Zinc/ions/salts

The role of activators in the mechanism of vulcanization is as follows. The soluble zinc salt forms a complex with the accelerator and sulfur. This complex then reacts with a diene elastomer to form a mbber—sulfur—accelerator cross-link cursor while also Hberating the zinc ion. The final step involves completion of the sulfur cross-link to another mbber diene segment (18). 

Zincon disodium salt (o-[l-(2-bydroxy-5-sulfo)-3-pbenyl-5-formazono]-benzoic acid di-Na salt) [135-52-4, 56484-13-0] M 484.4, m -250-260 (dec). Zincon soln is prepared by dissolving 0.13g of the powder in aqueous N NaOH (2mL diluted to lOOmL with H2O). This gives a deep red colour which is stable for one week. It is a good reagent for zinc ions but also forms stable complexes with transition metal ions. [UV-VIS Bush and Yoe Anal Chem 26 1345 1954 Hunter and Roberts J Chem Soc 820 1941 Platte and Marcy Anal Chem 31 1226 1959] The free acid has been recrystd from dilute H2SO4. [Fichter and Scheiss Chem Ber 33 751 1900.]... 

A salt bridge serves as an ionconducting connection between the two half-cells. When the external circuit is closed, the oxidation reaction starts with the dissolution of the zinc electrode and the formation of zinc ions in half-cell I. In half-cell II copper ions are reduced and metallic copper is deposited. The sulfate ions remain unchanged in the aqueous solution. The overall cell reaction consists of an electron transfer between zinc and copper ions ... 

Cathodic protection is a useful supplement to other forms of water treatment, as a general corrosion inhibiting device in HW boilers, or where specific design configurations can lead to inadequately protected localized metal in steam boilers. Where BW makeup demands are minimal and boiler output is fairly constant, cathodic protection devices can also provide some measure of protection against hardness scales. Calcium carbonate salt is formed as a floc-culant or soft sludge rather than a hard scale, due to the peptizing effects of a zinc hydroxide complex formed from zinc ions in alkaline BW. 

Suppose we have a solution that contains lead(II), mercury(I), silver, copper(II), and zinc ions. The method is outlined in Fig. 11.20, which includes additional cations, and is illustrated in Fig. 11.21. Most chlorides are soluble so, when hydrochloric acid is added to a mixture of salts, only certain chlorides precipitate (see Table 11.4). Silver and mercury(I) chlorides have such small values of Ksp that, even with low concentrations of Cl ions, the chlorides precipitate. Lead(II) chloride, which is slightly soluble, will precipitate if the chloride ion concentration is... 

He compared the infrared spectra of cements with that of zinc polyacrylate salt and found differences. Inspection of his data shows that, unlike the cements, the salt was purely ionic, so that it seems here that cement formation is associated with the formation of coordination complexes. There are no ligand field stabilization effects with the Zn ion because it has a completed d shell (Cotton Wilkinson, 1966). For this reason the... 

In order to outline broadly the mechanism of electrolysis, the behavior of ions of a dissolved salt during electrolysis may be illustrated by the account of the electrolysis of a solution of zinc chloride (Figure 6.16). When zinc chloride is dissolved in water, one zinc ion and two chloride ions are produced from one molecule of salt. The zinc ion will carry two... 

Furylcarbinols with protic acids (fluoroboric acid) may merely give car-benium (furylium) salts.171 Similar cations are accessible via 2-furyldiazo-methane derivatives,172 but in many cases ring opening and prototropic shifts ensue as in Marckwald reactions (Scheme 30).173 A recent development controls solution acidity by using magnesium or zinc ions instead of protons... 

The most important phosphors are sulphides and oxides of transition metals. The sulphides of zinc and of cadmium are the most important materials of the sulphide type. An important condition of achieving a highly efficient phosphor is to prepare a salt of the highest possible chemical purity. The emission of zinc sulphide can be shifted to longer wavelengths by increasingly replacing the zinc ions with cadmium. 

Suppose the salt bridge of a Daniell cell contains ammonium chloride solution, NHiCliaq). As positive zinc ions are produced at the anode, negative chloride ions migrate from the salt bridge into the half-cell that contains the anode. As positive copper(II) ions are removed from solution at the cathode, positive ammonium ions migrate from the salt bridge into the half-cell that contains the cathode. 

This solution is connected by a salt bridge to a second half-cell containing a zinc electrode dipped into a water sample. If the cell potential is read as 0.46 y what will be the zinc ion concentration in this sample of water ... 

N-Acetylpyrazole reacts with zinc ions to form a tris complex, and the salt [ZnL3][BF4]2... 

Acylation. Acylation is the most reliable means of introducing a 3-substituent on the indole ring. Because 3-acyl substituents can be easily reduced to 3-alkyl groups, a two-step acylation—reduction sequence is often an attractive alternative to direct 3-alkylation. Several kinds of conditions have been employed for acylation. Very reactive acyl halides, such as oxalyl chloride, can effect substitution direcdy without any catalyst. Normal acid chlorides are usually allowed to react with the magnesium (15) or zinc (16) salts. The Vilsmeier-Haack conditions involving an amide and phosphorus oxychloride, in which a chloroiminium ion is the active electrophile, frequendy give excellent yields of 3-acylindoles. 

Salt. When compared on a molar basis, the mineral ion salts (ammonium, calcium, rubidium, copper, silver, lead, manganese, cobalt, potassium, and sodium, and cyclohexylamine salt) were as effective as the free gibberellic acid in promoting stem elongation (10,14). As shown in Figure 1, the potassium and zinc salts of A3 were as active as the acid in promoting the growth of d-1 dwarf maize. 

Copper can reduce zinc ions if the resultant copper ions can be kept at a sufficiently low concentration by the formation of an insoluble salt. What is the maximum concentration of Cu2+ in solution if this reaction is to occur (assume 1M Zn2+) ... 

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