Solubility impurities and

Purification of anthracene. Dissolve 0-3 g. of crude anthracene (usually yellowish in colour) in 160-200 ml. of hexane, and pass the solution through a column of activated alumina (1 5-2 X 8-10 cm.). Develop the chromatogram with 100 ml. of hexane. Examine the column in the hght of an ultra-violet lamp. A narrow, deep blue fluorescent zone (due to carbazole, m.p. 238°) will be seen near the top of the column. Immediately below this there is a yellow, non-fluorescent zone, due to naphthacene (m.p. 337°). The anthracene forms a broad, blue-violet fluorescent zone in the lower part of the column. Continue the development with hexane until fluorescent material commences to pass into the filtrate. Reject the first runnings which contain soluble impurities and yield a paraffin-hke substance upon evaporation. Now elute the column with hexane-benzene (1 1) until the yellow zone reaches the bottom region of the column. Upon concentration of the filtrate, pure anthracene, m.p. 215-216°, which is fluorescent in dayhght, is obtained. The experiment may be repeated several times in order to obtain a moderate quantity of material. 

Water soluble impurities and their effect can be easily included in equation (1-4), through which they are going to directly affect the particle nucleation rate, f(t). If one assumes a first order reaction of an active radical with a water soluble impurity (WSI) to give a stable non-reactive intermediate, then one simply has to add another term in the denominator of equation (1-4), of the form kwsr[WSI](t)-kv, and to account for the concentration of WSI with a differential equation as follows ... 

The emulsion is separated in the centrifugal contactor (POD), which produces a stream containing water-soluble impurities and a stream of washed solvent. 

There are now two processes in widespread use for making titanium dioxide pigments. In the sulphate process, finely ground ilmenite is digested in sulphuric acid and the iron is reduced and separated as iron(II) sulphate. The titanium(IV) sulphate is hydrolysed by steam to a hydrous oxide, which is thoroughly washed to remove soluble impurities and finally calcined at a temperature of about 1000 °C to give the anatase form of titanium dioxide. 

Prepare a little magnesium oleate by treating a solution of sodium oleate with magnesium sulfate. Carefully wash the precipitate free from soluble impurities and dry at about 110°. Suspend 1 g. of the dry salt in 100 cc. of benzene and provide the flask with a reflux condenser. Boil until solution is obtained. Possibly the product is a colloidal dispersion rather than a very perfect solution. It has been found that a very little sodium oleate mixed with the magnesium oleate rendered the emulsions more permanent. 

Decomposition due to contamination or contact with active surfaces. The rate of decomposition can be increased by the presence of soluble impurities and/or contact with active surfaces. High and low pH will also destabilize hydrogen peroxide. pH affects the activity of the catalytic impurities and the stabilizers which are present.47 Self-heating can rapidly accelerate the decomposition rate of destabilized hydrogen peroxide. Large amounts of oxygen and steam can be formed quickly (Table 1.4). 

In all cases, the latexes were dialyzed to remove water-soluble impurities and salts. This process also removed part of the soap. The dialyzed latexes were then analyzed and reformulated to the desired level of charge with the appropriate emulsifier. 

The most common approach for isolating the element is by precipitation from a solution where it is present in ionic form (see p. 50). Ideally, the constituent under investigation is precipitated out of solution as a water-insoluble compound, so that no losses occur when the precipitate is separated by filtration, washed free of soluble impurities and then weighed. 

Further improvement of throughput in LC-MS analysis may be achieved by step-gradient elution. This elution format is essentially an on-line solid-phase extraction (SPE) process, where the samples are loaded onto the column, washed with aqueous mobile phase to remove water soluble impurities, and compounds are eluted with a mobile phase of high organic content. The technique combines the simplicity of FIA with the benefit of the removal of impurities and buffer components before mass spectrometry detection. In this case, selectivity is achieved by mass spectrometry alone without chromatographic separation. The technique has been used for compound purity assessment and quantitation. An on-line back-flush SPE-MS technique has been used by Marshall for quality assessment of the combinatorial libraries [112]. This back-flush elution procedure provides a very effective in-line removal method... 

When adsorption is finished, one washes carbon with 15 liters of distilled water until one cannot detect any more, in the filtrate, of water soluble impurities, and then one subjects this coal to an elution with 50 liters of methanol added with 10% of concentrated ammonia. The eluate is concentrated to 1 liter under 20 torr at 30° and the acid carboxylic, which crystallized at the end of twenty-four hours, is dried under 1 torr at 80°. The recovery is 45.3 grams is 91% of the theoretical quantity. 

A mixture of 8.0 g diethyl malonate and 9.8 g deoxybenzoin in the presence of 500 mg anhydrous aluminum chloride was heated at 250°C for 1 h. The cold reaction mixture was poured onto water, and NaOH was added. The aqueous solution was washed with ether, and the aqueous layer was acidified with HCl. The aqueous acid solution was extracted with ether, and the organic layers were combined, dried over Na2S04, and concentrated to afford 2.4 g 4-hydroxy-5,6-diphenyl-2-pyrone as an oil that solidified upon standing, in a yield of 18.1%. The solid was triturated with ether to remove soluble impurities and recrystallized from methanol to give a white solid, m.p. 187-188°C. 

El-Sayed and Bandosz used three activated carbon samples of different origin, namely BPL from Calgon and MVP from Norit, both prepared from bituminous coal, and BAX from Westvaco, made from wood, using chemical activation with phosphoric acid for the adsorption of acetaldelyde. These carbons were washed in a soxhlet apparatus to remove water-soluble impurities and then oxidized with nitric acid. The adsorption of acetaldehyde was determined by inverse gas chromatography at infinite dilution and finite concentration. The heats of acetaldehyde adsorption at... 

Water-washed day - Water-washed kaolin has been slurried in water and centrifuged or hydrocycloned to remove impmities and produce specific particle size fractions. The refined slurry is either dewatered (to reduce soluble impurities) and dried, or concentrated to 70% solids and sold in slurry form. Water-washed clays are often treated to improve brightness. This includes chemical bleaching and/or high-intensity magnetic separation to remove iron and titanium impurities. 

---