m a g n e tis m to m o le c u le s c o n s titu tin g e le c tro n ic is o m e rid e s . S. S. Bh a t n a g a r and C. L. Dh a w a n
(Phil. Mag., 1928, [vii], 5 , 536—545).—The m agnetic susceptibilities of a num ber of compounds are shown to correspond closely with the expression Xm=
—2-85 X 1010S(ii'?:1)2, where represents the value of the molecular radius given by (>'13-f»'23+ • • • •)v3>
where r v r2, etc. are the atomic diam eters of th e elements forming the molecule and K is an arb itrary constant. K is characteristic of a given group of electronic isomerides, whilst in isomorphous series it is proportional to the atomic numbers.
A. E. Mit c h e l l. S o u rc e of m a g n e tis m d u e to a to m ic s tr u c tu r e . K . Ho n d a (Z. Physik, 1928, 47, 691—701).—Theo
retical. W. E. Do w n e y.
P o la r is a tio n of c a n a l-ra y lig h t in w e a k e le c tric field s. I. H/3-R a d ia tio n in a tr a n s v e r s e field . E. Ru p p (Ann. Physik, 1928, [iv], 8 5 , 515—528).—
The polarisation ratio Ip /I, (IP being th e intensity parallel to, and I s th a t a t right angles to th e ray axis), of the H/j-line from canal-ray light in weak electric fields; has been determ ined for various fields and velocities. W hen th e polarisation ratios for points along th e canal-ray stream are plotted against the distance, th e curves exhibit characteristic periodicities, which become more marked w ith decreasing velocities and increasing fields. The phenom ena are q u alit
atively in accord with th e oscillations of a classical anharm onic oscillator showing different phases along th e stream . ‘ R . A. Mo r t o n.
R a d io a c tiv ity of p o ta s s iu m iso to p e s. M . Bil t z
and H. Ze ig e r t (Physikal. Z ., 192S, 2 9 , 197—200).—
Hevosy (this vol., 4) has prepared potassium chloride w ith an enhanced proportion of th e isotope of atom ic weight 41. The atom ic weight of potassium , instead of appearing to be 39-104 as in ordinary potassium chloride, is 39-109 for this m aterial. The mass spectrograph indicates for ordinary potassium chlor
ide, 95% of K 39 and 5% of K 41, so th a t th e new- m aterial m ust contain 4 -8 + 1 % more of th e heavier isotope th an is present in th e ordinary m aterial. The [3-activity of both preparations has been determined, using a Hoffmann vacuum electrometer, and since th e new m aterial exhibits 4-2+0-8% more activity th a n the old, it is concluded th a t the radioactive
G E N E R A L , P H Y S IC A L , A N D IN O R G A N IC C H E M ISTR Y . 455
constituent of potassium is the isotope of atomic weight 41. , R . A. Mo r t o n.
M e c h a n ism of th e ev o lu tio n of r a d o n fr o m ra d io a c tiv e m in e r a ls in liq u id m e d ia . V.
Sp it z y n (Trav. Radium Minerals radioact., [Russia], 1926, 2, 264—271; Chem. Zentr., 1927, ii, 2442).—
The am ount of radon removed from radioactive minerals in u n it tim e by flowing w ater is independent of the velocity of flow; hence the' radioactivity of radioactive springs m ust fall proportionally to the increase in flow of th e spring. The value increases (up to ten-fold) with increase in fineness of division of the mineral, and (except for thorianite) increases with rising tem perature. The value (at 20°) increases in the o rd e r: sam arskite, thorianite, pitchblende, autunite. In dilute sodium chloride solution larger values, and in kerosene, alcohols, carbon tetrachloride, and ethyl acetate, smaller values were obtained.
Specimens coated w ith paraffin or W ood’s alloy evolved less radon th a n uncoated specimens.
A. A. El d r id g e. N o rm a l r a d iu m s o lu tio n s . W. Bo t h e (Z.
Physik, 1928, 46, 896—898).—D ata relating to sta n d ard radium solutions are discussed which indicate th a t the activity of such solutions up to an age of seven years shows no deviations greater th a n the order of th e experim ental error. R . W. Lu n t.
H alf-value p e rio d of p r o to a c tin iu m . Q u a n tity in u ra n iu m m in e r a ls a n d u r a n iu m re s id u e s . 0 . Ha hn and E. Wa l l in g (Naturwiss., 1927, 15, 803;
Chem. Zentr., 1927, ii, 2272—2273).—The half-value period of protoactinium is determ ined as 20,760 years, corresponding w ith 1-29X 10"7 g. per g. of uranium . The best source of protoactinium is th e Joachim sthal radium residues. The “ residual residues ” contain 185 mg. of protoactinium per to n (1000 kg.).
A. A. El d r id g e. D isin teg ratio n of r a d iu m - E f r o m th e p o in t of view of wave m e c h a n ic s. G. P. Th o m s o n (Nature, 1928, 121, 615—616).—Ellis and W ooster’s result (this vol., 103)-th a t in th e disintegration of radium-iJ the single ß-particle em itted has an initial energy varying from 40,000 to 1,050,000 volts can be recon
ciled with the new wave mechanics.
A. A. El d r id g e. S y n th e sis of a m m o n ia b y a -ra y s . S. C. Li n d
and D. C. Ba r d w ell (J. Amer. Chem. Soc., 1928, 50, 745—748).—A stoicheiometric m ixture of nitrogen and hydrogen, after passing a thin X -ray bulb con
taining radon, contains am m onia; the yields are higher than those found by Usher in stagnant gas (J.C.S., 1910, 97, 389). 1 A bout 0-2—0-3 mol. of ammonia is formed per ion pair produced in the mixture. I t is predicted th a t equilibrium should occur when the mixture contains 9-09% of ammonia by volume. The results agree qualitatively w ith the observed decrease in velocity coefficient in th e decom
position of ammonia by a-rays as a function of the ammonia concentration. S. K . Tw e e d y.
E x a c t d e te rm in a tio n of th e io n is a tio n p r o d u ce d b y sin g le a -p articles. H. Ze ig e r t (Z.
Physik, 192S, 46, 668—715).—The use of a Hoffmann electrometer for photographically recording the ionis
ation produced by single a-particles is described,
together w ith a statistical analysis of th e results obtained w ith a num ber of radioactive substances.
A new radioactive substance which exists as an im purity in zinc is reported. R. W. Lu n t.
H e a tin g effec ts of t h o r iu m a n d r a d iu m p r o d u c ts . S. W. Wa t s o n (Proc. Roy. Soc., 1928, A, 118, 318—333).—M easurements have been m ade of the relative am ounts of heat em itted by radon in equilibrium w ith its products of short life, radium- j3 + C, radium -C, thorium -#-)- C, and thorium-C. The m ethod used was sim ilar in principle to th a t employed by R utherford and Robinson (Phil. Mag., 1913, [vi], 25, 312), and consisted in measuring the change of balance of a W heatstone bridge when two opposite arms were heated by the radioactive substance. The bridge was standardised by a heating coil, m ade as similar as possible to the radioactive source. The results obtained agree w ithin 1 or 2 % w ith th e theoretical values calculated from Hess and Lawson’s d a ta for th e num ber of a-particles em itted by 1 g. of radium per sec., viz. 3-72 x 1010 (cf. A., 1924, ii, 649);
th ey are as follows (g.-cal. per g.-hr. : radon, observed 101-6, theoretical 102-4; radium -Zi+C , observed 43-1, theoretical 43-8; radium -C, observed 42-9, theoretical 43-4; thorium-fi-j-C', observed 50-7, theoretical 49-7 ; thorium-C, observed 47-9, theoretical 47-2. If Geiger and W erner’s value, viz., 3-4 x lO 10 a-particles per sec. per g. (A., 1924, ii, 226), is correct, it follows th a t 10—12% of the heating m ust be caused by easily absorbed radiation which has n o t been taken into account in th e calculations. This would require about 40, 70, and 80 q uan ta per atom for radium , radium-C, and thorium-C, respectively, if the radiation were of a wave-length of 1 A., and correspondingly more quan ta for softer radiation. If such an additional emission of energy does occur, th e proportion which it bears to th e to tal energy m ust be nearly th e same for a large num ber of radioactive products.
L. L. Bir c u m s iia w. P r o b le m of g e o lo g ic a l tim e . I. E v id en c e fr o m ra d io a c tiv e m in e r a ls . A. Ho lm es (Scientia,
1927, 42, 263—272).—The evidence is considered, and the value 1—1-5 X 109 years is determined.
Ch e m ic a l Ab s t r a c t s. P h e n o m e n a , s i m il a r to th o s e of ra d io a c tiv e b o d ie s , sh o w n b y m e ta ls . (Ml l e.) S. Ma r a- c in e a n u (Compt. rend., 1928, 186, 746—748; cf.
A., 1927, 807).—A continuation of th e experim ents on m etals from th e roof of the Paris Observatory has shown th a t th e activation is n o t due to radioactive du st or em anations from the atm osphere. I t persists for a long period after removal of the m etal from the roof and decreases slowly according to an exponential rule in a m anner comparable w ith th a t of polonium.
Since it is m ost m arked w ith lead, it m ay be due to reintegration of lead into polonium by solar energy with the form ation of radium-Z). This is supported by observations of the a-radiation of polonium.
J . Gr a n t. R a d io a c tiv e r a d ia tio n . K . W. F. Ko h l r a u s c h
(Physikal. Z., 1928, 29, 153—168).—The expression 1 ¡ N . 2 log v (N being th e atomic num ber and v a characteristic frequency in th e sense of the classical dispersion theory) enters into B ohr’s formula; for the
450 B R IT IS H CH EM ICA L A BSTRA C TS.— A .
energy loss and ionisation -which occur w ith tho passage of a- and p-particlcs through m atter. Certain assumptions m ake possiblo a theoretical trea tm e n t which can be tested by m eans of tho d a ta 011 th e energy losses, ranges, and ionisations effected -with a- and p-particles of various velocities, penetrating various m aterials. Agreement of a high order is always obtained, b u t although some instances of rem arkably good verification are observed, i t is no t in general possiblo to evaluato atom ic constants.
This lim itation arises from tho fact th a t the theory applies only to particles of high velocity and to atoms of low atom ic number. Nevertheless th e success achieved by using only th e sim plest scheme indicates th a t th e Bohr theory has great valuo as a principle for introducing order. R. A. Mo r t o n.
L iq u id s t a r s a n d a to m ic v o lu m e . A. S.
Ed d i n g t o n (Nature, 1928, 121, 496).
[L iq u id s t a r s a n d a to m ic v o lu m e .] J . H.
Je a n s (Nature, 192S, 121, 496—497).
S tr u c tu r e of a n a to m of n itro g e n . V II. H.
Collins (Chem. Newrs, 1928, 136, 17S— ISO).—
Speculative.
E q u ip o te n tia l s u rfa c e e le c tro n s a s a n e x p la n a tio n of th e p a c k in g effect. W. E . De m in g
(Physical Rev., 1928, [ii], 31,453—465).—Theoretical.
W ith static models of the helium nucleus, packing can bo satisfactorily accounted for by postulating th a t tho electrons and protons shall bo equipotential surface distributions having the usual to tal charges and radii, whereas ordinary electrons account for only 10% of the effect. W ith dynamic models, neither kind offers a solution. A. A. El d r id g e.
S ta tis tic a l m e th o d fo r d e te r m in in g c e r ta in p r o p e r tie s of th e a to m . I. E . Fe r m i (A tti R.
Aecad. Lincei, 1927, [vi], 6 , 602—607).—M athe
matical. A statistical m ethod for calculating the distribution of the electrons round the nucleus of an atom is developed. From tho result attained, it is possible to calculate the energy required to ionise tho atom completely, th a t is, to strip it of electrons, and also to determine the variation in potential a t different distances from the nucleus and, thus, th e electric field in which the electrons of the atom occur.
T. H. Po p e. Q u a n tu m th e o ry of th e c a p tu r e of e le c tro n s . J . R. Op f e n h e im e r (Physical Rev., 192S, [ii], 31, 349—356).—The m ean free p ath for the capture of electrons from atoms by a-particles is com puted to v ary approxim ately with the sixth power of the velocity of the a-particle, a result in accord with experim ent. The probability of radiative recom bination of electrons and protons is also computed.
A. A. El d r id g e. In te r fe r e n c e of lig h t q u a n ta . A. Pro c a (J.
Pliys. R adium , 1928, [vi], 9, 73—SO).—Theoretical.
If time is taken as one of the co-ordinates in develop
ing the quantum theory, it is found th a t quanta m ust be coherent. W. E. Do w n e y.
Q u a n tu m th e o ry of th e e le c tro n . II . P. A. M.
Dir a c (Proc. Roy. Soc., 1928, A, 118, 351—361;
cf. this .vol., 344).—A continuation of the theory of atom s with single electrons. Proof is given of the
conservation theory, winch states th a t th e change in th e probability of the electron being in a given volume during a given tim e is equal to th e probability of its having crossed the boundary. From a determ in
ation of tho selection rule for j it is found th a t from states with j —2, transitions can take place to states w ith j —1, —2, or 3. This is exactly equivalent to the two selection rules for j and 1c of the usual theory, and is therefore in agreem ent w ith experim ent. To determ ine tho relative intensities of the lines of a m ultiplet on th e x^resent, theory, it is only necessary to consider one Zeeman com ponent of each line. Tho ratios found arc in agreement w ith those of previous theories based on the spinning electron model.
L . L . Bir c u m s h a w. R e la tiv istic q u a n tu m th e o ry of id e a l g a s e s . F . Jü t t n e r (Z. Physik, 1928, 47, 542—566; cf.
A., 1911, ii, 579, 972).—An extension of previous work. M athematical. A. J . M ee.
C e n tra l fie ld s a n d R y d b e rg form u lae in w av e m e c h a n ic s. J . C. Sl a t e r (Physical Rev., 1928 [ii], 31, 333—343).—A theoretical discussion.
A. A. El d r id g e. T h e a s y m m e tr ic tw o -c e n tre p r o b le m a c c o rd in g to th e w a v e -m e c h a n ic s a n d its a p p lic a tio n to c r y s ta l th e o ry . S c a tte r in g p o w e r of a to m s . K . F. Nie s s e n (Physikal. Z., 1928, 29, 132— 143).—
The scattering power of the atom in lattices of tho diamond or wurzite type has been calculated using the treatm ent of the two-centre problem given by the wave mechanics. R . A. Mo r t o n.
H e is e n b e rg ’s in d e te r m in a tio n p rin c ip le . E . H.
Iv e n n a r d (Physical Rev., 1928, [ii], 31, 344—348).—
The principle is applied to cases wiiere the position and velocity of an electron are observed by allowing it to pass through shutters opened m om entarily a t known times. A. A. El d r id g e.
D is trib u tio n of m o le c u la r v e lo c itie s, ex c ite d s ta te s , a n d tr a n s itio n p ro b a b ilitie s in d e g e n e r
a te d g a se s. E . Pe r sic o (Atti R . Accad. Lincei, 1928, [vi], 7, 137— 141).—The analyses of Pauli and Ferm i have been extended to derive expressions for th e distribution of molecular velocities and for the probabilities of transition from one energy level to another in a degenerated monatomic gas.
R. W. L p p i.
I n t e r p r e ta tio n of b a n d s p e c tr a . R. d e L.
Kr o n ig (Z. Physik, 1928, 46, 814— 825).—M athem
atical. R. W. Lu n t.
S tr u c t u r e of F ra u n h o f e r lin e s a n d q u a n tita tiv e s p e c tr u m a n a ly s is of th e a tm o s p h e re of th e su n . A. Un s o l d (Z. Physik, 1928, 46, 765—781).—A modified form of Milne’s theory of the radiation equilibria in the atm osphere of the sun has been introduced. Determ inations of the intensity dis
tribu tio n in Fraunhofer lines are described which are held to establish the newer form of the theory. From these d ata it is shown th a t the electron partial pressure in the chromosphere is of th e order of 10~8
atm . R . W. Lu n t.
N itro g e n a fte r-g lo w . J . C. McLe n n a n, R- Ru e d y, and J . M. An d e r s o n (Nature, 1928, 121, 537—538).—Although th e heat of dissociation of
G E N E R A L , PH Y SIC A L , AN D IN O R G A N IC C H E M IST R Y . 457
molecular nitrogen is considered to be equivalent to 11 volts from a consideration of the band spectrum, the intensity distribution in the spectra of radiations from m ixtures of foreign vapours w ith active nitrogen does not accord with tliis value. Experim ents on the addition of xenon and krypton with excess of nitrogen afforded no lines of these elements in the spectrum of the after-glow, whereas addition of m ercury causes the appearance of strong m ercury lines. I t is con
cluded th a t chemiluminescence plays a p a rt in the phenomena associated w ith active nitrogen.
A. A. El b r i d c e. In flu en ce of c o n ta in in g w a lls o n th e a fte r-g lo w of n itr o g e n a n d oxygen. G. He r z b e r g (Z. Pliysik, 1928, 46, 878—895).—The intensity of the after-glow in oxygen, nitrogen, and oxygen-uitrogen m ixtures excited by an electrodeless ring discharge under unspecified conditions has been examined1 in the pressure ranges 0-05— 1-2 mm. I t has been shown th a t the after-glow, particularly in nitrogen, does not occur if th e containing vessel of quartz is heated in a vacuum to remove gases condensed on the surface.
The experiments are held to establish th a t a. surf ace- poisoning of the quartz is essential to production of the after-glow. As th e fraction of oxygen in the mixture is increased the intensity of the nitrogen after-glow diminishes to a minimum and then passes through a m axim um ; correspondingly the intensity of the oxygen after-glow passes through a maximum and falls to a minimum a t the same composition a t which the nitrogen after-glow is a m inim um ; the intensity th en passes through a second maxim um and vanishes in pure oxygen. The percentage of oxygen a t which the intensity of both after-glows reaches a minimum depends on th e to tal pressure of the gas mixture, and shifts towards higher nitrogen concen
trations as the pressure is increased. R. W. Lu n t. M e a s u re m e n t of o x y g en b a n d s in th e v io le t a n d u ltr a - v io le t re g io n s of th e s p e c tr u m . II.
Fe s e f e l d t (Z. wiss. Phot., 1927, 25, 33—60).—Tables are given showing the results of measurem ents of the oxygen bands discovered by R-unge and Grotrian {Physikal. Z., 1914, 15, 545; Runge, Physica, 1921,
1 , 254) in the region 3140—4450 A. The line intensi
ties, frequencies, and the mean errors of measurement
are also given. W. Cl a r k.
In te rc h a n g e a b ility of zin c o x id e a n d dy es in o p tic a l se n s itis a tio n . C. Ne u w e il e r (Z. wiss.
Phot., 1928, 25, 187-—224).—In light, zinc oxido acts on aqueous solutions of organic dyes of widely different classes. In pure, air-free aqueous solution the dyes are both oxidised and reduced. In presence T irt? anoc^c depolariser they are exclusively reduced, u itli v at dyes, photolysis still occurs even a t the highest reduction potentials (safranin, s„ = + 0 -1 5 volt.
< ^crences °f potential (up to about ) between the anodic and cathodic photolysis processes can be overcome by light. W ith azo-dyes the photolytic reduction is not reversible; i.e., the i eduction products wore not reconverted into dyes by the oxygen of the air. The alkalinity of the zinc
oxk e, aucUiesiting, play no p a rt in the reactions studied. Under certain conditions, sensitising dyes can exert the same photolytic effect on organic dyes
as zinc oxide. The necessary condition is th a t the absorption region of th e sensitiser m ust coincide w ith th a t of the acceptor on th e short wave-length side.
W. Cl a r k. A b s o rp tio n s p e c tr a of p h o to -e le c tric a lly c o n d u c tin g c r y s ta ls . R. O ttm e r (Z. Physik, 46, 798—813).—The extinction coefficients of the follow
ing substances have been determ ined in the range 2000— 9500 A. after colouring duo to oxposure to hard X -r a y s : lithium chloride and fluoride; sodium fluorido, chloride, and brom ide; potassium fluoride, chloride, bromide,, and iodide; rubidium chloride.
The position and value of th e m axim um in the region 5000—6000 A. areunaffectedbythedegreeof coloration of the salt. The m axim um a t 4700 A. in rock salt is diminished by exposuro to blue lig h t; m easure
m ents of th e conductivity of rock salt during exposure to light of different wave-lengths shows th a t th e absorption in th e neighbourhood of 7200 A. is u n connected with th e conductivity. R . AY. L u n t.
A lk a lin e - e a rth h a lid e s p e c tr a and. t h e i r o rig in . 0 . H. Wa l t e r s and S. Ba r r a t t (Proc. Roy. Soc., 1928, A, 118, 120—137).—The bands in the spectra of the alkaline-earth halides can be very conveniently observed in absorption against a continuous back
ground spectrum . The absorption spectra observed were those of a column of vapour about a foot long, a t a tem perature of 1000-—1200°. The continuous background spectrum was provided by a 500 candle- power “ Pointolite ” lamp, down to 3800, and by the positive crater of a carbon arc down to 2200. F or the calcium and magnesium halide spectra, excess of calcium: or magnesium turnings was heated w ith the powdered and dehydrated m etal halide salt. The strontium and barium , vapours were obtained by heating a m ixture of metallic calcium and th e strontium or barium halide. Evidence is given in support of the view th a t th e bands originate, no t from norm al halide molecules, b u t from subhalide molecules of the type MX. I t is highly probable th a t such mole
cules exist in the. vapour state a t 1000° in equilibrium w ith the m etal and norm al salts. The ease of preparation of these salts appears to increase w ith the atomic weight of the halogen, as found by Guntz (A., 1924, ii, 610). All th e molecules except those of th e magnesium halides have band groups in the visible region. In general, th e group of largest w ave
length in each spectrum consists of bands degraded to th e short wave-length side. The n ex t group—
usually in th e near ultra-violet—is degraded to the short wave-length side. W hen other groups were found in absorption, the direction of degradation alternated from one group to th e next. New groups of bands have been detected in the ultra-violet, bu t these do no t appear to be arranged according to the R ydberg series law, and it is concluded th a t the various groups of bands in the spectra do no t correspond with successive members of a single atomic line series, b u t rath er w ith th e first members only of several such series. The bands obtained in absorption were com
pared w ith th e corresponding emission spectra from flames and arcs, and in general no differences in structure or intensity distribution were observed.
The structure of the calcium siibfiuoride band a t .5292,
