This investigation was originally conceived as a follow-up on a work by Abt (1965), in which he finds the close binaries, with periods of about 1–100 days, and with spectral types of about A4-F2 (IV-V), to be all Am stars. The stars to be observed were chosen from the ‘Fifth Catalogue of the Orbital Elements of Spectroscopic Binary Stars’ (Moore and Neubauer, 1948). The criteria in making the selection were that the spectral types are A0-A2 and F5-F6 (IV-V) and that the periods are between about 1–100 days.

Spectra of 11 binary systems were obtained at the Coude focus of the 84-inch reflector of the Kitt Peak National Observatory during three nights in May 1967. In addition to the binary stars, 5 standard spectrum stars, i.e. α Lyr (A0V), θ Leo (A2V), σ Boo (F2 V), ι Peg (F5 V) and 110 Her (F6 V), were observed to provide comparisons. The dispersion used was 13·5 Å/mm. Typically 2 or 3 spectra were obtained for each object. A spot densitometer was employed to furnish calibrations for the plates.