Product Code Database
This historic book may have numerous typos and missing text
Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1903. Excerpt: ... This action becomes perceptible-when over 80 molecules of acid are present to each molecule of P2Os. The concentration of the acid is also important; the smaller the volume of liquid the less free acid must be present. This solvent action of free acid is prevented by a sufficient excess of molybdic acid solution, which excess must be greater as the amount of free acid is greater. It is also largely overcome by a considerable excess of ammonium nitrate. 5. The yellow precipitate is insoluble in the solution of molybdate of ammonia in nitric acid; also in solutions of ammonium salts, if neutral or only very slightly acid, but if strongly acid they attack the precipitate, which is, however, reprecipitated by the addition of molybdic acid solution to the liquid. It is also practically insoluble in a solution of potassium nitrate when neutral and not too dilute. Solutions of salts of organic acids usually dissolve the precipitate to some extent. From these solutions nitric acid and ammonium nitrate, in some cases, reprecipitate the compound; in others, e. g., with tartaric acid, or oxalic acid, probably not completely. The mineral acids, HCl, HNO3, H2SO4, all have a solvent action on the precipitate even in the presence of ammonium nitrate. HNO3 has the least, HC1 probably the most. Pure water has a tendency to decompose the precipitate to a slight extent and make it run through the filter. 6. Precipitation is much more rapid from hot than from cold solutions, but in time it is probably complete at any temperature The precipitate from hot solutions is denser and more crystalline; from cold, finer and more granular, and harder to filter and wash. 7. Agitation greatly accelerates precipitation in this as well as in other chemical reactions. 8. The precipitate dr...
|
