Organic precipitants

Potentiometric titrations - continued EDTA titrations, 586 neutralisation reactions, 578, 580 non-aqueous titrations, 589, (T) 590 oxidation-reduction reactions, 579, 581, 584 precipitation reactions, 579, 582 Potentiometry 548 direct, 548, 567 fluoride, D. of, 570 Potentiostats 510, 607 Precipitants organic, 437 Precipitate ageing of, 423 digestion of, 423... 

The most widely studied deformable systems are emulsions. These can come in many forms, with oil in water (O/W) and water in oil (W/O) the most commonly encountered. However, there are multiple emulsions where oil or water droplets become trapped inside another drop such that they are W/O/W or O/W/O. Silicone oils can become incompatible at certain molecular weights and with different chemical substitutions and this can lead to oil in oil emulsions O/O. At high concentrations, typical of some pharmaceutical creams, cosmetics and foodstuffs the droplets are in contact and deform. Volume fractions in excess of 0.90 can be achieved. The drops are separated by thin surfactant films. Selfbodied systems are multicomponent systems in which the dispersion is a mixture of droplets and precipitated organic species such as a long chain alcohol. The solids can form part of the stabilising layer - these are called Pickering emulsions. 

Precipitates, Organic Particle Remains of Inorganic Organisms... 

A mixture of 100 g. of concentrated sulfuric acid and 50 g. of concentrated nitric acid is added dropwise with vigorous stirring to 50 g, (0.47 mole) of o-xylene cooled to —10° to 0°. The reaction mixture is poured into water, and the precipitated organic matter is separated and washed with dilute aqueous sodium hydroxide solution. The product is distilled from a Claisen flask, and the fraction boiling at 115-130°/15 mm. is collected and redistilled through a 100-cm. Fenske column to give 61 g. (86%) of 3-nitro-l,2-dimethylbenzene boiling at 127-130°/18 mm. The residue from either of the above distillations should not be heated more than necessary, since it may decompose explosively. 

Picrate Explosives.—A most important property of the salts of picric acid, especially ammonimn picrate, is their explosive character. They are used in the manufacture of certain smokeless powders, e.g. melinite and liddite. Picric acid itself is not explosive but the salts are exploded either by percussion or ignition. Picric acid is used as an antiseptic and alleviator in the case of burns. It precipitates organic bases and proteins and is used in this way as a test for proteins. 

Precipitation Ultrafiltration Aqueous two-phase separation Salting-out Isoelectric precipitation Organic solvent... 

Metallic oxinates may also be extracted into organic solvents that are immiscible with water. This method involves another use of oxine and also of other precipitating organic reagents. It also permits the identification and even the quantitative determination of metallic ions. 

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