Alkali damage

Shimizu and Oku (1957) studied the effects of salts on the solubility of wool in 0.1 M KOH. At low salt concentrations the effects of various ions followed the Hofmeister series. Similarly, McPhee (1958b, 1959) has shown that whereas 56 % of wool was dissolved by 1.286 N NaOH at 25°C in 2 hr, only 2 % dissolved when the solution was first saturated with NaCl. There was a corresponding decrease in formation of primary amino groups and in loss of cystine. Not all salts were equally effective in protecting wool against alkali damage. The effectiveness of 2 M solutions of the sodium salts decreased in the order 8203 > SO3 > citrate > COs" > SO 4 > acetate > Cl > Br > NOs" > I > CNS . Cations followed the order Li+, Na+ > K+. Similar rates of alkali uptake were obtained with all salts at a concentration oi 2 M. 

Compared with cathodic blisters, which can be recognized by their alkali content, anodic blisters can be easily overlooked. Intact blisters can be recognized by the slightly lower pH value of the hydrolyzed corrosion product. The pitted surface at a damaged blister cannot be distinguished from that formed at pores. 

The production of OH ions according to Eq. (2-17) or (2-19) in pores or damaged areas is responsible for cathodic disbonding [9,10], where the necessary high concentration of OH ions is only possible if counter-ions are present. These include alkali ions, NH and Disbonding due to the presence of Ca ions is... 

In recent years, a number of protective installations have come into operation, especially where new installations must be maintained, or where older and already damaged installations have to be saved and operating costs have to be lowered. Worldwide, equipment, tanks and evaporators in the aluminum industry and industries using caustic alkalis with a capacity of 60,000 m and a surface area of 47,000 m are being anodically protected. Equipment for electrochemical protection has been installed with a total rating of 125 kW and 12 kA. 

This has a very high resistance to impact damage, even at subzero temperatures. It has good creep strength in dry conditions up to 115°C but degrades by continuous exposures to water hotter than 65°C. It is resistant to aqueous solutions of acids, aliphatic hydrocarbons, paraffins, alcohols (except methanol), animal and vegetable fats and oils, but is attacked by alkalis, ammonia, aromatic and chlorinated hydrocarbons. 

The eye has its own hydraulic system, and disturbances in it may cau.se serious damage to the eye. The normal eye pressure is 22 mm Hg, but when the pressure increases to 28-30 mm Hg, the optic nerve is squeezed and becomes hypoxic. This increase in the eye pressure may be due to acids or alkali causing inflammation in the anterior chamber of the eye, blocking the outflow of aqueous humor back into the systemic circulation. 

Selective removal of the less noble constituent has been demonstrated by chemical analysis in the case of nickel-rich alloys in fused caustic soda or fused fluorides ", and by etching effects and X-ray microanalysis for Fe-18Cr-8Ni steels in fused alkali chlorides. This type of excessive damage can occur with quite small total amounts of corrosion, and in this sense its effect on the mechanical properties of the alloy is comparable with the notorious effect of intercrystalline disintegration in the stainless steels. 

This complex, formerly called pyridine perchromate and now finding application as a powerful and selective oxidant, is violently explosive when dry [1], Use while moist on the day of preparation and destroy any surplus with dilute alkali [2], Preparation and use of the reagent have been detailed further [3], The analogous complexes with aniline, piperidine and quinoline may be similarly hazardous [4], The damage caused by a 1 g sample of the pyridine complex exploding during desiccation on a warm day was extensive. Desiccation of the aniline complex had to be at ice temperature to avoid violent explosion [4]. Pyridinium chlorochromate is commercially available as a safer alternative oxidant of alcohols to aldehydes [5], See Chromium trioxide Pyridine Dipyridinium dichromate See Other AMMINECHROMIUM PEROXOCOMPLEXES... 

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