PR W. M. HICKS: A CRITICAL STUDY OF SPECTRAL SERIES. 



S, (o) VF(4). The possible errors of the latter, however, are so large that they 

 cannot be used to improve the values found from the direct lines. The limit 

 calculated from D( oo) of [II.] and D,, (2) is 18064-21, but there is some uncertainty 

 owing to the abnormality of D(2) as explained above under the dinrassinn of the 

 D series. The lines F t (3) and F, (4) give 6946*02 (73) for VF(3) and 444174 ('37) 

 for VF (4). 



In the case of In no ultra-red lines have been observed. In K.R.'s list there 

 appears a doublet X = 2720"10, 2565"59, which shows a separation 2213"32, the true 

 doublet separation being about 2212'38. Its relative position in tin- s|-.-tiuin 

 compared with that of Al and Tl point it out as the Ititz combination S( oo) VP, (3). 

 K.R. also give a line at X = 2666'33 or n = 3749377 (2'8l), which from its pnsitim, 

 might be S,(oo)-VF(3). If so, the value of VF(3) is 6960-99 (2'80) and clearly 

 in line with those of Al and Tl. We shall adopt it provisionally. K.R. mark all 

 these lines as doubtful, but the existence of the doublet separation points to their 

 real existence- as In lines. Collecting these give the following : 



Al. In. Tl. 



VF(3) . . G95573 + '80p + 6960'99 + 2-80p + 



Denom. . . 3'970842-228jJ-285 3'969340-801p-285 

 VF(4) . . 4445-12 + 3'90g + f 444174 + ' 



Denom... 4'967208-2177?-558 4'969095-207qr-559 



It is seen that Al and In may be the same within limits. In Tl the uncertainty in 

 D (2) referred to above is such as to raise the limit and by 19 '19 if the explanation 

 there given is correct. A rise of 10 would make the denominator for m = : 3 the 

 same as for Al and In. 



One of the most striking results of this discussion of the F series is the distinct 

 divergence in type between the spectra of the high melting-point elements and those 

 of the low melting point, and at the same time the close resemblance between the 

 individual elements in each division. So close indeed is the resemblance l*;tween all 

 the low melting-point elements of Groups II. and III. that the differences between 

 them appear to be almost wholly due to the difference of the limits, or the value of 

 VD (2) and the values of VF (3) are almost the same. To see how closely they agree 

 the denominators to four places of decimals are collected here, and for comparison 

 those of the alkalies. 



It is seen how closely the elements in each group agree in spite of a very wi 

 difference in atomic weight, and moreover the mantisase in all are very close 



