Zinc amalgamated

Usually prepared by the action of NaCN on benzaldehyde in dilute alcohol. It is oxidized by nitric acid to benzil, and reduced by sodium amalgam to hydrobenzoin PhCHOHCHOHPh by tin amalgam and hydrochloric acid to des-oxybenzoin, PhCH2COPh and by zinc amalgam to stilbene PhCH = CHPh. It gives an oxime, phenylhydrazone and ethanoyl derivative. The a-oxime is used under the name cupron for the estimation of copper and molybdenum. 

Jones reductor A tube containing zinc amalgam. Used for reduction of solutions (e.g. 

Two methods for converting carbonyl groups to methylene units are the Clem mensen reduction (zinc amalgam and con centrated hydrochloric acid) and the Wolff-Kishner reduction (heat with hydra zine and potassium hydroxide in a high boiling alcohol)... 

Reduction ol ketones or aldehydes to hydiocaitxjns by means ol zinc amalgam and acid... 

By application of the Clemmensen reduction,aldehydes and ketones 1 can be converted into the corresponding hydrocarbons 2. As the reducing agent zinc amalgam, together with concentrated hydrochloric acid or gaseous hydrogen chloride, is used. 

In an Evans diagram 89> the mixed potential can easily be found and also be verified by measuring the open circuit potential of a zinc-amalgam electrode in a Cu2+-ion solution. Even the complication by the simultaneous presence of another reducible species, e.g., Pbz+ can be graphically demonstrated for different limiting conditions... 

Fig. 3. Evans-diagram for the cementation of Cu2+ and Pb2 with zinc amalgam of different zinc content. If the zinc concentration in the mercury employed for this special extraction technique is low, the anodic zinc-dissolution current density may be diffusion controlled and below the limiting cathodic current density for the copper reduction. The resulting mixed potential will lie near the halfwave potential for the reaction Cu2+ + 2e j Cu°(Hg) and only Cu2 ions are cemented into the mercury.

If — during this process — the Cu2+-concentration decreases, the mixed potential will shift along the cathodic partial current density curve (like a polarographic curve in this example) toward the equilibrium potential of the zinc amalgam, in case the amalgam reservior is large enough. 

If the zinc amalgam concentration is high, both Cu2 -and Pb2+-ions are simultaneously cemented from the very beginning and the mixed potential lies near the equilibrium potential of the zinc amalgam. 

This figure demonstrates that also under potentiometric conditions (- no external current flow) electrochemical net reactions occur. The EMF of the zinc-amalgam in a given Zn2 -ion solution depends on the current-voltage characteristic of other ions (in this example, Cu2 and Pb2 are interfering ions with respect to the Zn2 equilibrium potential) at the amalgam electrode. EMF drifts are thus explainable. 

The most powerful reductant is therefore zinc amalgam, whilst bismuth amalgam is the least reducing. The final reduction products obtained with these amalgams for a few elements are collected in Table 10.10. 

Light filters for colorimeters, see Filters, optical Limiting cathode potential 509 see also Controlled potential electro-analysis Linear regression 145 Lion intoximeter 747 Liquid amalgams applications of, 412 apparatus for reductions, 413 general discussion, 412 reductions with, (T) 413 zinc amalgam, 413 Liquid ion exchangers structure, 204 uses, 204, 560... 

Reductant equivalent weights of, 847 Reduction 409 by chromium(II) salts, 409 by hydrogen sulphide, 416 by Jones reductor (zinc amalgam), 410 by liquid amalgams, 412 by silver reductor, 414 by sulphurous acid, 416 by tin(II) chloride, 415 by titanium(II[), 410 by vanadium(II), 410 see also Iron(III), reduction of Reduction potentials 66 Reference electrodes potentials, (T) 554 Relative atomic masses (T) 819 Relative error 134 mean deviation, 134... 

The pentammine aqua ion [Ru(NH3)j(H20)]2+, best made by zinc amalgam reduction and aquation of [Ru(NH3)5C1]2+, undergoes extensively studied substitution reactions first order in both the ruthenium complex and the incoming ligand (e.g. NH3, py) and is a convenient source of other... 

Reaction of the osmium(III) pentammines with zinc amalgam gives an osmium species that is stable in solution for some hours (and may be [Oslv(NH3)5(OH)(H)]2+). It is capable of forming Os(NH3)5L2+ adducts with 7r-acids like MeCN [146]. 

The solutions of mer-OsCl3(PR3)3 undergo an interesting reduction with zinc amalgam [155] to form OsCl2(PR3)2L (Figure 1.62), where L is a molecule abstracted from the atmosphere in the reaction flask if a noble gas, incapable of coordination, is employed, coordinative saturation is obtained by dimerization to [(PR3)3OsCl3Os(PR3)3]+. 

B. Amalgamated, Zinc [Mercury alloy (Hg, Zn)]. Zinc powder (206 g., 3.15 moles) is placed in a 1-1. beaker, covered with 250 ml. of aqueous 10% hydrochloric acid, and stirred for 2 minutes. The acid is then decanted and replaced by distilled water, the mixture is stirred, and the supernatant is decanted. Washing is continued in this way until the water is neutral to litmus. A warm solution of 40 g. (0.15 mole) of mercuric chloride [Mercury chloride (HgCl2)] in 250 ml. of distilled water is then poured onto the zinc, and the mixture is stirred gently for 10 minutes. After filtration, the powder is washed with 250 ml. of distilled water, five 250-ml. portions of 95% ethanol, and five 250-ml. portions of anhydrous ether. Drying under vacuum gives 196 g. of zinc amalgam. 

Zinc amalgam, 56, 102 Zinc chloride, 56,11 Zinc fluoride, 58, 77... 

The main system chosen by Wagner and Traud themselves was the corrosion of zinc amalgam in aqueous HCl. They measured the current-potential curves of... 

To describe a specific example of electrode-concentration cells, it is possible to consider two zinc amalgams at different concentrations, dipped into a solution containing zinc ions ... 

Reaction of p-fluorobenzyl chloride with the anion of diethylmethylmalonate ester followed by saponification and decarboxylation leads to acid 9. Polyphosphoric acid cyclization leads to indanone 10. A Reformatsky reaction with zinc amalgam and bromo-acetic ester leads to carbinol 11 which is then... 

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