Sodium hydroxide precipitation

If the amines are required as their hydrochlorides, picrates can often be decomposed by suspending them in acetone and adding two equivalents of ION HCl. The hydrochloride of the base is filtered off, leaving the picric acid in the acetone. Dowex No 1 anion-exchange resin in the chloride form is useful for changing solutions of the more soluble picrates (for example, of adenosine) into solutions of their hydrochlorides, from which sodium hydroxide precipitates the free base. 

Removal of Pollutants by Lime and Sodium Hydroxide Precipitations... 

Copaux A method for extracting beryllium from beryl. The ore is heated with sodium flu-orosilicate at 850°C. Leaching with water dissolves the beryllium fluoride, leaving the silica and most of the aluminum fluoride as an insoluble residue. Addition of sodium hydroxide precipitates beryllium as the hydroxide. The process was invented by H. Copaux and has been in use in France since 1915 and in the United Kingdom since World War II. 

The metals in wash effluents are then extracted by complexation with added resins. A second approach to recovery of metals is to use a flocculant to separate the metals from soil particles following an acid wash. The metals are then concentrated and recovered by sodium hydroxide precipitation. 

Sodium hydroxide has been examined as a substitute for lime (USEPA 1986). Sodium hydroxide precipitation agents have been shown to generate 12% less dry solids than lime precipitation. 

It was noted that sodium hydroxide-precipitated catalysts were quite active in contrast with comparatively inactive ammonia-precipitated catalysts. Investigation of a series of catalysts with varying sodium content proved that the sodium content of a chromium oxide catalyst has a... 

The pure salt is obtained by the following method from pure cis- [diaquabis-(ethylenediamine)chromium(III)] bromide dihydrate. [Diaquabis(ethylenedi-amine)chromium(III)] bromide dihydrate (2.00 g, 0.00413 mole) (see Sec. G) is dissolved at 0° in 5.00 mL of 0.100 jW hydrochloric acid. To this solution is added a solution of 1.10 g (0.00454 mole) of sodium dithionate dihydrate in 10 mL of water at room temperature. To the filtered solution is added, with stirring and cooling in an ice bath, 23.0 mL of 0.200 M sodium hydroxide. Precipitation of red crystals of cis- [aquabis(ethylenediamine)hydroxochromium(III)] dithionate commences almost instantaneously. After a few minutes the sample is filtered and washed thoroughly with water, 96% ethanol, and then diethyl ether. Drying in air yields 0.9 g (59%) of pure ds-[aquabis(ethylenediamine)hydroxochrom-ium(III)] dithionate. Found Cr, 14.04 N, 15.16 C, 13.17 H, 5.23. 

Lead triethyl, EtsPb.-Sixty-five grams of lead triethyl chloride, covered with 100 c.c. of distilled water, are treated with 40 c.c. of 5-Normal sodium hydroxide and the mixture stirred until solution is complete. Addition of 200 c.c. of 5-Normal sodium hydroxide precipitates the lead triethyl hydroxide, which is separated. Sixty grams of the latter in 200 c.c. of 95 per cent, alcohol are electrolysed with lead electrodes, using a current density of 0-01 amperes per sq. cm. Lead triethyl forms as an oil at the cathode. It is pale yellow in colour, density 1 94, and readily oxidised in air, giving a yellowish powder. It may be distilled in steam, and at 2 mm. pressure it boils at 100° C., but it decomposes when distilled at ordinary pressure. It is still liquid at C. In dilute solution it corresponds to the simple formula,... 

Derivation Precipitation from a solution of a magnesium salt by sodium hydroxide, precipitation from seawater with lime. It occurs naturally as brucite. 

The amounts of these radioactive effluents have been estimated [S2] for two model uranium mills, each with a capacity of 2000 short tons of ore containing 0.2 percent U30g/day. One mill uses a carbonate leach, sodium hydroxide precipitation flow sheet such as that described in Sec. 8.4. The other mill uses an acid-leach, amine extraction flow sheet such... 

Chromic oxide gel heated in air shows that the gel remains amorphous up to a temperature of 300°. At 350°, a very faint x-ray pattern is obtained. The gel heated to 400° shows a distinct pattern of crystalline chromic oxide. It has been reported that ammonia-precipitated gel crystallizes at 350° and the sodium hydroxide-precipitated gel crystallizes at 400°C 10). The gel heated in vacuum up to a temperature of 500° fails to show a clear pattern of crystalline Cr203, as may be expected from the results of D.T.A. 

Fig. 3. Differential thermal analysis of ferric oxide gel. (1) Sodium hydroxide precipitation. (2) Ammonium hydroxide precipitation.

Sodium hydroxide precipitates an oil, which is soluble in dilute acids. 

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