A Zinc

Zinc(ll) hydroxide is a white gelatinous solid obtained when the stoichiometric quantity of alkali hydroxide is added to a solution of a zinc salt ... 

Addition of sulphide ion to a solution of a zinc salt containing ammonia and ammonium chloride gives a white precipitate of zinc sulphide. 

It was discovered in 1940 that some acetylenic chlorides are converted into allenes by treatment with a zinc-copper couple in ethanol. This method appears to... 

The terminal diyne 320 is prepared by coupling of the zinc acetylide 318 with /rfln.s-l-iodo-2-chloroethylenc (319), followed by elimination of HCI with sodium amide[231]. Similarly, terminal di- and triynes are prepared by using cw-l,2-dichloroethylene[232]. The 1-alkenyl or l-aryl-2-(perefluoroalkyl) acetylene 321 is prepared by the reaction of a zinc acetylide with halides[233]. 

The most commonly used method for reducing an aryl ketone to an alkylbenzene employs a zinc-mercury amalgam m concentrated hydrochloric acid and is called the Clemmensen reduction Zinc is the reducing agent... 

Water Groundwater can be treated in anaerobic bioreactors that encourage the growth of sulfate reducing bacteria, where the metals are reduced to insoluble sulfides, and concentrated in the sludge. For example, such a system is in use to decontaminate a zinc smelter site in the Netherlands (95). 

Acetic anhydride adds to acetaldehyde in the presence of dilute acid to form ethyUdene diacetate [542-10-9], boron fluoride also catalyzes the reaction (78). Ethyfldene diacetate decomposes to the anhydride and aldehyde at temperatures of 220—268°C and initial pressures of 14.6—21.3 kPa (110—160 mm Hg) (79), or upon heating to 150°C in the presence of a zinc chloride catalyst (80). Acetone (qv) [67-64-1] has been prepared in 90% yield by heating an aqueous solution of acetaldehyde to 410°C in the presence of a catalyst (81). Active methylene groups condense acetaldehyde. The reaction of isobutfyene/715-11-7] and aqueous solutions of acetaldehyde in the presence of 1—2% sulfuric acid yields alkyl-y -dioxanes 2,4,4,6-tetramethyl-y -dioxane [5182-37-6] is produced in yields up to 90% (82). 

Electrical Properties. Due to the comparatively low content of polar groups, most commercial ionomers ate very good insulating resins. Typical electrical properties (6) for a zinc ionomer are as foUows ... 

The dehydrogenation of 2-butanol is conducted in a multitube vapor-phase reactor over a zinc oxide (20—23), copper (24—27), or brass (28) catalyst, at temperatures of 250—400°C, and pressures slightly above atmospheric. The reaction is endothermic and heat is suppHed from a heat-transfer fluid on the shell side of the reactor. A typical process flow sheet is shown in Figure 1 (29). Catalyst life is three to five years operating in three to six month cycles between oxidative reactivations (30). Catalyst life is impaired by exposure to water, butene oligomers, and di-j -butyl ether (27). 

In steel-on-steel lubrication with a zinc dialkyl dithiophosphate additive, a complex surface paste appears to form first of zinc particles and iron dithiophosphate. The iron dithiophosphate then thermally degrades to a brown surface film of ZnS, ZnO, FeO, plus some iron and zinc... 

Reforming is completed in a secondary reformer, where air is added both to elevate the temperature by partial combustion of the gas stream and to produce the 3 1 H2 N2 ratio downstream of the shift converter as is required for ammonia synthesis. The water gas shift converter then produces more H2 from carbon monoxide and water. A low temperature shift process using a zinc—chromium—copper oxide catalyst has replaced the earlier iron oxide-catalyzed high temperature system. The majority of the CO2 is then removed. 

Miscellaneous Reactions. Ahyl alcohol can be isomerized to propionaldehyde [123-38-6] in the presence of sohd acid catalyst at 200—300°C. When copper or alumina is used as the catalyst, only propionaldehyde is obtained, because of intramolecular hydrogen transfer. On the other hand, acrolein and hydrogen are produced by a zinc oxide catalyst. In this case, it is considered that propionaldehyde is obtained mainly by intermolecular hydrogen transfer between ahyl alcohol and acrolein (31). 

The order of reactivity with acid is HI > HBi > HCl. Reaction with hydrochloric acid [7647-01-0] to form isopropyl chloride [75-29-6] is faciUtated by a zinc chloride catalyst. 

For increased solubiHty to prevent bloom, shorter-chain carboxyHc acids or zinc carboxylates can be substituted. The use of chain-branched carboxyHc acids reduces the tendency for the formulations to lose sulfur cross-links or revert upon prolonged heating (7). Translucent articles such as crepe soles can use a zinc carboxylate or employ zinc carbonate as a transparent zinc oxide. 

In batteries, a zinc anode undergoes the oxidation reaction,... 

Parameter Garb on—2inc (Zn/Mn O2) Alkalinemanganese dioxide (Zn—Mn02) Mercuricoxide(Z n-HgO) Silveroxide (Zn—A Zinc—air (Zn—02 )... 

Miniature zinc—mercuric oxide batteries have a zinc anode and a cathode containing mercuric oxide... 

Benzal chloride is hydrolyzed to benzaldehyde under both acid and alkaline conditions. Typical conditions include reaction with steam in the presence of ferric chloride or a zinc phosphate catalyst (22) and reaction at 100°C with water containing an organic amine (23). Cinnamic acid in low yield is formed by heating benzal chloride and potassium acetate with an amine as catalyst (24). 

Halobutyl Cures. Halogenated butyls cure faster in sulfur-accelerator systems than butyl bromobutyl is generally faster than chlorobutyl. Zinc oxide-based cure systems result in C—C bonds formed by alkylation through dehydrohalogenation of the halobutyl to form a zinc chloride catalyst (94,95). Cure rate is increased by stearic acid, but there is a competitive reaction of substitution at the halogen site. Because of this, stearic acid can reduce the overall state of cure (number of cross-links). Water is a strong retarder because it forms complexes with the reactive intermediates. Amine cure may be represented as follows ... 

Overflow at the rate of 2700 m (713,000 gal) per day from a zinc-concentrate thickener is treated by ion flotation, precipitate flotation, and untrafine-particle flotation [Nagahama, Can. Min. Metall. Bull., 67, 79 (1974)]. In precipitate flotation only the surface of the particles need be coated with collector. Therefore, in principle less collector is required than for the equivalent removal of ions by foam fractionation or ion flotation. 

Like M( F(7s, S()F(7s can integrate fuel reforming within the fuel cell stack, A prereformer converts a substantial amount of the natural gas using waste heat from the fuel cell, (iornpoiinds containing sulfur (e,g, thiophene, which is cornrnonlv added to natural gas as an odorant) must be removed before the reformer. Typically, a hvdrodesiilfii-rizer combined with a zinc oxide absorber is used. 

REFORMATSKY BLAISE Zincahyiallon Synthesis of -hydrexyesters from cartxinyl derivatives arxl a-haloesters via a zmc reagent (Reformatsky). Synthesis ol eloesleis from nitriles and a-haloesters via a zinc reagent (QIaise). 

The removal of silver from lead is accomplished by die addition of zinc to the molten lead, and slowly cooling to a temperature just above the melting point of lead (600 K). A crust of zinc containing the silver can be separated from the liquid, and the zinc can be removed from tlris product by distillation. The residual zinc in the lead can be removed eitlrer by distillation of the zinc, or by pumping chlorine tluough the metal to form a zinc-lead chloride slag. 

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