Zinc salt, additive action

The aspect of the chemistry of the organophosphorodithioate salts most meaningful for their additive action involves their reaction with metals. Luther and Sinha [51] did not find any significant influence of the substrate metals on the thermal decomposition of isomeric zinc dibutyl phosphorodithioates over iron or silver. On the other hand, careful studies by Baumgarten [53] demonstrate the chemisorption of dialkylphosphorodithioate salts on metal, either powder or as evaporated film. Of particular interest are the findings for zinc diisopropyl phos-phorodithioate triply tagged with the radioactive elements Zn, and... 

Copper is positively correlated with zinc in gills of two species of fishes from the Mediterranean Sea. Mixtures of copper and zinc salts in marine or freshwater fishes are more-than-additive in toxicity, producing more deaths in 96h than expected on the basis of individual components. Mixtures of copper and zinc are generally acknowledged to be more-than-additive in toxicity to a wide variety of aquatic organisms. But mixtures of copper (0.0-90.0 p,g/L) and zinc (0.0-1200.0 p,g ) are only additive in action to a marine bacterium (Photobacterium phosphoreum), decreasing its luminescence... 

In addition, many of the organosulfur compounds and organometallic compounds used in rubber compounds as vulcanization accelerators are known to have antioxidant activity. Mercaptobenzimidazole and its zinc salt have been shown to have antioxidant activity. In addition, mercaptobenzimidazole, when combined with other known antioxidants, has been shown to have a synergistic effect in oxidation prevention when metal ion catalyzed oxidation is prevalent. Also, metal and amine salts of dialkyldithio-carbarnates have been shown to have antioxidant action. 

It is useful to mention here more specifically some of the additions that inhibit corrosion. Liddiard et al. (1943) reported that 0.(X)5 mg/L of zinc salts can retard corrosive action of some waters, and this type of self-inhibition may often be important in practice. Sanyal et al. (1959), studying atmospheric attack under laboratory conditions with low SO2, observed that corrosion on steel is reduced in the presence of zinc not in contact with steel. Presumably, that is, zinc ions are transmitted to the steel surface. 

Foam films stabilized by anionic surfactants can be destroyed by the addition of an oppositely charged inorganic species or near-stoichiomeric concentrations of metallic ions to form insoluble salts. For example, fatty acids and their derivatives (tall oil, stearate, etc.) can be precipitated by the addition of calcium, aluminium and zinc salts (forming insoluble salts of the acids). There have been several attempts to relate the defoaming action to the solubility product of the particles. A typical series of results for metal oleates are shown in Figure 8.4. The influence of hydrophobic calcium fatty acid soaps on foaming, and quantification of the data in terms of the solubility product of the calcium and sodium fatty acids have also been reported. Cationic surfactants added to foam stabilized by anionic surfactants could also destroy the foam. Unfortunately, due to the formation of solid contaminants and the adverse consumption of chemicals, precipitation antifoamers are used infrequently in industry. 

Feitknecht has examined the corrosion products of zinc in sodium chloride solutions in detail. The compound on the inactive areas was found to be mainly zinc oxide. When the concentration of sodium chloride was greater than 0-1 M, basic zinc chlorides were found on the corroded parts. At lower concentrations a loose powdery form of a crystalline zinc hydroxide appeared. A close examination of the corroded areas revealed craters which appeared to contain alternate layers and concentric rings of basic chlorides and hydroxides. Two basic zinc chlorides were identified, namely 6Zn(OH)2 -ZnClj and 4Zn(OH)2 ZnCl. These basic salts, and the crystalline zinc hydroxides, were found to have layer structures similar in general to the layer structure attributed to the basic zinc carbonate which forms dense adherent films and appears to play such an important role in the corrosion resistance of zinc against the atmosphere. The presence of different reaction products in the actual corroded areas leads to the view that, in addition to action between the major anodic and cathodic areas as a whole, there is also a local interaction between smaller anodic and cathodic elements. 

Chlorodifluoromethylketones underwent aldol reactions (Eq. 124) via zinc enolates, to afford good yields of a,a-difluoro-/ -hydroxy ketones, in a study by the Kyoto group [327]. Copper(I) or silver salt catalysis was essential and boron-trifluoride additive appeared to exert a key role in the conversion to the enolate. Earlier [328], chlorodifluoromethyl ketones had been converted to the di-fluoroenoxy silanes by the action of zinc in the presence of chlorotrimethyl silane. A difluoroenoxy silane was used by McCarthy and co-workers [329] to synthesise a kynureninase inhibitor (Eq. 125) Lewis acid-mediated reaction with a chloroglycinate installed the key carbon-carbon bond. 

H. Braconnot showed that an alcoholic soln. of nitric acid is often less active than the aq. soln. He said that the alcoholic soln. acts feebly on bismuth, zinc, and copper because of the low solubility of the nitrates of these metals in alcohol and that it does not attack mercury because of the insolubility of the nitrate in alcohol. P. Pascal discussed the action of mixtures of sulphuric and nitric acids on aluminium, steel, and lead. The addition of sulphuric or nitric acid to a manganic salt or manganese dioxide, in the presence of hydrofluoric, phosphoric, or arsenic acid, may convert the whole of the manganese into the corresponding manganic salt. J. Jannek and J. Meyer found that cone, nitric acid distilled with platinum apparatus contains impurities not found when vessels of fused-quartz are employed. G. P. Baxter and F. L. Grover said that if clean, well-seasoned platinum is used, the results are as good as with quartz provided the acid is free from traces of hydrochloric acid. 

---