Abstract: A mirror is manufactured by plating chromium on one surface of a metal sheet bonded to a composite sheet made up of a synthetic resin sheet and the metal sheet to form a mirror surface. The mirror is worked to have a desired shape. In a modified embodiment, the mirror surface is formed with a decorative pattern.

Abstract: A backelectromotive force of an aluminum electrolysis cell is measured by the steps of: (a) repeatedly measuring voltage V and current I of the cell at a short interval; (b) forming groups of data each including measured values thus obtained within a relative short period; (c) calculating a constant e and its variance Ve with reference to each data group according to a linear regression expressed by an equation:V=r.multidot.I+ewhere r represents an internal resistance of the cell; (d) calculating a backelectromotive force E and its variance V.sub.E at a given time based on the constant e and its variance Ve calculated at the step (c), a backelectromotive force E' and its variance V'.sub.E with reference to a data group preceding the given time and a constant V.sub.T, and according to the following equations:P=(V'.sub.E +V.sub.T)/(Ve+V'.sub.E +V.sub.T)E=P.multidot.e+(1-P).multidot.E'V.sub.E =P.sup.2 .multidot.Ve+(1-P).sup.2 .multidot.(V'.sub.E +V.sub.

Abstract: In an array of rectangular aluminum electrolytic cells, each cell is provided with a plurality of anode electrodes, a plurality of current collecting cathode bars parallel with shorter side walls and located at a bottom of the cell and a plurality of side cathode bus bars extending along longer side walls. The cathode bars are divided into a least two groups. The current flowing through respective groups is collected at their centers on the one side and current flowing through respective groups is collected at both ends thereof on the other side. The collected currents are supplied to the anode electrodes of a next cell.

Abstract: In an aluminum electrolytic cell in which alumina is electrolyzed by electric current flowing between an anode electrode and a cathode electrode, ferromagnetic rods are disposed on the anode electrode in parallel with a shorter end wall of the cell. The ferromagnetic rod is magnetized by a horizontal component of a magnetic field created in the cell by the current to produce a magnetic field containing a vertical component that decreases a gradient of a vertical component of the magnetic field created by the current. The magnetic member may be disposed above or below an aluminum metal layer or above the anode electrode. In the last mentioned case, a ferromagnetic bar may be wound about an anode supporting rod to form a coil having opposite terminals extending in the horizontal direction.

Abstract: In a method of continuously feeding alumina to an aluminum electrolytic cell in which aluminum is prepared by the electrolysis of alumina, the feed of alumina is controlled by starting it when occurrence of an anode effect is detected or anticipated, and the feed is switched between high speed, low speed and interruption during each one of a series of cycles of operation.