Permonosulphuric acid

H0S(0)200S(0)20H. Dibasic acid formed as salts by electrolysis of sulphates at low temperatures and high current density. The acid and persulphates are strong oxidizing agents ( "[S20a] to S04 -t-2 01 volts in acid) but the reactions are often slow. Compare permonosulphuric acid. 

After wetting out, the wool is treated in the same bath with 4-6% of a commercial permonosulphuric acid formulation for 30-60 minutes at 25 °C and pH 4-5... 

Chlorination treatments, of course, are invariably followed by a reductive aftertreatment. In the case of permonosulphuric acid, this is even more important as the sulphite treatment significantly enhances the shrink resistance (Figure 10.46). 

Permonosulphuric acid treatment confers only a modest shrink-resist effect which usually needs to be improved by a subsequent additive treatment. It has been suggested [300] that the most likely mechanism for inhibiting felting by permonosulphuric acid treatment is the removal of degraded protein from below the exocuticle, producing a modified surface with a reduced differential friction. The direct formation from cystine residues of low concentrations of Bunte salts has been confirmed, as indicated in Scheme 10.42. 

Whilst chlorine-based processes are well understood from a mechanistic viewpoint, there are differences between these and the permonosulphuric acid processes. Understanding of the mechanism of permonosulphuric acid treatment has improved in recent years but there are still aspects requiring elucidation [300]. An important difference between these two types of oxidative treatment is that chlorine-based processes lead to scale modification or... 

The sulphite aftertreatment is particularly important with permonosulphuric acid treatment. Evidence for the underlying mechanism is available from analysis of sulphur oxidation products formed in the various processes (Table 10.34). It is evident from these results that the concentration of RSS()5 anionic groups necessary to change the hydration of the fibre surface is achieved by the reaction of bisulphite with cystine monoxide residues to give the required cysteine-S-sulphonate groups [311]. 

When cold aqueous sulphuric acid of suitable concentration is electrolysed in a divided cell, a solution of perdisulphuric acid is obtained at the anode.1 The most favourable concentration of sulphuric acid is 45 to 60 per cent., but even with this the yield is far from quantitative, and, indeed, after a time further electrolysis actually effects a decrease in the quantity of perdisulphuric acid. If the sulphuric acid is too weak the anodic product may be only oxygen, whilst with too concentrated an acid the perdisulphuric acid will undergo conversion into permonosulphuric acid, which decomposes readily. The addition to the electrolyte of a few drops of hydrochloric acid,2 or of a solution of perchloric acid, or of an alkali perchlorate,8 has been found to favour the formation of the perdisulphuric acid it is also advisable that the platinum anode should be smooth or polished and not rough or platinised. 

When dissolved directly in water the reaction is sufficiently vigorous to cause partial conversion into permonosulphuric acid if, however, an ether solution of the acid is placed on cold water, the process of dissolution in the water occurs more gently and an aqueous solution of perdisulphuric acid is obtainable from which the potassium salt can be obtained by careful neutralisation. 

Whether the solution obtained by the electrolysis of sulphuric acid will straightway contain permonosulphuric acid or will only develop it on keeping is dependent on the concentration of the acid present. 

Pure permonosulphuric acid may be obtained by the gradual addition of the theoretical quantity of anhydrous hydrogen peroxide to cold pure chlorosulphonic acid 9... 

Properties.—Pure permonosulphuric acid is an unstable crystalline solid which slowly decomposes even at low temperatures it melts with slight decomposition at 45° C. 

Although permonosulphuric acid is formed from acid-containing solutions of perdisulphuric acid, the latter is the more stable in neutral and alkaline solutions. 

No salt of permonosulphuric acid has been obtained in a pure condition. The acid is monobasic, only one hydrogen atom being dissociable, the ions being H and SOgH. 1... 

In solution, permonosulphuric acid tends to undergo hydrolysis to sulphuric acid and hydrogen peroxide 2... 

Silver nitrate causes vigorous decomposition of a neutralised solution of permonosulphuric acid, ozonised oxygen being rapidly evolved manganese dioxide and lead dioxide produce a similar effect.5... 

For use as an oxidising agent the addition of potassium permanganate to a dilute sulphuric acid solution of permonosulphuric acid has been recommended.2... 

It must be borne in mind that of the hydrogen atoms of permonosulphuric acid, H0.S02.0.0H, only that of the simple hydroxyl group is acidic, the substance being a monobasic acid it is possible that the hydrogen of the — 02H group may become active in the presence of a... 

Detection and Estimation.—Pure solutions of permonosulphuric acid give no yellow coloration with a solution of titanium dioxide in sulphuric acid and so may be distinguished from similar solutions owing their oxidising power to the presence of hydrogen peroxide. 

As will be seen by comparing the formulie of sulphuric acid, S02(OH)2, and sulphamide, S02(NH2)2, hydroxylamineisosulphonic acid is the amide corresponding with permonosulphuric acid, although it has not been directly prepared from this acid. In agreement with this relationship, however, hydroxylamineisosulphonic acid or amidopermonosulphuric acid possesses marked oxidising properties, readily liberating iodine from potassium iodide. 

Further work by E. Muller3 on the production of per-sulphuric acid indicated that permonosulphuric acid or... 

II. From Per-Acids.—Another process smted to the economical preparation of hydrogen peroxide is based on the decomposition of permonosulphuric acid under the influence of water. The acid, prepared by the electrolysis of sulphuric acid or by the interaction of potassium persulphate and sulphuric acid, undergoes gradual hydrolysis according to the equation... 

Nitrosophenylarsinic acid. —10 grams of ato.ryl are added to an ice-cold solution of neutralised permonosulphuric acid (200 c.c. = 1-67 O2), and the whole treated with sodium carbonate until faintly alkaline. After thirty minutes the liquid is filtered and the filtrate acidified, when 8 to 3-5 grams (40 to 50 per cent.) of product separate. It is yellow and readily soluble in hot water, sparingly soluble in cold water, fairly soluble in alkali, alkali carbonates, and acetic acid. In alcohols, ether, chloroform, and pyridine, it is practically insoluble. It gives all the typical nitroso reactions, and when reduced by alkaline hydrosulphite yields 4 4 -diaminoarsenobenzene. 

Wool has been successfully bleached with a stable emulsion of hydrogen peroxide [49] or permonosulphuric acid [50] in perchloroethylene. By this means it appears to be possible to obtain the same degree of whiteness as that attainable in a standard aqueous bleach, but more rapidly and with the use of less peroxide. No stabilising or activating agents are needed, but the bleaching of wool in perchloroethylene seems to be more deleterious to mechanical properties of bleached wool than equivalent aqueous procedure. 

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