Hydrogen peroxide stabilisation

The iodometric method has the advantage over the permanganate method (Section 10.95) that it is less affected by stabilisers which are sometimes added to commercial hydrogen peroxide solutions. These preservatives are often boric acid, salicylic acid, and glycerol, and render the results obtained by the permanganate procedure less accurate. 

Figure 10.25 Effect of phosphate stabiliser on Fe(m)-catalysed decomposition of hydrogen peroxide in absence of substrate [237]. Initial concentration 2.9 g/l H202, Phosphonate stabiliser 2 g/l, 95 °C, pH 12...

For satisfactory whiteness on wool, it is essential for the fibre to be well scoured and bleached, either oxidatively with hydrogen peroxide or by reduction using stabilised sodium dithionite. Brightener is usually applied together with the dithionite bleach. To achieve the highest possible whiteness, the wool should first be scoured to remove natural waxes and other contaminants, then bleached with peroxide and finally treated with FBA during a second bleach with dithionite. 

The peroxyacids were until relatively recently the most powerful oxidants of all organic peroxides, and it is often unnecessary to isolate them from the mixture of carboxylic acid and hydrogen peroxide used to generate them. The pine lower aliphatic members are explosive (performic, particularly) at high, but not low concentrations, being sensitive to heat but not usually to shock. Dipicolinic acid or phosphates have been used to stabilise these solutions. The detonable limits of peroxyacid solutions can be plotted by extrapolation from known data. Aromatic peroxyacids are generally more stable, particularly if ring substituents are present [1],... 

Schematic representation of the role of waterglass to keep magnesium ions in solution and of the stabilisation of hydrogen peroxide by magnesium ions. 

Solution C (8.8molT1 hydrogen peroxide). Use the hydrogen peroxide as supplied by the manufacturer, i.e. acid-stabilised to pH 2-3. 

Chlorite is also formed when C102 is reacted with hydrogen peroxide (see also ROS discussion below). Chlorite can be stabilised for many hours at high pH values. In the minute-time scale chlorine dioxide reacts with active chlorine depending on the pH value [(7.31)-(7.32)]. 

Blend of stabilisers and sequestrants for use in hydrogen peroxide bleaching. 

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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