Ammonium sulfate crystal, role

Reactive crystallization/precipitation plays a role in a number of industrially relevant processes, such as liquid-phase oxidation of para-xylene to produce technical-grade terephthalic acid, the acidic hydrolysis of sodium salicylate to salicylic acid, and the absorption of ammonia in aqueous sulfuric acid to form ammonium sulfate (135). Reactive crystalhzation/precipitation is also widely applied in the pharmaceutical industry, to facilitate the resolution of the enantiomers (diastereomeric crystallization). Here, the racemate is reacted with a specific optically active material (resolving agent) to produce two diastereomeric derivatives (usually salts) that are easily separated by crystallization ... 

These compounds are considered to have a role in the cathodic inhibition properties of lanthanoid salts.They are strong bases and absorb CO from the auto give carbonate species. The solubilities, and basicities of the rare earth hydroxides, as well as the pH values at which they precipitate, decrease with increasing atomic number, with Y(OH)3 being similar to Ho/Er(OH)3 because of similar ionic radii for the Ln ions. Similarly, CeO. xH O is precipitated by addition of base to Ce salts, for example sulfate or nitrate or double salts with ammonium sulfate or nitrate, and by oxidation of Ce(OH)3 precipitates by air (see Section 1.5.1). Single crystals of Ln(OH)3 have been grown by hydrothermal methods. For La(OH)3 to Er(OH)3, the compounds have hexagonal structures with 9-coordination for whereas Lu(OH)3 and Sc(OH)3 have cubic... 

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