BRITISH CHEMICAL ABSTRACTS
A . - P U R E CHEMISTRY
FEBRUARY, 1931.
G en era l, P h y s ic a l, and
Is o to p e e ffec t o n b a n d s p e c tr u m in te n s itie s . J . L, Du n h a m (Physical R ev., 1930, [ii], 36, 1553—
1559).—Theoretical. I n order to discover w hether th e transitio n probability of a given Une is different for two isotopic molecules, th e effect of th e nuclear
‘mass on intensities is calculated on the basis of H utchisson’s expressions for the vibrational transition probability (cf A., 1930, 1331). I t is shown th a t there is a change in th e vibrational, b u t no t in the electronic, p a rt of th e transition probability with nuclear mass. The effect of a change in nuclear mass on th e population, regarded as a simple Boltzm ann distribution, of th e initial sta te is also found. Results are applied to find th e m agnitude of the isotope effect for certain bands which have been used to measure th e abundance of th e isotopes in oxygen (cf. Babcock, A., 1929, 971), nitric oxide (cf. N audé, A., 1930, 1232), and chlorine (cf. E lliott, ibid., 977). The effect is small, and generally less th a n 10%. N. M. Bl i g h.
C h a n g e in e le c tro n c o u p lin g i n r a r e g a se s.
C. J . Ba n k e r (Naturwiss., 1930, 1 8 , 1100).—The extension to p ss and d9s configurations b y Laporte and IngUs (A., 1930, 971) of th e quantum -m echanical theory of H ouston (A., 1929, 480) on the relation between th e trip le t interval ratio to the singlet-triplet interval for two-electron configurations in which one electron is in an s-state has been applied to the rare gases: E xperim ental results of B ack (A., 1925, ii, 341) for th e g values of the singlet and middle triplet levels of the 2p53s configuration of th e Ne I spectrum have been com pared w ith calculated values. E x perim ental d a ta on th e Zeeman effect were used to derive g values of analogous levels of th e configur
ations 3pHs in th e A i and 4p55s in the R r I spectra.
In th e spectrum of X e i only th e g values of the middle trip let level of the configuration 5p66s could be measured. F o r th e spectra of Ne I, A i, K r I, good agreem ent was found between calculated and experim ental g values ; w ith Xe i the agreem ent is not
so good. W. R. An g u s.
M e th o d of a p p ly in g th e s litle s s s p e c tr o g r a p h to th e m e a s u r e m e n t of th e D o p p le r sh ift. N.
De i s c h (J. O pt. Soc. Amer., 1930, 2 0 , 685—692).—
Descriptive. W . Go o d.
U ltr a - v io le t l i g h t th e o r y of au ro rae a n d m a g n e tic s t o r m s . E . O. Hu l b u r t (Physical Rev., 1930, [ii], 3 6 , 1560— 1569).—Various difficulties and anom alies in the recently proposed th eo ry (cf. ibid., 1929,3 3 , 412 ; 3 4 , 344) are rem oved b y th e application of further developm ents of th e theory of th e high atm osphere (cf. A., 1930, 392). N . M. Bl i g h.
l
In o r g a n ic C h e m istr y .
P a s c h e n - B a c k effec t in h y p e rfin e s tr u c tu r e . S. Go u d s m i t and R . F . Ba c k e r (Z. Physik, 1930, 66, 13—30).—-The m ethod developed by Heisenberg and Jo rd a n and by Darwin for th e P aschen-B ack and Zeeman effects in ordinary m ultiplets is applied to th e interaction of nuclear spin and re su ltan t outer electronic angular m om entum , to give th e P aschen - Back and Zeeman separations and com ponent line intensities. The theory is accurate only when th e Paschen-B ack effect, is fully developed, and lines of small hyperfine separation should, therefore, be chosen for its verification. Two rules are deduced for tra n si
tio n from strong to weak fields, viz., (i) th e projection, il/p, of th e resu ltan t of all angular m om enta in th e field direction rem ains u n chang ed; (ii) different levels w ith the same value of M F do n o t cross over in energy value. The theoretical results are com pared w ith B ack’s experim ental results for bism uth (cf. this vol.,
137). A. B. D. Ca s s i e.
E x te n d e d e n e rg y fu n c tio n s of th e h y d ro g e n m o le c u le . P . M. Da v i d s o n and W . C. Pr i c e
(Proc. R oy. Soc., 1930, A, 130, 105— 111).—M athe
m atical. A form ula is deduced for th e potential energy of a diatom ic molecule which holds for all values of th e internuclear distance. Previous for
mulae fail either a t small distances, or a t large dis
tances, or both. The present form ula appears as the sum of tw o series, the significance of which is dis
cussed in term s of th e forces between th e com ponents of th e molecule. L. L. Bi r o u m s h a w.
N e w b a n d s in th e s e c o n d a ry s p e c tr u m of h y d ro g e n . I I I . D. B. De o d h a r (Phil. Mag., 1930, [vii], 10,1082— 1095; cf. A., 1930, 263; Finkelnburg, A., 1929, 118).—T he wave num bers, estim ated in
tensities, term values, an d qu antum analysis of the recently discovered group of seven bands in the violet region are tab u lated and discussed.
N. M. Bl i g h. E ffe c t of c r o s s e d e le c tric a n d m a g n e tic field s o n th e B a l m e r lin e s of h y d ro g e n . W. St e u b i n g
(Naturwiss., 1930, 18, 1098— 1099).—The effect of th e sim ultaneous action of an electric and a m agnetic field has been studied. A crossed field does n o t produce new components, b u t there results a kind of displacem ent of S tark effect components which follows identically th e intensity changes of individual com ponents. T he results on th e in ten sity differences of com ponents in relation to the direction of the electric field are of im portance in deciding w hether experim ent
al results on the in ten sity distribution of S tark effect com ponents are in harm ony w ith th e theory of 135
1 3 6 B R IT IS H CH E M IC A L A B ST R A C T S.— A .
Schrödinger. W eak m agnetic fields do n o t ex ert a m arked influence on th e intensity distribution.
W. R . An g u s.
E x p e r im e n ta l a r r a n g e m e n t of th e H , b a n d s y s te m in to s in g le t a n d t r i p l e t s y s te m s . W.
Fi n k e l n b u r g (Z. Physik, 1930, 66, 345—349).—The distinct forms of the excitation function-exciting voltage curves for singlet and trip let term s were used to distinguish H 2 singlet and trip let b a n d s ; A'-, /1-bands belong to a singlet system, an d cc-, ß- to a trip let system . The subsidiary m axim um which appears only in th e H 2 trip let excitation function-exciting voltage curve is in accord w ith B eutler and Eisenschimm cl’s hypothesis th a t during a collision process th e re su ltan t electron spin of th e colliding entities m ust rem ain
unchanged. A. B. D. Ca s s i e.
S ta r k e ffec t in s o m e h e liu m lin e s in th e v is ib le s p e c tr u m . K . Sj ö g r e n (Z. Physik, 1930, 66, 377—
388).—The S tark effect was determ ined quantitatively, b y S ta rk ’s original m ethod, for fields of 175—550 kilovolts per cm. The lines 2 S —3P, 2 S — 3D, 2P — 4S, 2P -4 rD , 2 P - 4 F , 2 P - 4 P , 2 p ~ 4 s, 2 p - 4 d , 2 p —4f, and 2 p —4p were investigated.
A. B . D. Ca s s i e.
C h a n g e in e le c tro n c o u p lin g in th e r a r e g a s e s . C. J . Ba r k e r (N ature, 1930, 126, 955).—From experim ental d a ta on th e Zeeman effect of the rare gases, th e experim ental g values of th e analogous levels of th e configuration 3pHs in A i and 4 p 55s in K r i are obtained. A greem ent between observed and calculated g values is satisfactory in the case of Ne i, A i, and K r i. L. S. Th e o b a l d.
N u c le a r m o m e n t of L iß a n d L i7. H. Sc h u l e r
(Z. Physik, 1930, 66, 431— 435).—Hyperfine stru ctu re of th e Li n 5485 A. line was investigated by m eans of a P e ro t-F a b ry etalon w ith a m axim um plate separation of 3 mm. R esults for L i7 agree approxim ately w ith G üttinger’s formulae (cf. A., 1930, 1487) for nuclear spin of 4 and of § units, b u t do n o t give sufficient detail to decide between th e two values.
Li6, 5485 Ä., has no hyperfine stru ctu re of separation greater th a n one fifth th a t of Li7.
A. B . D. Ca s s i e.
C i v lin e s i n th e v is ib le a n d n e a r u ltr a - v io le t.
T e r m s y s te m fo r C iv . B. Ed l e n and J . St e n m a n
(Z. Physik, 1930, 66, 328— 338).—The spectrum due to a carbon arc acting in a vacuum was examined.
T h espark lines C i, C n, C m ,andC ivw eredisting uished b y their separate variations in intensity w ith variation of th e self-induction of th e discharge circuit. New CI I and C m lines, and the m ost intense C iv lines due to transitions between orbits of to tal quantum num ber 4 and 5, and 5 and 6, were observed. These lines were arranged into a term system, which in cludes m ore accurate values of term s of principal quantum num ber 6 th a n have hitherto been given.
T he doublet separations in 22P , 32P , and 4-P fit L ande’s formula. A. B. D. Ca s s i e.
N u c le a r s p in of n itr o g e n . W . R. v a n W i j k
(Arch. Nderland., 1930, [iiiA], 13, 29—57).—The general theory of diatom ic m olecular spectrum s tru c tu re is briefly surveyed. M easurements were m ade of the negative band spectrum of nitrogen due to th e N 2+
molecule, and of the second positive group due to the n eu tral molecule. The value 2 : 1 was found for th e ra tio of altern atin g intensities of th e negative bands 3914, 3SS4, 427S, an d 4237 A., an d for th e positive bands 3371, 3805, an d 3755 A. From investigation on th e 3914 band, th e ra tio was found to be indepen
d en t of th e pressure. The agreem ent of intensity m easurem ents w ith other criteria for nuclear spin value was investigated from- th e 3776 A. thallium line, which showed strong absorption and confirmed th e value 4 for th e nuclear spin. N. M. Bl i g h.
B e r g m a n n s e r ie s i n th e a r g o n s p e c tr u m . E.
Ra s m u s s e n (Naturwiss., 1930, 18, 1112— 1113).—
Among th e in ert gases B ergm ann series had been observed in the spectrum of xenon only. The corre
sponding series has been obtained in th e argon spec
tru m , which was photographed on negative plates, using a plane grating spectrograph (dispersion 17A./m m .).
A table of the observed series is given. The lim iting term s 3de, 3d-, 3d3, 3d1,, 3d, and th e term series niU a n d m W have been determ ined. Certain new com binations of principal an d subsidiary series have been found and are tab u lated . From these com bin
ations the term s 2 s,, 2s3,2s4,2s5,an d 3 s"w ere evaluated.
W ave-lengths greater th a n 1 a have been provisionally m easured by extrapolation. W . R . An g u s.
S tr u c t u r e of th e ir o n s p e c tr u m . M. A. Ca t a l a n
(Anal. Fis. Quinn, 1930, 28, 1239— 1385).—A comprehensive survey, w ith a bibliography, is given of previous work on th e atom ic stru ctu re of iron, w ith extensive tables of th e wave-lengths an d intensities of all th e arc lines recorded, an d of th e Zeem an effect. More th a n 2350 lines of th e F e I spectrum are classified in 304 levels, and th ere are 8 series, 51 term s, and 275 m ultiplets. I t is shown th a t th e m ost intense lines originate by addition of a valency electron to th e atom ic residue in one or both of the spark configurations 3d°4s and 3d7.
H . F . Gi l l b e.
I n te n s ity m e a s u r e m e n t s of th e m u l ti p l e t z 5G —e5F. W. A. M. De k k e r s an d A. A. Kr u i t h o f
(Z. Physik, 1930, 66, 491— 493).—In ten sity relations in the z5G—ebF m ultiplet of nickel were determ ined from a carbon arc, one of the poles of which contained a nickel bead, or alternatively, 10% of nickel su lp h a te ; th e other pole was either of carbon or of a nickel-zinc alloy. Deviations from th e sum m ation rule always
occurred. A. B. D. Ca s s i e.
I n te n s ity m e a s u r e m e n t s of th e c o p p e r a r c lin e s . L. S. Or n s t e i n an d D. Ve r m e u l e n (Z.
Physik, 1 93 0,66,490; cf. A., 1930,1329).—Copper in a carbon arc gives th e ra tio of intensities of th e 12£ — 2?P copper doublets as 1 :2 , which agrees w ith th e sum m ation rule value. A. B. D. Ca s s i e.
S e r ie s of th e s ilv e r a r c s p e c tr u m , A g i. H . A.
Bl a i r (Physical R ev., 1930, [ii], 36, 1531— 1534;
cf. A.. 1930, 1227).—The high series m embers of Ag i were measured, using a Schüler tu be source and helium standards. D a ta for th e com plete diffuse, sharp, and principal series are tabu lated , including a few new lines, and correcting existing values. No term s of th e quadrup let system nor of th e d9s2 -D were found (cf. McLennan, A., 1928,1167; Shenstone, ibid.,
G E N E R A L , P H Y S IC A L , AN D IN O R G A N IC CH EM ISTR Y ’. 137
450). R itz formula! for the series were d ed uced; the value of th e lowest term d10os2S is 61104-4, giving an ionisation potential of 7-53 volts. N. M. Bl i g h.
B a n d s p e c tru m of silv e r h y d rid e . E. Be n g t s-
s o n (N ature, 1931, 1 2 7 , 14).—The rotational stru c
ture of 14 bands belonging to — -v1!! have been analysed an d arranged in a vibrational scheme.
The vibrational levels of th e lower electronic state can be represented by th e form ula F " ( v ) = 1723-5?/'—
33-5u"2—0-0094«"3 ; th e excited electronic state shows certain irregularities which m ay originate from a perturbing level. The dissociation energies in both states are 7 )'~ 6300 and D " ~ 19,000 cm."1 approxim
ately. L . S. Th e o b a l d.
Effect of g a s e s on th e op tically excited c a d m iu m I sp e c tru m . P. Be n d e r (Physical Rev., 1930, [ii], 3 6 ,1535— 1542).—A n app aratu s is described for producing intense optically-excited cadmium radiation for an investigation of the quenching effect of nitrogen, carbon monoxide, and hydrogen on the optically excited cadm ium spectrum . Each gas decreases th e inten sity of each of the spectral lines.
Nitrogen and carbon monoxide have a low quenching efficiency, th e former being th e less efficient, and are less effective in quenching th e resonance line A 3261 th an th e rem ainder of the spectrum . Kinetic energy collisions of molecules of these gases with excited cadm ium atom s transfer them from the 23P 1 to the m etastable 23P 0 state. H ydrogen has a high quenching efficiency, collisions w ith th e 23P 1 cad
mium atom s form ing cadmium hydride molecules and atomic hydrogen (cf. B ates, A., 1929, 156). The effects are com pared w ith sim ilar phenom ena for mercury (cf. K lum b, ibid., 480). N. M. Bl i g h.
O ptical e x c ita tio n of c a d m iu m h y d rid e an d zinc h y d rid e b a n d s. P. Be n d e r (Physical Rev., 1930, [ii], 36, 1543— 1552; cf. preceding abstract).—
Excitation of a cadm ium -hydrogen gas m ixture with light from a hydrogen-cadm ium , b u t n o t from a helium -cadm ium , discharge produces an intense true optical resonance of cadm ium hydride b an d s; these are produced also through excitation of CdH molecules by collisions of th e second kind between excited cadmium atom s and either norm al CdH molecules or H2 molecules. The m echanism of th e resonance excitation is discussed. Zinc hydride bands were produced as tru e optical resonance radiation by hydrogen-zinc electric discharge. M ercury hydride bands were excited, using a water-cooled m ercury arc, through collisions of th e second kind (cf. Gaviola and Wood, A., 1929, 239) and th e mechanism is discussed in relation to th e foregoing results. N. M. Bl i g h.
P h o to -e le ctric in te n s ity m e a s u re m e n ts in the m e rc u ry s p e c tru m . II. L . S. Or n s t e i n and J . F. Cu s t e r s (Proc. K . Akad. W etensch. Am sterdam , 1930, 33, 809—813).—F u rth e r m easurem ents on the intensity of certain lines in th e m ercury spectrum have shown th a t the relations previously reported (A., 1930, 1080) hold n o t only for the pressure region investigated, b u t also a t very low pressures, the measurem ents having been extended by th e use of a more sensitive photo-electric cell. W ith falling pressure the peak of th e curve connecting potential
with curren t density is displaced in th e direction of higher curren t density, b u t th e peak p otential falls a t first an d rises again later. The intensity, I , of the line 5461 A. has been m easured as a function of the current density i, and a t all pressures the ratio I¡ i increases w ith decreasing cu rren t density.
E . S. He d g e s.
F lu o rescen ce of ex cited m e rc u ry a to m s. Z.
Za j a c (Compt. rend., 1930, 191, 1304— 1306; cf.
Pienkovski, A., 1928, 813).—M ercury vapour was excited sim ultaneously by an oscillating electric discharge and a low-pressure m ercury arc in an evacuated sealed tu be connected w ith a m ercury reservoir, both of which could be heated independ
ently so as to v ary either the vapour pressure (t° const.) or th e density (p const.). A bluish-green luminescence appeared a t 0-05 mm. in the positive region and a ttain ed a m axim um in ten sity a t 140° and 0-3 mm.
Above 1 mm. pressure a continuous spectrum was obtained, th e in ten sity of th e m ercury arc lines (X 5461, 4358, and 4047) being greater th a n th a t obtained by electrical excitation alone. Since th e in ten sity of th e fluorescence is proportional to th a t of th e activating light, it is concluded th a t a single stage of absorption precedes emission, an d th a t th e oscillat
ing discharge produces a non-uniform distribution of the atom s in the 23P 012 state, followed b y passage to the 23iS'j sta te consequent on absorption of certain incident radiations. The fluorescence results from th e re tu rn to th e norm al state. J . Gr a n t.
F lu orescen ce of m e rc u ry v a p o u r u n d e r a to m ic a n d m o le c u la r a b so rp tio n . (Lo r d) Ra y l e i g h
(N ature, 1931, 127, 10).—M ercury vapour gives the green fluorescence when excited b y wave-lengths as long as 3450 A. The discontinuous n atu re of the fluorescence excited by wave-lengths near th e reson
ance line 2537 A. is confirmed b y th e fact th a t the addition of hydrogen suppresses th e fluorescence arising from atom ic absorption, leaving th e molecular effect practically unaltered. L . S. Th e o b a l d.
Z eem an effect in th e h y perfin e s tr u c tu r e of th e th a lliu m line, 3775 A. E. B a c k and J . Wu l f f
(Z. Physik, 1930, 66, 31—4S).—The Zeem an effect of th is particularly simple line was observed for m agnetic fields of 17,050, 29,700, and 43,350 gauss w ith a 6-3-metre Rowland grating. The results are discussed in relation to Goudsm it and B acker’s theory (see th is vol., 135) of th e position and in ten sity of th e Zeeman com ponents. The presence of ordinarily forbidden transitions predicted b y this theory was veri
fied. Generally, th e experim ental results are in good agreem ent w ith theo ry if a nuclear spin m om entum of 7 u n it is assum ed. A. B. D. C a s s i e .
H yperfine s tr u c tu r e of b ism u th . P . Ze e m a n, E . Ba c k, and S. Go u d s m it (Z. Physik, 1930, 66, 1— 12).—New experim ents on th e hyperfine structure of th e bism uth arc lines, and then- Zeeman effect, are described. The results complete earlier work, w ith ou t changing th e theoretical deductions. A scheme of term levels is given. The excited levels have no t been sufficiently investigated to give more th a n then- to ta l and inner q uantum num bers. The coefficient of proportionality in a Lande separation form ula for interaction of nuclear spin, an d resu ltan t electronic
1 3 8 B R IT IS H C H E M IC A L A B ST R A C TS.— A .
angular m om entum of the o u ter shell, is given for th e different levels. In ten sity formulae for th e hyper- fine stru ctu re are also given. T he different arc lines, th eir hyperfine structure, and Zeeman com ponents are discussed in detail. An appendix by Ba c k and J . W u l f f shows photographs of th e 10 hyperfine Zeeman com ponents of bism uth, agreeing w ith th e assigned nuclear spin of 4£ units. A concave grating and a Hilger echelon were used to o btain th e ph o to
graphs. A. B. D. Ca s s i e.
R e fle x io n of lo n g -w a v e-le n g th X -ra y s . J . Th i b a u d (J. Phys. R adium , 1930, [vii], 1, 404).—
A discussion of the results of Valouch (cf. A., 1930, 1229) in relation to th e au th o r’s formula! (cf. ibid.,
512). N. M. Bl i g h.
F in e s t r u c t u r e of c e r ta in X -ra y e m is s io n lin e s . J . Va l a s e k (Physical R ev., 1930, [ii], 3 6 , 1523—
1530).—The K a lines of iron, cobalt, nickel, copper, m olybdenum , and silver were investigated, using tw o specially constructed single-crystal spectrom eters.
The fine stru ctu re reported by Davis an d Pui-ks (cf.
A., 192S, 451, 819) was n o t confirmed. Photom icro
graphic curves from plates tak en in the first and second order are reproduced, and w idths of oq fines an d the
¡1, fine of m olybdenum are tabulated.
N. M. Bl i g h. S c a tt e r in g p o w e r f o r X -ra y s of th e a to m s in m a g n e s iu m o x id e a n d s o d iu m flu o rid e . R , W . G.
Wy c k o f f and A. H . Ar m s t r o n g (Z. ICrist., 1930, 72, 433—4 4 1 ; Chem. Z entr., 1930, ii, 353).—The intensities of th e principal fines, using M oKa radiation, have been m easured. T he results for sodium fluoride agree with those of H avighurst. A. A. El d r i d g e.
W a v e -le n g th of X -ra y s . T. H . L a b y and R . B i n g h a m (N ature, 1930, 126, 915—910).—Using R ow land’s m ethod of coincidence of lines, th e K fine of carbon has been photographed over a range of n \ from 0 to 810
A.
B y com parison w ith th e L x and L I fines of copper th e w ave-lengths 44-7 and 44-8A.
have been obtained for th e carbon fine relative to 13-32A.
for the copper Ltx line. T he alum inium Kxpxo fine is 8-315A.
relative to copper Kxp/..,1-5392
A.
L. S. T h e o b a l d .S a te llite s of th e Iip 1 lin e of e le m e n ts f r o m i r o n to z in c . S. Ka w a t a (Mem. Coll. Sci. K yoto, 1930, A , 1 3 , 383—387).—The wave-lengths of tw o new satellites discovered on th e short w ave-length sides of K $ 1 an d K$., of each of th e elements from iron to zinc have been determ ined. W . G o o d .
A b s o r p tio n f o r m u la of X -ra y s . I I . M. I s h i n o and S. Iv a w a t a (Mem. Coll. Sci. K yoto, 1930, A, 1 3 , 375—381; cf. A., 1928, 212).—The results of experi
m ental determ ination of th e absorption coefficients of elem ents and aqueous salt solutions for various wave-lengths are given. I t is shown th a t th e tru e atom ic absorption coefficient is no t proportional to w Z i, where p and q are constants independent of th e wave-length, X, and th e atom ic num ber, Z.
■j) and q are nearly equal to b u t less th a n 3 and 4,
respectively. W. G o o d .
X -R a y a b s o r p tio n i n g a s e s . W . W. Co l v e r t
(Physical R ev., 1930, [ii], 36, 1619— 1624).—Using double reflexion of X -ray spectral fines from a
platinum -surfaced m irror and a calcite cry stal in order to increase hom ogeneity of th e beam , absorp
tio n m easurem ents were m ade with neon, sulphur dioxide, chlorine, and argon, and m ass absorption coefficients for the range of rad iation wave-lengths 0-496—2-288 A. are tab u lated . N . M. Bl i g h.
G lo w d is c h a r g e a t t h e a c tiv e e le c tro d e of a n e le c tro ly tic re c tifie r. J . S. Fo r r e s t (Phil. Mag., 1930, [vii], 1 0 , 1003— 1014).—The lum inosity ap p ear
ing on th e surface of th e active electrode of a recti
fying cell was investigated, using cells with active electrodes of alum inium , tan talu m , and tungsten, th ro ug h observations on th e P .D .-c u rre n t curves, thickness, and pressure of th e gas layer on the electrode surface, spectrum of th e glow, influence of m agnetic fields, an d comparison w ith th e cathode glow. Evidence suggests th a t th e glow is produced by th e ionisation of oxygen molecules b y collision w ith electrons, and th e subsequent recom bination of th e electrons w ith th e ionised molecules.
N. M. Bl i g h.
P h o to - io n is a tio n of c æ s iu m v a p o u r b y a b s o r p t i o n b e tw e e n th e s e r ie s lin e s . C. Bo e c k n e r and
F . L. Mo h l e r (Bur. S tand. J . Res., 1930, 5, 831—
842).—The photo-ionisation of çæsium produced by a small continuous absorption between th e series fines has been m easured b y th e space-charge m ethod.
T he relative.sensitivity, i(X)//(3200 A.), increases w ith th e square ro o t of th e pressure w ithin th e range 3750—3250 A. The values are alm ost independent of th e tem perature on th e red side of 3500 A., b u t on th e other side th e effect is reduced to ab o u t half b y a rise in tem p erature of 70°. These results indicate t h a t absorption between th e fines is of m olecular origin and th a t th e w ork of dissociation of Cs2 is ab o u t 0-26 electron vo lt (cf. A., 1930, 1079).
A. R . Po w e l l.
P h o to - e le c tr ic p r o c e s s e s . M. St o b b e (Ann.
Pliysik, 1930, [v], 7 , 661— 715).—A theoretical con
trib u tio n to th e q u an tu m mechanics of photo-electric
processes. W. Go o d.
P h o to - e le c tr ic effec t of a l u m i n iu m a n d a lu m i n i u m a m a lg a m s . H . Ge r d i n g (Z. physikal.
Chem., 1930, B , 1 1 , 1—37).—The photo-electric cu rren t from alum inium and its am algam s with 0-06, 0-26, and 0-38% H g has been studied in relation to th e wave-length of th e incident fight, th e tim e of exposure, and th e condition of th e illum inated surface.
The quo tient c/7 (electron em ission/intensity of light) in a vacuum is increased by scraping th e surface, especially for wave-lengths near th e photo-electric threshold, which is itself displaced tow ards th e red.
A scraped surface becomes fatigued in a vacuum , an d more rapidly after co ntact w ith air, th e pho to electric threshold in this case being displaced tow ards th e ultra-violet. The m axim um values of c/7 and of th e photo-electric threshold obtained b y continued scraping in a vacuum are least for p u re alum inium , slightly higher for th e 0-06%, and highest for the 0-26% and 0-38% amalgams. This resu lt affords sup
p o rt to th e view th a t passivity is prim arily a ttrib u t
able to differences in th e m etal itself. T he fatigue observed on keeping is due to adsorption of air, and is caused b y th e negative co ntact p otential acquired
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 IS T R Y . 139
by the air film, acting as a retarding p o tential for the expelled electrons, increasing th e work required for their expulsion. F . L. Us h e r,
P h o to -e le c tric e m issio n fro m th in film s of cæ siu m . L. R . Ro l l e r (Physical R ev., 1930, [ii], 36, 1639— 1647; cf. Campbell, A., 1928, 1297;
Zworykin, A., 1929, 1262; Olpin, A., 1930, 1230).—
The photo-electric properties and m ethods of p re
paring thin films of cæsium were investigated. In one ty p e a th in film of cæsium is adsorbed on a 'thin' lajæ r of oxygen previously adsorbed on th e silvered bulb of th e photo-electric cell. In th e other, a thin film of cæsium is adsorbed on a layer .of suboxides of cæsium obtained b y coating a cathode w ith metallic cæsium and adm itting traces of oxygen ; th e photo
electric curren t was recorded sim ultaneously. Results show th a t th e m ost sensitive surfaces are obtained when a suboxide, ra th e r th a n th e norm al oxide Cs20 , has been formed, and th a t th eir properties are duo to th e arrangem ent of molecules very n ear th e surface.
N f M. Bl i g i i.
R a d io -fre q u e n c y p ro p e rtie s of io n ised air.
E. V. Ap p l e t o n and E. C. Ch i l d s (Phil. Mag., 1930, [vii], 10, 969—994).—The m easurem ent of th e di
electric constant of a conducting ionised m edium is examined m athem atically and an investigation, sug
gested thereby, of th e high-frequency behaviour of ionised gases by m easuring th e dielectric constant of air is described. As ionisation increased the dielectric constant reached a m inim um value from which it increased to greater th a n unity. This divergence from theoretical prediction was found to be due to the form ation of ionic sheaths round th e electrodes, thus increasing the capacity of th e condenser. The variation of th e thickness of th e sheaths w ith the potential across them was examined by a wireless method, and gave results in agreem ent w ith the theory of collectors due to Langm uir and M ott- Smith. The influence of an imposed m agnetic field on th e radio-frequency properties of ionised air was studied, and th e existence of a predicted inverse Zeeman effect confirmed. Pronounced absorption occurs a t a critical frequency corresponding with a particular value of the imposed field ; th e ratio of the two last-nam ed confirms th e electronic n ature of the electric carriers, supporting L arm or’s theory of the refractive deviation of wireless waves in the upper atm osphere by free electrons.
N. M. Bligh. In te rn a l co n v e rsio n of n u c le a r en erg y . H.
Ca s i m i r (N ature, 1930, 126, 953—954).—An expres
sion for the coefficient of internal photo-effect has been deduced using D irac’s equation, and a com
parison of the calculated photo-effects w ith the internal conversions m easured by Ellis and Aston for radium -C (A., 1930, 1339) shows th a t th e num ber of ejected electrons is larger th a n would be expected from th e internal photo-effect. This shows th a t for the hard y-rays of radium -C the ejection of atomic electrons is due m ainly to interaction in the nuclear
region. L. S. Th e o b a l d.
E ffective c ro s s -se c tio n of k ry p to n to w a rd s slow e lectro n s. J . Ho l t s m a r k (Z. Physik, 1930, 66, 49—59).—The d a ta of H artree for the atomic
field of krypton, duly corrected for polarisation energy, have been used to com pute th e effective cross-section of krypton molecules tow ards electrons of energy from 0 to 7 volt~J. The agreem ent between th e resulting values and th e experim ental results of R am sauer and K ollath is satisfactory.
R. W. Lu n t.
L ib e ra tio n of e le c tro n s fro m a m e ta l su rface b y p o sitiv e ion s. II. F . M. Pe n n i n g (Proc. K.
Akad. W etensch. A m sterdam , 1930, 33, 841—857;
cf. A., 1928, 681).—M easurem ents have been m ade of y, th e average num ber of electrons liberated from a m etal surface by each positive ion, using positive ions of neon a t different velocities. W hen extrapolated to zero velocity, th e result y0= 0-05 is obtained, indicating th a t positive neon ions of zero velocity can liberate electrons. The experim ents 'were conducted in such a w ay th a t m etastable atom s, high-velocity n eu tral atom s, and light q u an ta could no t strike the collecting electrodes. A t higher velocities the value of y depends on th e m aterial surface of the cathode and on th e presence of im purities. E. S. He d g e s.
C h a ra c te ris tic velocities of e le c tro n s s c a tte re d fro m m e ta llic su rfa c es. G. Be r n a r d i n i (A tti R . Accad. Lincei, 1930, [vi], 11, 1096— 1099).—
Electrons having velocities of 34— 50 volts em itted from a tu n gsten -tho riu m filam ent were allowed to impinge on brass an d zinc surfaces, and the m agnetic spectra of the resulting scattered electrons were photographed. The lines in these spectra correspond w ith characteristic electron velocities, b u t it is no t certain w hether th ey are really characteristic of the m etallic surface, or are due to adsorbed gas.
O. J . Wa l k e r.
F re e e le c tro n s in m e ta ls a n d th e ro le of reflex
io n s a c c o rd in g to B ra g g . L. Br i l l o u i n (J. Phys.
R adium , 1930, [vii], 1, 377— 400).— Theoretical. An investigation m ade of th e n atu re of electron waves in a m etal, and th e conditions for selective reflexion analogous to those of B ragg for M-rays, using the Schrödinger pertu rb atio n m ethod, leads to d a ta on th e m ovem ent of free eleotrons in th e crystal lattice in agreem ent w ith th a t of Bloch (cf. A., 1929, 247 ; Peierls, A., 1930, 281). The m ethod is extended to the electronic m om ents, and leads to a series of surfaces, forming by their interlacing a lattice divid
ing th e electron waves into zones, the separating planes corresponding w ith B ragg’s conditions. Each zone corresponds w ith th e waves obtained b y the coupling of those of a certain qu antu m level of the ion; th e condition for th e num bering of th e waves gives an expression for th e wave-length, and agrees w ith th e app arent num bering obtained by considering th e ions as p o in t charges. The form ula for the electron energy is analogous to th a t of th e free electrons of space, b u t involves an app aren t mass which m ay become negative, and differs from th e tru e mass. The problem is thus analogous to the num ber
ing of th e external orbits of complex atom s involving th e tru e and the ap p aren t quantum num ber of th e R ydberg formula. Results deduced for a num ber of m etals are tab ulated. N. M. Bl i g h.
C a p tu re of e le c tro n s b y ions. G. Wa t a g h i n
(A tti R. Accad. Lincei, 1930, [vi], 11, 993— 997).—
1 4 0 B R IT IS H C H E M IC A L A B ST R A C TS. A .
The probability of th e transition of an ion from its free sta te to th e n th quantum sta te b y th e capture of electrons has been calculated from th e principles of wave mechanics. The resu lt affords an explanation of th e experim ents of Davis and B arnes (cf. A., 1929,
971). F . G. Tr y h o r n.
E n e rg y lo sse s of e le c tro n s in c a rb o n m o n ox ide a n d c a rb o n dioxide. E . Ru d b e r g (Proc. B oy.
Soc., 1930, A, 130, 1S2— 196).—An extension of previous work (this vol., 12). In th e case of carbon monoxide, th e pressures used ranged from 7 to 62 X 10"3 mm., and for carbon dioxide from 15 to 24 X 10“3 mm. The energy distribution of the electrons afte r passing through th e gases showed a num ber of well-marked m axim a which are characteristic of the energy levels of th e molecules under investigation.
The various m axim a for carbon monoxide are corre
lated w ith transitions from th e norm al to excited states of th e molecule, know n from th e analysis of the band spectra of th e n eutral or singly-ionised carbon monoxide molecules. I n cases where a m axim um is attrib u te d to a single electronic level, an exam ination of th e potential energy curves for th e molecule shows th a t th e position of th e m axim um in respect to th e different possible vibrational levels is in excellent agreem ent w ith the F ranck-C ondon principle (A., 1927, 89). No evidence of th e ionisation of soft X -ray levels has been found for either of th e
gases. L. L. Be r c u m s h a w.
E m is s io n of e le c tro n s u n d e r th e influence of c h e m ic a l a c tio n a t lo w e r g a s p re s s u re s . 0 . W.
Ri c h a r d s o n and L. G . Gr i m m e t t (Proc. R oy. Soc., 1930, A, 130, 217—238; cf. B rotherton, A., i924, ii, 377; R ichardson an d B rotherton, A., 1927, 713).—
D etails are given of a m ethod w hereby controllable and m easurable pressures of carbonyl chloride can be obtained down to 10~5 mm. of m ercury. The emission of electrons from an alloy of sodium and potassium (NaK) in this gas has been exam ined down to m easured pressures of 10-5 and to ex trapolated pressures of 5 x 1 0 “' mm. under various conditions.
'.Che results show th a t the satu ratio n current i0 in creases continuously w ith th e p artia l pressure p of the gas from zero u p to a critical value in th e neigh
bourhood of p = 10“3 mm. This critical value depends on th e ra te of flow of th e alloy, being sm aller th e slower are th e drops. The m axim um to tal charge which can be em itted b y any one drop appears to be a fixed qu an tity , proportional to th e size of the drop.
Evidence is adduced to show th a t the experim entally determ ined velocity distribution function among th e electrons approaches a lim it as the pressure is reduced.
L . L. Be r c u m s h a w.
S e c o n d a ry ele c tro n ic e m issio n s fro m m e ta l foils a n d a n im a l tis s u e s. W . V. Ma y n e o r d
(Proc. R oy. Soc., 1930, A, 130, 63—SO).—The relative intensities of beams of X- and y-radiation of different wave-lengths, when m easured by th e ionisation cham ber m ethod, depend on th e m aterial of the cham ber. A m athem atical theory is developed which shows th a t, neglecting certain secondary factors, small ionisation cham bers artificially m ade sensitive b y th e insertion of foils of different elements show a m axim um sensitivity in th e region of medium w ave
lengths, when com pared w ith an air cham ber. This is confirmed b y experim ent. An ionisation cham ber for th e m easurem ent of th e in tensity of y-rays is described; it was found th a t th e relative intensities of p rim ary and secondary scattered beams of rays h ad different values according to th e m aterials com posing th e chamber. A region of m axim um sensitivity was also observed w ith ionisation cham bers con
taining anim al tissues. The significance of these observations is discussed. L. L. Bi r c u m s h a w.
S p ecific c h a r g e of t h e e le c tro n . F. Ki r c h n e r
(Physikal. Z., 1930, 3 1 , 1073— 1075).—The use of an oscillating circuit for determ ination of th e specific charge of th e electron (cf. ibid., 1929, 3 0 , 773) has been considerably im proved, and gives for e/m0 th e value l-76024;0-0025 e.m .u. This agrees w ith th e spectroscopic value, b u t deviates unaccountably from th e cathode ra y value. A. B. D. Ca s s i e.
A p p licatio n of e le c tro n in te rfe re n c e to s tr u c tu r e an aly sis. E . R u p p (Physikal. Z ., 1930, 3 1 , 1076— 1078).—Thom son’s m ethod for determ ination of th e stru ctu re of a surface layer b y reflexion of electrons of approxim ately 30 kilovolts (cf. A., 1930, 1082) is inapplicable to very th in layers. Electrons of 100 volts energy p en etrate approxim ately 10 crystal planes, an d m ay therefore be applied to th in layers. Reflexion from (100) planes of copper afte r various h ea t trea tm e n ts was investigated by p lotting intensity against electron velocity for a fixed angle of
incidence. A. B. D. Ca s s i e.
M ag n etic a n a ly sis of n eg ativ e io n s in m e rc u ry v a p o u r. W. M. Ni e l s e n (Proc. N at. Acad. Sci., 1930, 1 6 , 721—727).—Ions produced b y a discharge in m ercury vapour a t a pressure of th e order of 10“4 mm. have been analysed m agnetically to determ ine th e n atu re of th e negative ions. The experim ental m ethod consisted in sweeping o u t of th e p a th of a beam of electrons projected in th e m ercury vapour parallel to a m agnetic field either positive or negative ions b y m eans of a crossed electric field. The separ
ated ions are fu rth e r accelerated in a second electric field. Curves are given showing th e ra tio of ion to to tal electron cu rren t against m/e. Hg~, CO“, and C~
are identified. A t m/e equal to 19 and 60 two peaks (not identifiable) are observed. All the peak m axim a appear in th e analysis of th e positive ions. The app aratu s did n o t give tru stw o rth y results a t higher pressures because of the form ation of a positive space charge in th e electron beam. W. Go o d.
P re s s u r e a n d hig h -v elo city v a p o u r jets a t c a th o d s of a m e r c u ry v a c u u m a rc . E. Ko b e l
(Physical R ev., 1930, [ii], 3 6 , 1636— 1638).—M easure
m ents on a m ercury arc and fixed cathode spot gave th e value 0-017 x 10“3 g. p er am p. sec. for th e am ount of m ercury vaporisation, and 16—43 X 10® cm. p er sec.
for th e vapour velocity, in good agreem ent w ith the results of Tanberg (cf. A., 1930, 832) for th e v ap o r
isation of copper from th e cathode of a copper arc.
N. M. Bl i g h.
D is trib u tio n of ra y s in m o le c u la r s tre a m s . P . Cl a u s i n g (Z. Physik, 1930, 66, 471—476).—
Formulas are deduced for th e space distribution of molecules stream ing through a short tub e into a
G E N E R A L , P H Y S IC A L , AND IN O R G A N IC C H E M IST R Y . 1 4 1
vessel th e radius of which- equals its length, the length being is small com pared w ith th e molecular free path. If diffuse scattering by th e walls of the entrance tu b e governs this space distribution, large departures from th e cosine law should occur. This is in contradiction w ith M ayer’s experim ental results (ibid., 192D, 58, 373). ' A. B. D. Ca s s i e.
R ela tio n sh ip b etw een e le c tro n d iffraction m a x im a a n d th e e m issio n of so ft A'-rays.
H . W . B. Sk i n n e r (Naturwiss., 1930, 18, 1097—
1098).—An explanation of th e experim ental results of R upp (A., 1930,1493) is offered. W . R . An g u s.
In tro d u c tio n of exch an g e in to th e s ta tis tic s of an electron ic g as. L. Go l d s t e i n (Compt. rend., 1930, 191, 1306—1308).—The application of the statistical m ethod (Dirac) to th e atom is based on the analogy betw een atom ic electrons an d a degener
ate electronic gas. F erm i’s formulas m ust be re
vised to include th e energy of electronic exchange, which, together w ith th e kinetic and potential energies, makes up th e to tal energy of a system of electrons.
I t is shown m athem atically th a t th e energy of agit
ation of an electronic gas is m ade up of th e energy of kinetic agitation and th e energy of exchange
agitation. J . Gr a n t.
E q u a tio n s of e le c tro n th e o ry a n d D irac wave m echanics. N. R . Se n (Z. Physik, 1930, 66, 122—
128).—M athem atical. ' A. B. D. Ca s s i e.
D irac th e o ry of p ro to n s a n d electro n s. G. I.
Po k r o v s k i (Z. Physik, 1930, 66, 129—136).—Theor
etical. Some app arent difficulties of D irac’s theory are explained, an d an upper lim it for th e energy of one quantu m is deduced. A nother result of the theory is th a t all m otion is quantised, so th a t two successive transitions m ust have a definite time interval betw een them . A. B. D. Ca s s i e.
G ra p h ic a l calc u la tio n of th e m a g n itu d e s in volved in a n ele c tro n in m o tio n . G . Fo u r n i e r
(Compt. rend., 1930, 191, 1302—1304).—I t is shown th a t th e relations betw een th e lengths of th e lines and angles involved in th e construction of a trigono
metrical circle correspond w ith th e m agnitudes of an electron in m otion, e.g., the ratio of electronic velocity to th a t of light, th e Lorentz concentration an d time- transform ation factors an d the factors required for the calculation of th e emission potential and th e Broglie wave-length, and th e product of I I and the radius of a circle described by an electron in a field
of H gauss. J . Gr a n t.
P ro p e rtie s of n u c le a r electro n s. J . K u d a r
(Physikal. Z., 1931, 32, 34—37).—Theoretical.
A. J . Me e. M e a su re m e n t of cro ss-se c tio n of n o n -in e rt gas m olecules fo r slo w e lectro n s. E . Br u c h e (Ami.
Physik, 1930, [v], 7, 579—587)—Polemical against Brose and Saaym an (A., 1930, 1084). A. J . Me e.
M e a su re m e n t of c ro ss-se c tio n of n o n -in ert g a s m olecules. H . L. Br o s e a n d E. H . Sa a y m a n
(Aim. Physik, 1930, [v], 7, 588—595).—A reply to Bruche (see above). A. J . Me e.
M e a su re m e n t of c ro ss-se c tio n of n o n -in e rt g as m olecules. E. Br u c h e (Ann. Physik, 1930, [v],
7, 596—600).—A reply to Brose and Saaym an (see
above). A. J . Me e.
M e a s u re m e n t of m a g n e tic su scep tib ilities of g ases. H . Bu c h n e r (Ann. Physik, 1930, [v], 7,716—
730).—A m ethod (Gouy m ethod w ith torsion balance) for th e m easurem ent of m agnetic susceptibilities of gases is describ ed; it gave for carbon dioxide a value, (—8 -6 + 0 -4 )x l0 ~ 10, in good agreem ent w ith existing d ata. Between 0 and 600 mm. pressure the volume susceptibility is found to be directly propor
tional to th e pressure; sim ilarly for m ixtures of carbon dioxide and oxygen (0-125—0-430% 0 2), the m ixture law being confirmed. The Glaser pressure anom aly is apparently due to adsorption effects.
U nder certain conditions Glaser curves could be obtained in experim ents w ith undried oxygen and w ith undried carbon dioxide. A critical review of existing researches in this field is m ade and it is con
cluded th a t th e mass susceptibilities of carbon dioxide and m ixtures of it w ith oxygen are independent of the
pressure. W. Go o d.
U n it of at. w t. F . W. As t o n (Nature, 1930,126, 953).—A ttention is directed to the need for a recon
sideration of the scale of a t. w ts. arising from the com plexity of oxygen. L. S. Th e o b a l d.
A t. w t. of p o ta s s iu m fro m p la n t ash . H . H.
Lo w r y (J. Amer. Chem. Soc., 1930, 52, 4332— 4333).
—D eterm inations of th e potassium -chlorine ratio w ith potassium from cotton ash and w heat flour ash yield th e at. w t. 39-111+0-013 and 39-091+0-016 (01=35-457), respectively, which are in good agree
m ent w ith accopted values for potassium . This is evidence th a t p lan t cells do n o t absorb selectively the radioactive isotope of potassium from th e normal m ixture of isotopes (cf. Zwaardemaker, A., 1926, 554;
Loring and Druce, Chem. News, 1930, 140, 34).
J . G . A. Gr i f f i t h s.
R evision of th e at. w t. of th a lliu m . A nalysis of th a llo u s b ro m id e . 0 . H o n i g s c h m i d and H.
St r i e b e l (Z. anorg. Chem., 1930, 194, 293—298).—
Analysis of thallous bromide by precipitation of silver bromide yields for th e at. w t. of thallium 204-390+
0-008, in agreem ent with th a t obtained previously by analysis of th e chloride. The solubility of thallous bromide in w ater a t 18°, 25-68°, and 68-5° is 423-3, 579, an d 2520 mg. per litre, respectively.
H. F . Gi l l b e.
S e p a ra tio n of th e iso top es of b ro m in e . At. w t.
of b ro m in e fro m th e ra tio A g : A gB r. P. Ha r- t e c k and H . St r i e b e l (Z. anorg. Chem., 1930, 194, 299—304).—The theory of the separation of isotopes by fractional sublim ation is described. The m ost volatile fraction obtained by fractionally subliming brom ine in a current of hydrogen a t —18-5°, —25°, and —36° had an at. wt., determ ined from th e ratio Ag : AgBr, of 79-916+0-001, which is identical with th a t of ordinary bromine. The failure to produce any separation is ascribed to th e fact th a t in a m ixture of isotopes th e vibrational energies of the individual atom s an d molecules are so inter-related th a t th e difference of th e vibrational energies of two isotopes is less for a m ixture th an for th e separated isotopes, and th e m agnitude of th e effect is therefore reduced to less th a n the experim ental error. H. F . Gi l l b e,
142 B R IT IS H C H EM IC A L A B ST R A C TS.— A .
R e la tio n b etw e en th e e m issio n of lo n g -ra n g e a-ra y s a n d y -ray s. ( Mm e. ) P. Cu r i e (Compt.
rend., 1930, 191, 1055— 1058).—A n extension and comparison w ith experim ental results of Gamow’s theory, from which it is concluded th a t in th e cases of radium -C ' an d thorium -C ' Gamow’s form ula gives approxim ate results. J . Gr a n t.
F o rm a tio n of long -liv ed active m o lecu les in h y d ro g e n su b je c ted to th e a c tio n of a-p articles fro m ra d o n . E . C. Tr u e s d a l e (J. P hysical Chem., 1930, 34, 2472—2478).—The work of D uane and W endt (Physical R ev., 1917, 10, 117) has been re peated using certain refinements. H ydrogen sulphide could be detected in small am ounts only w hen sulphur was present in th e reaction sphere surrounding th e radon, and no evidence of th e existence of long-lived active hydrogen or of triatom ic hydrogen was obtained.
L. S. Th e o b a l d. S c a t t e r i n g o f h a r d y - r a y s . C. Y . Ch a o (Physical R ev., 1930, [ii], 36, 1519— 1522; cf. A., 1930, 1086).—
In order to investigate th e deviation of th e absorption coefficient for heavy elements from th a t predicted by th e Ivlein-N ishina form ula m easurem ents were m ade on the scattering of y-rays from thorium -C by. alum in
ium and lead. F or lead additional scattered rays were observed; these are considered to have a nuclear origin, since th eir wave-length and space distribution are inconsistent w ith an extra-nuclear scatterer.
N . M. Bl i g h.
S c a tte rin g o f h a r d y-rays. L. La n d a u (N atur- wiss., 1930, 18, 1112).— Polem ical against Beck (A.,
1930, 1496). W. R . An g u s.
A rtific ia l e x c ita tio n of n u c le a r y-ray s. W.
Bo t h e and H . Be c k e r (Z. Physik, 1930, 6 6 , 289—
306).—An apparatu s for th e efficient use of a-rays from a polonium source in exciting nuclear levels in non-radioactive substances is described. N itrogen, carbon, oxygen, neon, calcium, and silver showed no secondary nuclear emission w ithin th e lim its of experi
m ental error; lithium , beryllium , boron, fluorine, magnesium, and alum inium showed emission, beryll
ium emission being m uch more intense th a n the others.
Absorption m easurem ents of this emission from boron and beryllium showed it to be of approxim ately th e sam e wave-length as th e hardest y-radiation from rad io
active substances, b u t th e hard secondary radiation from lead (cf. A., 1922, ii, 13) could n o t be detected.
A curve showing th e approxim ate variation of intensity of th e secondary radiation from beryllium w ith th e energy of the exciting a-particles was obtained, b u t is n o t sufficiently accurate for theoretical interpretation.
Possible theoretical interpretations of th e results, on Gamow’s model of th e nucleus, are discussed.
A. B. D. Ca s s i e.
A y -ra d ia tio n fro m p o lo n iu m . W . Bo t h e and H . Be c k e r (Z. Physik, 1930, 6 6 , 307—310).—E xperi
m ents described (cf. preceding abstract) showed th a t polonium em its a hith erto unobserved hard y-radia
tion. One quantu m of this radiation is em itted for every 105 atom s disintegrated, and it is therefore probably due to excitation of polonium nuclei by a-particles em itted by th e disintegrating atoms.
A. B. D. Ca s s i e.
A tte m p ts to fin d a s ta b le iso to p e of p o lo n iu m . G. v o n H e v e s y and A. Gu e n t h e r (Z. anorg. Chem., 1930, 194, 162— 178).— The electrochemical b e
haviour of polonium has been investigated and th e b est conditions for its electrolytic isolation have been determ ined. The p n of the electrolyte is of im p o rt
ance; in presence of bism uth th e acid concentration should be between N and 0-33A7, as a t higher concen
tratio n s polonium is redissolved and a t lower con
centrations bism uth separates as a result of h yd ro lysis. I n presence of tellurium electrolysis w ith a cu rren t density of 10-3 am p. per cm.2 from a A’-acid solution yields a deposit containing only traces of tellu riu m ; gold considerably decreases th e yield.
The best yield and th e p urest product are obtained by electrolysis w ith a P .D . of 1 v o lt an d a cu rren t density of 1 — lO x lO -4 am p. p er cm .2, using a ro tatin g m olybdenum cathode. Polonium , together
■with tellurium , m ay be separated from bism uth by precipitation with a reducing agent such as stannous chloride, and from tellurium by precipitation of the hydroxide. B y application of these reactions large quantities of th e m inerals hessite, calaverite,nagyagite, bism uth telluride, and bism uth glance, and of metallic bism uth, have been worked up w ith addition and final rc-separation of polonium as a radioactive indicator, in order to separate a stable isotope of polonium, b u t A -ray analysis of th e final precipitate shows th a t an y such substance cann ot be present in th e m inerals to a greater ex ten t th a n 10-11 g. p er g.
H . F . Gi l l b e.
D e te rm in a tio n of r a d iu m b y th e e m a n a tio n m e th o d . R . G. F u l t o n (J. Assoc. Off. Agric.
Chem., 1930, 13, 497—503).—The Boltwood m ethod (A., 1904, ii, 666) as modified b y Sale (J. Assoc. Off.
Agric. Chem., 1925, 8, 531) was used in th e exam in
atio n of a radioactive w ater sample, a water-soluble salt, and a refractory m aterial. A few m inor m anipul
ative details were modified. T he results were satis
factory and were checked against th e m ethods of iSchlundt and Moore (A., 1905, ii, 368) and of B arker (A., 1918, ii, 371). Cyrtolite ore also was examined by the procedure prescribed for a refractory substance with satisfactory results. H . J . Do w d e n.
C an le a d be m a d e ra d io a c tiv e ? G. Gu e b e n
(Ann. Soc. Sci. Bruxelles, 1930, 50, B , 117— 121).—
Experim ents have been conducted w ith lead of 99-95%
p u rity ; one specimen was w rapped in black paper an d shielded from pen etrating radiation, a second specimen was exposed to sunlight for 7 m onths, a th ird was exposed to th e radiation from a mercury- vapour lam p for 5S0 hrs., a fourth was subjected to A -rays for 185 Ins., and a fifth was subm itted to radiations from radium em anation for 7 m onths.
None of th e lead specimens becam e radioactive after th e treatm en t. I t is concluded th a t th e radioactivity observed in leaden roofs is due no t to th e absorption of radiation, b u t to th e accum ulation of a radioactive deposit from th e atm osphere. E . S. H e d g e s.
M ode of w o rk in g of G eig er c o u n tin g c h a m b e rs.
C. Bo s c h and H . Kl o m p. (Naturwiss., 1930,18, 1098).
—Geiger counters w ith copper, silver, gold, iron, and zinc electrodes in helium were used. The presence of electronegative im purities prom oted th e counts.
