APR. 4, 1923 SCIENTIFIC NOTES AND NEWS 139 
Messrs. G. W. Vinat and G. N. Scuramm presented a paper on The 
tarnishing and detarnishing of silver. The paper, which was illustrated by 
lantern slides, was presented by Dr. Vinau and discussed by Messrs. PAULING, 
HawxswortH, Humpureys, LAMBERT, GisH, Hnyn, and SHowey. 
Author’s abstract: The tarnish observed on silver is ordinarily the sul- 
phide. It was found that hydrogen sulphide causes tarnishing of silver 
when moisture is present, and particularly when sulphur dioxide is also 
present. 
The electrolytic method for detarnishing silver is based upon the fact 
that the silver immersed in a solution of salt and soda and in contact with 
and electro-positive metal forms a cellin which the hydrogen passing to the 
silver reduces the sulphide, liberating hydrogen sulphide. The reduced 
silver is left upon the surface in the moss condition. 
The tarnishes formed a definite color scale which may be used to estimate 
the extent of the tarnish. The colors are as follows: Yellow, red, purple, 
blue, blue-green, gunmetal, black. 
Experiments were made to study the tarnishing of silver in solutions and 
gas atmospheres, and conditions for establishing a standard tarnish were 
determined. The thickness of the tarnish film was found to range from 
0.18 to 0.36 microns, which is about 2 per cent of the thickness of the silver 
plating. Sterling silver tarnishes more readily than pure silver. Tarnishing 
is accelerated by the presence of moisture, sulphur dioxide and certain films 
on the surface of the silver, such as alkali and soap films. The tarnishing of 
silver may be retarded by the action of several reagents. 
Comparisons between various electrolytic devices for detarnishing were 
made. ‘There is practically no loss of silver by the electrolytic method of 
cleaning, unless the moss silver is present in objectionable amounts. . Silver 
losses are appreciable when the cleaning is done by abrasives and cyanide 
solutions. The potential differences between the silver and the various 
metals used for the cleaner were determined. 
Adjournment at 10:01 P.M. was followed by a social hour. 
J. P. Aut, Recording Secretary. 
SCIENTIFIC NOTES AND NEWS 
At the Physics Club, Bureau of Standards, on February 26, Dr. W. F. 
Meccers spoke on Line structure wn complicated spectra. 
The subject was introduced by a general outline of the earlier known 
regularities in the spectra of the chemical elements beginning with the 
Balmer series of hydrogen and followed by the types of series found in the 
relatively simple spectra characteristic of the elements in the first three col- 
umns of the periodic classification. There are four general types of series, 
principal, sharp, diffuse, and fundamental, each of which may be represented 
by single, double, or triple spectral lines. Doublets, triplets, and more 
complex structures are explained as arising in a multiplicity of P, D, and F 
energy levels between which electron transitions take place. The S term 
is generally single. In addition, certain inter-combinations of these series 
may represent observed spectral lines. 
The quantum theory assigns azimuthal quantum numbers 1, 2, 3, and 4 
respectively to the four general types of series and restricts inter-combina- 
tions to those involving a change of only one unit in quantum number. 
The sum of azimuthal and radial quantum numbers determines the position 
(term number) of a line in a series. An “inner quantum number’’ is asso- 
