Ammonium fluoride salt crystals preparation

Ammonium hydrogen fluoride, NH4F,HF.—Evaporation of a solution of the normal salt at a temperature between 36° and 40° C. expels ammonia, the primary salt crystallizing out. It can also be prepared by the action of ammonia on a solution of hydrogen fluoride, a small proportion of ammonium sulphide or carbonate being added.13 It forms colourless rhombic prisms, readily soluble in water,6 with a density of 1-21114 at 12° C. 

A challenge for industrial syntheses of perfluoroalkanesulfonate tetraalkylammonium salts is the impurities present in technical perfluorooctanesulfonyl fluoride. These impurities cause side reactions that result in tar formation, thus lowering the production yield. One patent claims the preparation of the desired perfluoroalkanesulfonate tetraalkylammonium salts in excellent yields and good purities by reaction of the sulfonyl fluoride with alkoxysilanes (e.g., triethoxymethylsilane) and trial-kylamines (e.g., triethylamine) in a suitable organic solvent (e.g., chlorobenzene, ether, or toluene) as outlined in Scheme 18.1. Under these conditions, the ammonium salts crystallize from the reaction mixture, whereas the fluorosilane by-products remain dissolved in the organic solvent. 

Molybdenum Hexafluoride, MoFg, the only fluoride known vith certainty to exist, is best prepared by the action of fluorine on the finely divided metal at 60° to 70° C., the product being collected in a vessel cooled by a mixture of solid carbon dioxide and alcohol. It forms white crystals which melt at 17° C., the boLling-poiiit of the liquid being 35° C. It is decomposed by water, yielding the blue oxide (see p. 131), but does not react with chlorine, sul2ihur dioxide, or dry air it is absorbed by alkali or ammonium hydroxides, and fomis double salts vith alkali fluorides. It also reacts with ammonia, vith 2>roduction of a brown powder. 

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