Nitrous acid stripping

A bacterial phosphatidylinositol specific phospholipase C (PI-PLC) had been available for many years before it was demonstrated to strip a number of membrane-bound proteins from eukaryotic cell surfaces [1], Such proteins are anchored by a PI moiety in which the 6 position of inositol is glycosidically linked to glucosamine, which in turn is bonded to a polymannan backbone (Fig. 3-10). The polysaccharide chain is joined to the carboxyl terminal of the anchored protein via amide linkage to ethanolamine phosphate. The presence of a free NH2 group in the glucosamine residue makes the structure labile to nitrous acid. Bacterial PI-PLC hydrolyzes the bond between DAG and phosphati-dylinositols, releasing the water-soluble protein polysac charide-inositol phosphate moiety. These proteins are tethered by glycosylphosphatidylinositol (GPI) anchors. 

R. H. Robinson found sodium nitrite to be unsuitable as a fertilizer, particularly in acid soils, owing to losses of nitrogen by decomposition. According to C. Marie and R. Marquis, nitrous acid is liberated from aq. soln. of the alkali nitrites by carbon dioxide, so that a strip of potassium iodide-starch paper suspended over the liquid is coloured blue. 0. Baudisch found that the reduction of nitrite by potassium ferrocyanide and oxygen is sensitive to light. M. Oswald found that the presence of sodium sulphate lowers the solubility of sodium nitrite enormously— at 16°, a sat. soln. of the nitrite alone has 81-6 per cent. NaN02, but a sat. soln. of both salts together has 11-8 per cent, sodium sulphate, and 53-9 per cent, of sodium... 

Chemical absorption has also been developed for NOx removal. One such method uses weak acid (25 to 30 wt. %) to remove nitrogen oxides from the tail gas to form nitrous acid (HN02). Steam stripping regenerates the clean acid for recycle. The removed NOx is compressed and fed to the plant s main absorption column104. 

About 3 g. of the substance is placed in a 6-inch test tube having a strip of potassium iodide starch paper suspended on a glass hook which passes through the stopper. The tube Avith contents is placed in a bath and heated to 65° C., for from fifteen to thirty minutes (depending on specification). No blue color showing presence of nitrous acid should develop. 

Indol, like pyrrol, possesses slight basic properties, and also colours a strip of fir, moistened with acid, red. It forms colourless leaflets, M.P. 52°, which have a peculiax , unpleasant smell. It boils at 245° with partial decomposition. With nitrous acid it yields a nitroso-derivative. Of the salts, only the picrate is stable. With acetic anhydride it forms acetylindol. 

As for the Pu purification process, a modified method is proposed for the effective stripping of plutonium from TBP (27). The nitrous acid acts as "redox reagent for Pu (IV) in the stripping and in the extraction feeds. The addition of 0.1 mol/1 of nitrous acid to the extraction feed is sufficient to the effective stripping of plutonium up to 99.9 %. This modified flow-sheet was demonstrated through the process studies with miniature mixer-settlers. ... 

This solution may also be employed in the test for bromine. If iodine has been found, add small amounts of sodium nitrite solution, warm shghtly and shake with fresh 1 ml. portions of carbon tetrachloride until the last extract is colourless boil the acid solution until no more nitrous fumes are evolved and cool. If iodine is absent, use 1 ml. of the fusion solution which has been strongly acidified with glacial acetic acid. Add a small amount of lead dioxide, place a strip of fluorescein paper across the mouth of the tube, and warm the solution. If bromine is present, it will colour the test paper rose-pink (eosin). 

Weak acid from the bottom of the absorber is let down to 330 kPa for bleaching with air from the axial compressor. This air, with nitrogen peroxide stripped from the acid, flows to the suction of the nitrous-gas compressor together with the main nitrous gas stream from the condenser. 

Nitric acid Nitrogen dioxide mixed with nitrogen oxide, oxygen, nitrogen Nitrous oxides Nitric acid, water Nitric acid manufacture Stripping not practiced... 

Many catalysts used in chemical synthesis can be treated in the same way, often the nitrous oxide/acetylene flame is used because of the refractory nature of the elements to be determined. Harrington and Bramstedt [56] have determined rhenium in electro-chemical surface catalysts by stripping the coating with molten potassium hydroxide/ potassium nitrate. This melt was extracted with hydrochloric acid, the residue was fused with sodium peroxide for further rhenium determination. Titanium, being the substrate on which the catalyst was coated, was added to the standards, an air/acetylene flame and 343.3 nm were used for the finish. 

The long established use of chromium salts in the tanning of leather has been reflected in interest in the determination of chromium in leather extracts. Generally the leather is leached with acids or complexing agents such as oxine to remove the metal salts. Della Monica and McDowell [189] recommended leather strips be air dried at 80°C for 24 h and ground to pass a 10 mesh screen. The powder was vacuum dried at 70°C for 16 h and then 100 mg refluxed with 25 ml 2M hydrochloric acid. The filtered acid was aspirated into a flame. For chromium a fuel-rich air/acetylene flame or a nitrous oxide/acetylene flame is to be recommended. 

The nitric acid from the absorption tower carries nitrous gases which color the liquid brown. Therefore, the acid must be stripped of these nitrous gases by air blowing through the liquor. The resultant gases are fed back to the absorber. 

---