Showing papers on "Halide published in 1988"

The silver halide photographic process

Abstract: The light-sensitive elements of conventional photographic materials are crystallites principally of the bromide or chloride salts of silver. Certain chemical modifications employing sulphur and gold compounds are used to maximize the response, and organic dyes are adsorbed to provide sensitivity throughout the visible spectrum. Absorption of a few photons results in the reductive formation of one or more clusters of silver or gold atoms on the surface. These clusters act as catalysts to promote further reduction of the host crystallites during photographic development. The success of the system depends upon the particular physical properties of the silver halides, such as their bonding and electron structure, the dielectric properties, the point defect structure, and the electronic transport characteristics. These are all reviewed, and the ways in which they interact to lead to the favourable photodecomposition are followed in some detail. A nucleation-and-growth mechanism operates to provide sev...

Electronic Ballasts for Metal Halide Lamps

Abstract: (1988). Electronic Ballasts for Metal Halide Lamps. Journal of the Illuminating Engineering Society: Vol. 17, No. 2, pp. 131-140.

Modified collagen compound and method of preparation

Abstract: Chemically-modified collagen is prepared by reacting native collagen with a di or tri-carboxylic acid halide, di or tri-sulfonyl halide, di or tri-anhydride, or di or tri-reactive active ester coupling agent. The reaction is done in a controlled manner so that the degree of cross-linking is limited. Any remaining lysine epsilon amino groups present in the coupled collagen product may be converted to ureido, β-malicamino carboxyamido or sulfonamido groups by isocyanate, epoxy succinic acid, acid halide, anhydride, sulfonyl halide or active ester aminemodifying agents. The resultant soluble product when dissolved in a physiological buffer provides a viscoelastic solution having therapeutic application in a variety of surgical procedures, particularly in ophthalmic surgery. This viscoelastic solution "melts," i.e., exhibits a dramatic loss of viscosity, when subjected to temperatures of between 32° and 48° C. The resultant insoluble product is suspended in physiological buffer and useful in tissue augmentation. The suspension containing the insoluble product exhibits a dramatic loss in viscosity at temperatures between about 40° and 70° C.

Negative‐ion plasma sources

Abstract: Three designs for negative‐ion plasma sources are described. Two sources utilize metal hexafluorides such as SF6 and WF6 to scavenge electrons from electron‐ion plasmas and the third relies upon surface ionization of alkali halide salts on heated alumina and zirconia. SF6 introduced into electron‐ion plasmas yielded negative‐ion plasma densities of 1010 cm−3 with low residual electron densities, (ne/ni∼0.01–0.05). On alumina, plasma densities of 5×109 cm−3 were obtained for CsCl, CsI, and KI and 109 cm−3 for KCl. On zirconia 1010 cm−3 densities were obtained for CsCl. For alkali halide sources, electron densities of ne/ni≲10−4 have been achieved.

Metal halide lamp having vacuum shroud for improved performance

Abstract: A metal halide lamp having a vacuum shroud is disclosed. The vacuum shroud substantially eliminates the detrimental catephoresis effects of operating a metal halide lamp from a low frequency alternating current (A.C.) source or direct current (D.C.) sources, reduces the sodium migration losses typically experienced with a metal halide lamp, reduces the photoelectrons contribution to sodium losses for the metal halide lamp, reduces the detrimental effects of the hydrogen and water that may be within the general confines of such a metal halide lamp, and provides a containment function for an inner envelope that may be operated at a relatively high pressure and possibly experience rupturing to cause the dislodgment of the ruptured material to possibly fracture a glass member confining the metal halide lamp.

Salt mixture for the treatment of psoriasis

Abstract: A composition for the treatment of psoriasis and other skin diseases comprising a salt mixture of defined purity, which is applied to the diseased skin in solution or in gelled form. The composition may be characterized as composed primarily of a mixture of a magnesium halide, such as magnesium chloride, with mixed alkali and alkaline earth metal salts such as sodium and potassium chloride and/or bromide and calcium chloride or bromide. Other cations present in the mixture include strontium, aluminum, iron, lithium and zinc, and the anions include sulphate, hydrogen carbonate, borate, fluoride, silicate, iodide and carbonate.

Process and composition for drying of gaseous hydrogen halides

Abstract: A process for drying a gaseous hydrogen halide of the formula HX, wherein X is bromine, Chlorine, FLuorine, or iodine, to remove water impurity therefrom, in which a scavenger precursor composition is provided, including a support having associated therewith partially or fully alkylated metal alkyl compounds or pendant groups. The precursor composition is reacted with gaseous hydrogen halide to convert the metal alkyl compounds and/or pendant functional groups to the corresponding metal halide compounds and/or pendant functional groups, which in turn react with the water impurity to produce an essentially completely water-free (below 0.1 ppm) gaseous hydrogen halide effluent. The process of the invention has utility for producing high purity, anhydrous gaseous hydrogen halides for semiconductor manufacturing operations.

Modified silica based catalyst

Abstract: The present invention relates to a silica supported magnesium-containing catalytic precursor of reduced SiOH content for reaction with a titanium halide to form a catalyst for the production of a stereospecific alpha olefin polymer characterized in that prior to reacting with titanium halide the magnesium-containing silica is reacted with at least one titanium compound having the formula Ti(OR)nXm or TiRnXm where R is aryl, alkyl or mixtures thereof; X is halogen; n is an integer of 1 to 3; m is 0 or an integer of 1 or 2; and the sum of m and n is 4. It also relates to preparing the catalyst from the precursor.

Process for the production of polyethylene with a broad and/or bimodal molecular weight distribution

Abstract: PROCESS FOR THE PRODUCTION OF POLYETHLENE WITH A BROAD AND/OR BIMODAL MOLECULAR WEIGHT DISTRIBUTION Abstract of the Invention A process for the production of an ethylene homopolymer or copolymer comprising passing ethylene with or without at least one alpha-olefin comonomer having 3 or more carbon atoms into contact with a mixed catalyst system, under polymerization conditions, said mixed catalyst system comprising: (a) the reaction product of (i) a vanadium halide having the formula VX3 wherein X is chlorine, bromine, or iodine and each X is alike or different; (ii) a modifier having the formula BX3or AlR(3-a)Xa wherein X is as defined above; R is an alkyl radical having 1 to 14 carbon atoms; each R is alike or different; and a is 0, 1, or 2 and (iii) an electron donor, which is a liquid Lewis base in which the vanadium halide and modifier are soluble; (b) one of the following: (i) a complex having the formula ZrMgbXc(ED)d wherein X as defined above; ED is an electron donor, which is a liquid Lewis base in which the precursors of the complex are soluble; b is a number from 1 to 3; c is a positive number equal to or less than 4+2b; and d is a number from 4 to 10; or (ii) a vanadium oxy compound having the formula VOX3, VOX2, VOX, or VO2X wherein X is as defined above, or VO(OR)3 wherein R is a monovalent hydrocarbon radical having 2 to 10 carbon atoms and each R can be alike or different, wherein the vanadium halide and the vanadium oxy compound are supported; (c) a hydrocarbyl aluminum cocatalyst; and (d) a halocarbon promoter having the formula ReCX(4-e) wherein R is hydrogen or an unsubstituted or halo substituted alkyl radical having 1 to 6 carbon atoms; each R is alike or different; X is chlorine, bromine, iodine, or fluorine; each X is alike or different; and e is 0, 1, or 2 provided that, if no fluorine is present, e is 2.

Thin Crystal Growth of Alkali Halides from Melt by Using Quartz Cell and Their Optical Properties Due to Excitons

Abstract: A growth method has been developed for preparing thin alkali halide crystals of thicknesses from 0.05 to 50 µm. In this method, the melt is introduced, through capillary action, into a narrow gap between two parallel quartz plates and allowed to solidify. Optical properties of these thin crystal have been measured low temperatures. As an example of this, we examine the case of KI, in which the absorption and emission spectra of excitons are discussed in comparison with those obtained in bulk crystals.

Method for manufacturing a light-sensitive silver halide emulsion

Abstract: A method of producing a silver halide photographic emulsion including the step of: reacting a water-soluble silver salt and at least one water-soluble halide salt containing chloride in aqueous solution in the presence of at least one compound represented by formulae (I) or (II): ##STR1## wherein A1, A2, A3 and A4, which may be the same or different, each represents a nonmetallic atomic group necessary for forming a substituted or unsubstituted heterocyclic ring; B represents a divalent linking group; R1 and R2, which may be the same or different, each represents an alkyl group; X represents an anion necessary for charge balance; m is 0 or 1; and n is 0 or 1; to form light-sensitive silver halide grains having a silver chloride content of at least 50 mol %, selected from octahedral grains, tetradecahedral grains and tablular grains, wherein at least 30% of the surface area of said light-sensitive silver halide grains is composed of (111) planes. The high chloride silver halide emulsions are suitable for rapid development processing with reduced fogging.

Comparative study of E2 and SN2 reactions between ethyl halide and halide ion

Abstract: Trois reactions modeles sont examinees: le fluoroethane avec l'ion fluorure, le chloroethane avec F − et avec l'ion chlorure

Preparation of olefin polymerization catalyst component

Abstract: Solid catalyst components for use in the polymerization of olefins and having improved activity and selectivity are prepared by: (a) halogenating a magnesium compound containing at least one aryloxy, alkyl carbonate or alkyloxy group with a first halide of tetravalent titanium and a first electron donor; (b1) contacting the resulting halogenated product with a second halide of tetravalent titanium; and (c) washing a resulting treated halogenated product with an inert hydrocarbon liquid, wherein a second electron donor is used in step (a) or step (b1) and in that the product of step (b1) is contacted in a step b2 with a third halide of tetravalent titanium at a temperature of 40° to 140° C. and thereafter the treated product is washed in step (c).

Growth of silver halides from the molecule to the crystal. A pulse radiolysis study

Abstract: Halide ions were produced in situ by pulse radiolysis, via electron transfer to dihalomethanes from solvated electrons or hydrogen atoms, and were then used to generate silver halide molecules and larger aggregates. This evolution of silver halide aggregates was studied for the case of silver iodide on the time scale of 10/sup /minus/6/-10/sup 2/ s. Conductivity detection allows determination of the rate of formation of the first AgI molecule. Spectrophotometric detection of the growth of the particles from the stage of the molecular species to colloidal particles of bulk electronic properties is then possible. When the aggregates thus formed approach sizes of ca. 50/degrees/ /angstrom/, their detection by light scattering provides an independent method of size determination. In the region where such measurements are possible, the sizes determined by light scattering agree with sizes calculated assuming confinement excitons in small particles and their electron-hole coulomb screening. A similar approach is suggested for growth studies of other insoluble materials. 13 references, 3 figures.

Method of selectively forming a silicon-containing metal layer

Abstract: A method of selectively forming (growing or depositing) a silicon-containing metal layer on an exposed surface of a semiconductor substrate or a conductor by using a metal halide gas and a silicon hydride gas at a ratio of a flow rate of the latter gas to that of the former gas (e.g., Sin H2n+2 /WF6) of 2 or less, and setting a growth temperature at 200° C. or less. When a Si3 H8 gas and a WF6 gas, in particular, are used at a ratio of the flow rates (Si3 H8 /WF6) of 1.0 or less, and the deposition temperature is set at 100° C. to room temperature, a silicon-containing tungsten layer is selectively deposited (formed).