Diethanolamine is primarily used as an absorbent for acidic gases such as CO?, H?S, and SO?, as a nonionic surfactant, emulsifier, polishing agent, industrial gas purifier, and lubricant. It is employed as a thickener and foam modifier in shampoos and light-duty detergents, and as a softening agent in the production of synthetic fibers and leather. Diethanolamine reacts with 70% sulfuric acid to undergo dehydration and cyclization, forming morpholine (i.e., 1,4-oxazinane). Both morpholine and diethanolamine serve as intermediates in organic synthesis, for example, in the production of certain optical brighteners in the textile industry. Fatty acid salts of morpholine are used as preservatives, and morpholine can also be employed in the synthesis of the central nervous system depressant pholcodine or as a solvent. In analytical chemistry, diethanolamine is used as a reagent and a gas chromatography stationary phase, selectively retaining and separating alcohols, diols, amines, pyridine, quinoline, piperazine, thiols, thioethers, and water. It is utilized as an analytical reagent, gas chromatography stationary phase, softening agent, and lubricant, and is also applied in organic synthesis. It functions as an acidic gas absorbent, oxidant, organic synthesis intermediate, softening agent, and lubricant. As a gas chromatography stationary phase (maximum operating temperature 60°C, solvent methanol), it selectively retains and separates alcohols, diols, amines, pyridine, quinoline, piperazine, thiols, thioethers, and water.