Abstract: An image is displayed in an electrolytic display by the reversible deposition on electrodes having non-scattering surfaces of a deposit having light scattering properties. The deposit scatters incident light out of the specular direction and the image is formed from one only of the specular and non-specular components of the emergent light.

Abstract: A trivalent chromium electroplating process where the part to be plated is first pretreated with a sulphur compound, in order to accelerate the reduction of chromium ions to chromium metal during a subsequent plating step.

Abstract: A trivalent chromium electroplating solution containing trivalent chromium ions, a complexant, a buffer and an organic compound having a --C.dbd.S group or a --C--S-- group. The complexant is selected to give the chromium complex a stability constant, K.sub.1, in the range 10.sup.8 <K.sub.1 <10.sup.12 M.sup.-1.

Abstract: An electrolytic display device, specifically an electrochromic display based on viologen, employs metal ions in solution to catalyse the reduction of display material at the display electrodes. The metal ions are deposited faster than the display material and subsequently chemically reduce this material. Thallium (I) as the metal catalyst in combination with an oxy-anion of phosphorus accelerates the display reaction without causing undesired precipitation from the solution. Cadmium (II) in combination with sulphate anions is also an effective catalyst. Either a greater amount of display material may be deposited than without the catalyst or the same amount deposited in a shorter time.

Abstract: A trivalent chromium electroplating solution containing trivalent chromium ions, a complexant, a buffer and thiocyanate ions. The thiocyanate is of a molar concentration which is lower than the molar concentration of the chromium ions, and the chromium ion concentration being lower than 0.1 M. The stability constant, K.sub.1, of the solution's chromium complex is in the range 10.sup.8 <K.sub.1 <10.sup.12 M.sup.-1.

Abstract: A trivalent chromium electroplating solution containing trivalent chromium ions, a complexant, a buffer and a sulphur species selected from sulphites and dithionites, the complexant being selected to impart a stability constant, K.sub.1, to the chromium complex which is in the range 10.sup.6 <K.sub.1 <10.sup.12 M.sup.-1. The chromium ion molar concentration is lower than 0.01M. The complexant is selected from aspartic acid, iminodiacetic acid, nitrilotriacetic acid, 5-sulphosalicylic acid or citric acid.

Abstract: A trivalent chromium electroplating solution containing trivalent chromium ions, a complexant, a buffer and a sulphur species having S--O or S--S bonds. The complexant is selected to give the chromium complex a stability constant, K.sub.1, in the range 10.sup.6 <K.sub.1 <10.sup.12 M.sup.-1.

Abstract: A plating solution and method of forming such a solution for plating chromium and its alloys from Cr(III) is disclosed. The solution is an aqueous solution of a chromium(III) thiocyanate complex having at least a ligand other than water or thiocyanate in the inner coordination sphere.

Abstract: A chromium electroplating solution in which the source of chromium comprises an equilibrated aqueous solution of chromium (III) - thiocyanate complexes having supporting electrolyte consisting essentially of potassium sulphate or, preferably, a mixture of potassium and sodium sulphates. The solution is employed as the catholyte in a plating bath in which the catholyte and anolyte are separated by a cation exchange membrane. This all-sulphate bath permits the use of lead anodes, has high efficiency and a good plating range.

Abstract: A very low concentration (below 0.03 M) trivalent chromium plating bath in which the source of chromium is an equilibrated aqueous solution of a chromium (III) - thiocyanate complex gives a deposit of unexpectedly light color. Such a bath is employed to produce thin overcoatings of light colored chromium for decorative applications. The bath and process is also used to plate the initial layer of a thick (greater than 5 micron) deposit for engineering applications, the major part of which is plated from a higher chromium concentration bath. Such thick deposits from a higher concentration bath are more cohesive and smoother when plated over an initial layer from the low concentration bath.

Abstract: A miniature Kerr effect probe is described which may be used to examine surfaces of magnetic material during electroplating or vacuum deposition, without requiring a specially shaped bath or chamber.The probe consists of a U-shaped core with adjacent pole tips of soft magnetic material wound with a coil to provide a magnetic field across the ends of the arms of the core which constitute probe tips. In use, these probe tips are placed adjacent to a surface being examined. Optic fibers are used to direct light to and from the surface.The polarizer and analyzer required for Kerr work may be at the probe tips or remote from the probe tips due to the availability of optic fibers which will transmit polarized light without distortion. The light beam at the probe tips may be collimated or focussed by the optic fiber.

Abstract: An electrochromic display device comprises a single counter electrode and a plurality of display electrodes. The counter electrode is charged and is maintained at a given potential by a donor electrode which transfers charge to the counter electrode in response to the action of a reference electrode. A potentiostat operates to supply current to the donor electrode in accordance with the potential of the counter electrode as sensed by the reference electrode. Both the donor electrode and the counter electrode are preferably of platinum black. The donor electrode is preferably arranged in the manner of a frame about the display area. The counter electrode is preferably grid-shaped.

Abstract: Generation of hydrogen cyanide at the anode in a chromium (III) - thiocyanate plating bath, resulting from oxidation of thiocyanate anions, is prevented by an additive to the electroplating solution which oxidizes at the anode in preference to the thiocyanate, and whose reaction products will not adversely affect the cathode reaction. Such an additive is potassium iodide.

Abstract: An electrochromic display device, preferably employing an organic electrochromic material such as heptyl viologen, has display electrodes with a rough surface in contact with the electrochromic material. The device is operated at a sufficiently high current density so that the diffusion depth of the material conforms to the contours of the electrodes.

Abstract: According to the disclosure, electrochromic display apparatus is provided, comprising, an electrolyte containing an electrochromic material, a plurality of display electrodes in the electrolyte, the display electrodes being connected in at least one group to enable selection of display electrodes, means for selecting at least some display electrodes, means to effect deposition of a visible coating of colored species derived from the electrochromic material onto the selected display electrodes, and means to effect deposition of an invisible coating of the colored species onto all unselected display electrodes, whereby the potentials of selected and unselected display electrodes are equalized.

Abstract: A method for brightening an electroplated chromium deposit wherein the deposited chromium is contacted with a solution having a constituent capable of forming complexes with chromium hydroxide species and of detaching the complexes so formed from the surface of an electroplated deposit. Preferably the solution is an alkaline ferricyanide solution or a solution of sodium dichromate in sulphuric acid.

Abstract: Improved performance is achieved in electrochromic display devices comprising an oxidation-reduction system and an electrolyte wherein the electrolyte comprises hypophosphite anions, phosphite anions, or both.

Abstract: An electrochromic display device has an improved counter electrode arrangement. The device has a plurality of display elctrodes and a counter electrode in contact with a first electrolyte of a primary redox system. The counter electrode is charged to a predetermined potential. A secondary redox system is associated with the primary redox system. A secondary electrode in the secondary redox system is electrically connected to the counter electrode to maintain the charge on the counter electrode at a predetermined potential.

Abstract: An electrochromic display device adapted to be accurately erased has an opaque counter electrode in the shape of a pattern of lines, preferably reticulate, on the underside of the face of the display device through which the display is viewed. The counter electrode is brought to a predetermined potential either by trapping a suitable material capable of a reversible redox reaction at the counter electrode or by initially charging the counter electrode with heptyl vilogen cation radical. This enables voltage erase to be used.

Abstract: Chromium containing deposits free of cracks and having good hardness are plated by the use of a novel aqueous chromium (III) electrolyte. The electrolyte includes an aquo chromium (III)-thiocyanato complex as a source of chromium (III) cations.