Abstract: Contents of elements in metals, e.g. aluminum in steel, which are present as a total quantity in an elemental/dissolved form and in a non-elemental or separated form, are determined by sparking the surface of the metal under an inert atmosphere. The spectral signal is simultaneously measured as a function of time, and a signal is obtained which initially exhibits an intensity peak, from which the non-elemental or separated element content can be concluded, and the signal then stabilizes at a stationary value from which the total content (C.sub.t) of element can be concluded. The elemental/dissolved proportion (C.sub.s) can be concluded from the total area (P.sub.1) below the peak, from the area (P.sub.2) under the stationary intensity measured over a time (t.sub.2 -t.sub.1) and from the total content (C.sub.t).

Abstract: To eliminate astigmatism and coma in a spectrograph the distance between the entrance slot and a first concave mirror, as well as the relative angular positions of the entrance slot, the plane grating, the two concave mirrors and the focal plane are selected so as to satisfy the following conditions.

Abstract: The invention relates to a coil for producing in a cylindrical space a magnetic field being homogeneous in a direction parallel to the axis of said space, which coil comprises a cylindrical winding concentric with the cylindrical space and having at least one pair of mutually identical windings placed symmetrically with respect to the medial plane of the cylindrical winding perpendicular thereto, and extending in planes perpendicular to the longitudinal axis of the cylindrical winding. The pair of mutually identical windings may be situated at the opposite ends of the cylindrical winding and may have a closeness of winding higher than that of the cylindrical winding.