Zinc with permanganate

Ferric Oxide.—The filtrate from the preceding determination is made up, together with the wash water, to a definite volume (e.g., 250 c.c.) and an aliquot part of it (50 or 100 c.c.) precipitated with ammonia in presence of ammonium chloride the predpitate is collected on a filter and washed. If alumina is present only in negligible quantity, the weight of the caldned predpitate gives the ferric oxide. In the contrary case, the washed and still wet predpitate is dissolved in dilute sulphuric acid and the solution made up to 100 c.c. with water 10 c.c. of this solution are reduced with zinc and the ferrous iron titrated with permanganate (see Vol. I, Limestones and Marls, p. 142). 

Indirect conversion of 6-methylphenanthridine to phenanthridine-6-carboxylic acid has been achieved by heating with benzaldehyde in the presence of zinc chloride and oxidizing the resulting styryl derivative with permanganate in acetone.245... 

In 1858 Schonbem noticed that when many substances were exposed to atmospheric oxidation, the oxidisable material appeared to combine with half a molecule of oxygen, leaving the other half in the form of hydrogen peroxide or ozone. This is well exemplified by the corrosion of many non-ferrous metals, such as lead and zinc. When lead, mixed with mercury, is shaken with dilute sulphuric acid in the presence of air or oxygen, lead sulphate is formed, together with some hydrogen peroxide. The amount of the latter is readily ascertained by titration of a portion of the liquid with permanganate, and the quantity of sulphuric acid involved is estimated by titration with alkali. It is then found that the amount of peroxide formed is equivalent to that of the lead dissolved. Thus... 

Prepare zinc amalgam for use as follows Add 20- to 30-mesh zinc to a 2% mercuric chloride solution, using about 100 mL of the solution for each 100 g of zinc. After about 10 min, decant the solution from the zinc, then wash the zinc with water by decantation. Transfer the zinc amalgam to the reductor tube, and wash the column with 100-mL portions of 2 N sulfuric acid until 100 mL of the washing does not decolorize 1 drop of 0.1 N potassium permanganate. 

Reduction of Ferric Salts.—The reverse reactions, namely conversion of ferric salts into ferrous, are likewise easily effected by means of the usual reducing agents, such as nascent hydrogen, sulphur dioxide, etc. By the introduction of zinc into an acidified solution of a ferric salt, reduction is rapidly caused. Excess of acid slightly retards the reaction.4 This affords a convenient method of volumetrically determining the presence of ferric iron, the solution after reduction being titrated with permanganate. 

By adding sulphuric acid to a portion of the clear solution and estimating the excess of potassium ferrocyanide by titration with permanganate, the method may be made a convenient one for the estimation of zinc.13... 

The chloride is prepared by the action of dilute hydrochloric acid upon the iiitrate, or by using potassium chloride and carbon dioxide. When treated with moist silver oxide it yields an aqueous solution of the hydi oxide, the latter also being formed when freshly precipitated mercuric oxide, allyl alcohol, and water are shaken together. Reduction of the chloride by zinc and hydrochloric acid gives an odour of allyl alcohol, whilst oxidation with permanganate causes the immediate decomposition of the compound mth the formation of oxalic acid. 

From the pioneering experiments of Spath and Kahovec (128a) which were reviewed in Volume II, the partial formula XXI was proposed for tazettine to accommodate the degradation of the alkaloid to hydrastic acid by permanganate oxidation and to phenanthridine by zinc dust distillation. Tazettine methine, the product of the Hofmann degradation, was formulated as XXII to explain the formation of benzoic acid on oxidation with permanganate. Hofmann degradation of tazettine methine methohydroxide afforded 6-phenylpiperonyl alcohol. 

HAZARD RISK Flammable liquid fire hazard when exposed to heat, flame, sparks, friction or oxidizing materials incompatible with strong oxidziers, active metals such as sodium, potassium and zinc, rust, halogens and amines vapor ignites on contact with fluorine potentially explosive when heated in contact with rust, iron potentially explosive reaction in contact with nitrogen oxide explodes on contact with permanganic acid decomposition emits toxic fumes of SOx NFPA code H 3 F 3 R 0. 

This compound is precipitated when an iron(II) salt solution is mixed with oxalic acid. When dissolved in acid and titrated with permanganate, the latter oxidises both iron(II) and oxalate. If then the titrated solution is reduced by zinc amalgam to regenerate Fe(Il), the latter is then determined by titration with the same permanganate solution. 

Sulphoxides. These are usually solids of low m.p. They may be oxidised in glacial acetic acid solution by potassium permanganate to the corresponding sulphones, and reduced to the sulphides by boiling with tin or zinc and hydro chloric acid. 

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