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Spectrophotoelectrical sensitivity of some halide salts of thallium, lead, and silver
248
U.S.
BUREAU OF STANDARDS NOTES.
[J. F. I.
Formula I is especially suited to long, thin coils, while 2 is better adapted to pancake coils or coils of nearly square crosssection. Either may be used, however, in any case, and thus a check on the numerical work is afforded. Where interpolation has to be made in the tables, a greater accuracy is obtained if in I we write K ' = K - k , and obtain from the tables the values of K and k separately. K is Nagaoka's constant, the value of K', which applies to a cylindrical current sheet or coil with c = o . Similarly, in the case of 2 it is more accurate to put P' = P / a n d to interpolate for P and f separately. P is the value of P' which applies to a disk coil of zero axial thickness, b = o, and is tabulated here from Spielrein's formula as a function of 2a _c Examples are given to illustrate the use of the tables and formulas in practical cases, and the application of the tables to the calculation of the mutual inductance of coils of rectangular cross-section is treated and illustrated and the necessary formulas developed. The formulas on which the tables are based are collected for reference in an appendix. S P E C T R O P H O T O E L E C T R I C A L S E N S I T I V I T Y OF SOME H A L I D E SALTS O F T H A L L I U M , L E A D , A N D SILVER." By W. W. Coblentz and J. F. Eckford.
[ABSTRACT.] THIS paper, considered in connection with previous publications (Sci. Papers, No. 446 and one, on press), completes a study of the effect of crystal structure, chemical constitution, and atomic weight upon spectrophotoelectrical sensitivity. It is shown that these factors have a definite effect upon the photoelectrical reaction just as previously they were found to have a specific effect upon absorption and reflection spectra. It was found that the spectrophotoelectrical reaction of the halide salts of thallium, lead, and silver is confined to a very narrow region of the violet end of the spectrum, being the narrowest and most sharply defined reaction spectra of all substances yet published, including the photoelectric gas-ionic reaction spectra of the alkali metals. "Scientific Papers, No. 456.
Feb., 1923.1
U.S.
BUREAU OF STANDARDS NOTES.
249
Data are given showing that increasing the atomic weight of the acid element in the salts of thallium shifts the maximum of the spectrophotoelectrical reaction towards the long wave-lengths. The maximum of the spectrophotoelectrical sensitivity of T1 CI is at o.365~; of T1 Br at o.413~ ; and of T1 I, at o-455~. The photoelectrical sensitivity curves of the halide salts of thallium have the outline of what appears to be the typical spectrophotoelectrical reaction curve, vi~., a high photoelectrical reaction on the short wave-length side of the maximum, and a very abrupt termination of the reaction on the long wave-length side of the maximum. Lowering the temperature of T1 I to --60 C. had no appreciable effect upon the position of the maximum of the spectrophotoelectrical reaction. Of the halide salts of lead, Pb C12, Pb Br2, and Pb I2, only the iodide was found to react photoelectrically. The spectrophotoelectrical sensitivity curve of lead iodide appears to be complex with an ill-defined maximum in the region of o.45~, and sharply defined maximum at o.52~. The halide salts of silver appear to be sensitive photoelectrically when melted into a vitreous or semi-vitreous mass. Silver chloride exhibited photoelectrical sensitivity in the region of o.38F, Silver bromide has a maximum at o.46~. The sensitivity curve of silver iodide appears to be wide and complex with maxima at about o.47~ and o.5o~ respectively. In connection with these silver halide salts, an examination of samples of silver nitrate and potassium nitrate showed no photoelectrical sensitivity. G A S E S IN M E T A L S : x. T H E D E T E R M I N A T I O N O F C O M B I N E D N I T R O G E N IN I R O N A N D S T E E L A N D T H E C H A N G E IN F O R M O F N I T R O G E N BY H E A T T R E A T M E N T . 7 By Louis Jordan and F. E. Swindells.
[ABSTRACT.]
THE only form of nitrogen determined in iron or steel by the Allen or acid-solution method is that present as combined nitrogen, probably existing as nitrides of iron, or of such minor constituents as manganese, or aluminum. The solution of the metal sample for nitrogen analysis is made in hydrochloric acid of sp. gr. I.I I. 7Scientific Papers, No. 457. VOL. t95, No. 1166--18
U.S.
BUREAU OF STANDARDS NOTES.
[J. F. I.
Formula I is especially suited to long, thin coils, while 2 is better adapted to pancake coils or coils of nearly square crosssection. Either may be used, however, in any case, and thus a check on the numerical work is afforded. Where interpolation has to be made in the tables, a greater accuracy is obtained if in I we write K ' = K - k , and obtain from the tables the values of K and k separately. K is Nagaoka's constant, the value of K', which applies to a cylindrical current sheet or coil with c = o . Similarly, in the case of 2 it is more accurate to put P' = P / a n d to interpolate for P and f separately. P is the value of P' which applies to a disk coil of zero axial thickness, b = o, and is tabulated here from Spielrein's formula as a function of 2a _c Examples are given to illustrate the use of the tables and formulas in practical cases, and the application of the tables to the calculation of the mutual inductance of coils of rectangular cross-section is treated and illustrated and the necessary formulas developed. The formulas on which the tables are based are collected for reference in an appendix. S P E C T R O P H O T O E L E C T R I C A L S E N S I T I V I T Y OF SOME H A L I D E SALTS O F T H A L L I U M , L E A D , A N D SILVER." By W. W. Coblentz and J. F. Eckford.
[ABSTRACT.] THIS paper, considered in connection with previous publications (Sci. Papers, No. 446 and one, on press), completes a study of the effect of crystal structure, chemical constitution, and atomic weight upon spectrophotoelectrical sensitivity. It is shown that these factors have a definite effect upon the photoelectrical reaction just as previously they were found to have a specific effect upon absorption and reflection spectra. It was found that the spectrophotoelectrical reaction of the halide salts of thallium, lead, and silver is confined to a very narrow region of the violet end of the spectrum, being the narrowest and most sharply defined reaction spectra of all substances yet published, including the photoelectric gas-ionic reaction spectra of the alkali metals. "Scientific Papers, No. 456.
Feb., 1923.1
U.S.
BUREAU OF STANDARDS NOTES.
249
Data are given showing that increasing the atomic weight of the acid element in the salts of thallium shifts the maximum of the spectrophotoelectrical reaction towards the long wave-lengths. The maximum of the spectrophotoelectrical sensitivity of T1 CI is at o.365~; of T1 Br at o.413~ ; and of T1 I, at o-455~. The photoelectrical sensitivity curves of the halide salts of thallium have the outline of what appears to be the typical spectrophotoelectrical reaction curve, vi~., a high photoelectrical reaction on the short wave-length side of the maximum, and a very abrupt termination of the reaction on the long wave-length side of the maximum. Lowering the temperature of T1 I to --60 C. had no appreciable effect upon the position of the maximum of the spectrophotoelectrical reaction. Of the halide salts of lead, Pb C12, Pb Br2, and Pb I2, only the iodide was found to react photoelectrically. The spectrophotoelectrical sensitivity curve of lead iodide appears to be complex with an ill-defined maximum in the region of o.45~, and sharply defined maximum at o.52~. The halide salts of silver appear to be sensitive photoelectrically when melted into a vitreous or semi-vitreous mass. Silver chloride exhibited photoelectrical sensitivity in the region of o.38F, Silver bromide has a maximum at o.46~. The sensitivity curve of silver iodide appears to be wide and complex with maxima at about o.47~ and o.5o~ respectively. In connection with these silver halide salts, an examination of samples of silver nitrate and potassium nitrate showed no photoelectrical sensitivity. G A S E S IN M E T A L S : x. T H E D E T E R M I N A T I O N O F C O M B I N E D N I T R O G E N IN I R O N A N D S T E E L A N D T H E C H A N G E IN F O R M O F N I T R O G E N BY H E A T T R E A T M E N T . 7 By Louis Jordan and F. E. Swindells.
[ABSTRACT.]
THE only form of nitrogen determined in iron or steel by the Allen or acid-solution method is that present as combined nitrogen, probably existing as nitrides of iron, or of such minor constituents as manganese, or aluminum. The solution of the metal sample for nitrogen analysis is made in hydrochloric acid of sp. gr. I.I I. 7Scientific Papers, No. 457. VOL. t95, No. 1166--18