Precipitates drying

A solution of sodium methoxide (25% w, 115 ml, 532 mmol) in methanol (187 ml) was cooled to — 8 "C under nitrogen. A solution of 2,4,5-trimethoxy-benzaldehyde (25 g, 128 mmol) and methyl azidoacetate (59 g, 513 mmol) in a 1 2 mixture of methanol-THF (50 ml 4- 100ml) was added dropwisc to the sodium methoxide solution with stirring at — 8°C over a period of 45 min. The solution was stirred and kept below 5°C for 2 h. The mixture was then poured onto ice (1 kg) and stirred. The precipitate which resulted was collected by filtration, washed with water and dried over CaCl in a vacuum desiccator. The dried precipitate was dissolved in EtOAc (600 ml) and dried over Na2S04. 

A procedure for using a microwave oven to digest samples of Ni ore and to dry precipitates of nickel-dimethylgloxime is described in this experiment. 

This article describes conditions for using a household microwave oven to dry precipitates for the determination of Gh as AgGl, the determination of S04 as BaS04, and the determination of Ga + as GaG204 H2O. 

Extra-Fine Precipitated Hydroxide. Very fine (< 1 /im-diameter) particle size hydroxide is produced by precipitation under carefully controlled conditions using specially prepared hydroxide seed. Precipitation is usually carried out at low (30 —40°C) temperatures causing massive nucleation of fine, uniform hydroxide particles (Fig. 5). Tray or tumiel Ape dry ers are used to dry the thorouglily washed filter cake to a granular product wliich is easily pulverized to obtain the fine hydroxide. Alternatively, the washed product is spray dried. Precipitation from an organic-free aluniinate Hquor, such as that obtained from the soda—sinter process, fields a very wliite product. Tlie fine precipitated hydroxide is used by the paper and plastic industries as fillers. 

Fig. 14-9. Wet/dry precipitation collector and flow chart for analysis of samples. (DI HjO distilled water). Source "NADP Quality Assurance Report," Central Analytical Laboratory, Illinois Institute of Nafural Resources, Champaign, 111., March 1980.

Figure 14-9 also shows a flowchart for analysis of wet and dry precipitation. The process involves weight determinations, followed by pH and conductivity measurements, and finally chemical analysis for anions and cations. The pH measurements are made with a well-calibrated pH meter, with extreme care taken to avoid contaminating the sample. The metal ions Ca, Mg, Na, and are determined by flame photometry, which involves absorption of radiation by metal ions in a hot flame. Ammorda and the anions Cl, S04 , NO3 , and P04 are measured by automated colorimetric techniques. 

Preparation of Alkaloid Mixture 50 ml of the concentrated benzene solution, obtained as described was rapidly stirred, and a saturated solution of hydrogen chloride in ether added to the concentrated benzene solution until no more precipitate was obtained. The resulting precipitate was recovered by filtration and comprised the crude hydrochlorides of the extracted alkaloids and the hydrochloride of any unrecovered triethylamine. This material was dried by heating at a temperature of about 75°C for 6 hours, the crude, dried precipitate ground with 50 ml of isopropanol and to this slurry was added 1,000 ml of water. The resulting mixture was filtered. To the clear filtrate, cooled to 5°C, there was slowly added with rapid stirring, a 10% aqueous solution of ammonium hydroxide, until complete precipitation was accomplished. The precipitate was filtered off, washed with water and dried by heating at about 75°C for 6 hours. 

Electric ovens. The most convenient type is an electrically heated, thermostatically controlled drying oven having a temperature range from room temperature to about 250-300 °C the temperature can be controlled to within 1 -2 °C. They are used principally for drying precipitates or solids at comparatively low controlled temperatures, and have virtually superseded the steam oven. 

Precipitate about 0.1 g potassium (present as potassium chloride in 50 mL water) with 40 mL of the sodium TPB solution added slowly and with constant stirring. Allow to stand for 30 minutes, filter through a sintered-glass filtering crucible, wash with distilled water, and dry for 1 hour at 120 °C. Shake 20-25 mg of the dry precipitate with 200 mL distilled water in a stoppered bottle at 5-minute intervals during 1 hour. Filter through a Whatman No. 40 filter paper, and use the filtrate as the wash liquid. 

Standard solution of silica. Fuse 0.107 g of pure, dry precipitated silica with 1.0 g of anhydrous sodium carbonate in a platinum crucible. Cool the melt, dissolve it in de-ionised water, dilute to 500 mL, and store in a polythene bottle. 1 mL = 0.1 mg Si. Dilute as appropriate, say, to 1 mL = 0.01 mg Si. 

In the polymer industry, post-reaction product treatment processes such as liquid-solid separation, drying, precipitation, particle size control, and polymer purification are very complex and costly. Future polymer plants should be designed such that process equipment can be easily and quickly converted to making new products at minimal cost and with... 

In the OH series, two phases were detectable by XRD in the dried precipitate. One was a phase with the pyroaurite structure, carbonate having presumably arisen from atmospheric CO2, and the other brucite, Mg(OH)2, 0 which pyroaurite is closely related structurally. For both the CCP and IP series, the only structure identifiable in the dried precipitate was that of magnesium hydroxy carbonate. X-ray analysis of the calcined precursors showed MgO together with y-Fe203 in the case of the OH series and HT, but -Fe203 with the CCP and IP series. MgFe204 spinel was also detectable in some cases. 

Successful methods entail precipitation of the amylose from solution as an insoluble complex, which is removed by high-speed centrifuging the amylopectin is isolated from the supernatant liquor by precipitation with alcohol or, more satisfactorily, by freeze-drying. (Precipitation with alcohol does not always appear to be quantitative, and the physical form of the product obtained by freeze-drying is more satisfactory for subsequent dissolution and esterification.) The amylose can then be further purified by reprecipitation with the same or, preferably, a different complexing agent. 

The drying of the precipitates conventionally leads to hard agglomerates, which densify still more during the calcination to oxides. In the freeze dried precipitates only soft agglomerates are formed with fine pores, as shown in Fig. 5.1. During sintering of this product, a high relative density can be achieved at substantially lower temperatures (300-400 °C), as shown in Fig. 5.2. 

Average degrees of polymerization calculated from results of acid hydrolysis of dried precipitated dextrins that remained after removal of fermentable sugars. 

The crucible and cover containing the dried precipitate are weighed. 

The mass of the dried precipitate is converted into moles by using the molar mass. Through use of a stoichiometric ratio, the moles of precipitate are converted to the moles of the substance of interest. The moles of this substance are converted to its mass using the molar mass. 

After bromination of 144 g. (1 mole) of 2-naphthol, the hot solution is poured into water and filtered. The dry precipitate is mixed with a solution of 200 ml. of concentrated sulfuric acid in 500 ml. of technical methanol and heated to vigorous reflux for 4 hours. An oily layer separates during the heating period. The hot mixture is poured into 3 1. of ice and water, and the solids are removed by filtration. The moist solid is triturated with 11. of hot 5% sodium hydroxide. After chilling the mixture to solidify the oil, it is filtered and the product is washed and dried. The 6-methoxy-2-bromonaphthalene is purified by distillation, b.p. 114-118° (0.2 mm.). After distillation the product is most conveniently handled by remelting and pouring it into a mold to solidify. The overall yield is 173-208 g. (73-88%), m.p. 101.5-103°. 

Wet electrostatic precipitators (WESP) are used for removal of liquid contaminants such as sulfuric acid mist, aerosols, and particulate matter. The acid mist and aerosols are typically formed in a WGS by condensation of SO3. Unlike dry precipitators, wet precipitators do not require rapping to remove the dust. The collected mist and particulate matter form a liquid film that runs down a vertical collecting plate. In some cases, a continuous spray of liquid is used to prevent solids deposition on the collecting plates. 

Dust particles, water droplets, and sulfuric acid mist (and if present, ammonium salt aerosols) are electrically charged in the same way as in the dry precipitator. The negatively charged particles are collected on the positive collecting electrodes. 

Elemental composition K 40.26%, Cr 26.78%, O 32.96%. An aqueous solution of the salt is analyzed for potassium and chronium (see Potassium and Chronium). Potassium chromate may be identified by its physical properties and by x-ray methods. Also, an aqueous solution of the salt forms a red precipitate of silver chromate when treated with a solution of silver nitrate. The chromate content may be determined stoichiometrically by weighing the dry precipitate. 

Dissolve the dry precipitate in 3.0 ml of Soln. D and measure the resulting colored solution in a photometer at 625 nm. 

The sample is lyophilized after electroelution. To the dry sample add 500 pi of Soln. A. After vortexing the mixture is incubated in an ice bath at least for 1 h. Then the sample is centrifuged in a refrigerated centrifuge with minimal 3000 x g for 10 min. The supernatant is removed and the remaining pellet (sometimes not visible) is extracted twice with Soln. A as described. The remaining air-dried precipitate is free from SDS. 

The mixture is then filtered by suction, and the precipitate dried in an oven at about 8o° for twelve hours. The dry precipitate is then placed in a i-l. round-bottom flask with reflux condenser, and covered with 800 cc. of xylene. The mixture is agitated by shaking, the xylene heated to boiling for five to ten minutes, and the solution filtered through a hot funnel to remove the calomel which is formed during the reaction. The filtrate is cooled, the />-tolylmercuric chloride filtered off, and the first precipitate extracted again with the filtrate. This is repeated twice. Tn this way 90-100 g. (51-57 per cent of the theoretical amount) of a product which melts at 2330 is obtained. 

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