White Precipitate

Addition of barium chloride precipitates white barium sulphite ... 

Two classes of grinding equipment are used to prepare dispersions. The first, the coUoid mill, does not effect a particle size reduction but does break down aggregates of fine particles. CoUoid mills are used for such powders as clays, precipitated whiting, etc. Sometimes these mills are used to process zinc oxide but for dipped mbber products that is not satisfactory. 

After the reaction, 1 ml of water was added to the reaction mixture, and the mixture was adjusted to a pH of 1,0 with concentrated hydrochloric acid while being cooled, and then stirred for 30 minutes. The insoluble matters were filtered off, and the filtrate was adjusted to a pH of 5.5 with triethylamine. This solution was concentrated under reduced pressure, and the residue was diluted with 20 ml of acetone to precipitate white crystals. The crystals were collected by filtration and washed with ethanol to obtain 1.46 g of white crystals of7-[D(-)-0 -emino-(4-hydroxyphenyl)acetamido]-3-methyl-3-cephem-4-carboxylicacid having a decomposition point of 197°C. 

To a solution of 10 g of 2-N-methyl-aminoacetamido-3-o-chlorobenzoyl-5-ethylthiophene in 50 ml of pyridine are added 20 ml of benzene and 1.9 g of acetic acid. The resulting mixture is refluxed with stirring for 10 hours in a flask provided with a water-removing adaptor. The reaction mixture is concentrated, and the residue is extracted with chloroform. The chloroform layer is washed with water and then with a sodium hydrogen carbonate solution, then dried over magnesium sulfate. The chloroform is distilled off under reduced pressure, and toluene is added to the residue. Thus is precipitated white crystalline-5-o-chloropheny -7-ethyl-1 -methyi-1,2-dihydro-3H-thieno-[2,3-e] [ 1,4] diazepin-2-one, MP 105°C to 106°C. 

Applied to certain compounding ingredients (particularly zinc oxide and precipitated whiting) which have been surface-treated to improve their reinforcing power or their ease of incorporating into rubber. Also applied to a lining which has... 

Finely-divided calcium carbonate obtained from natural sources (chalk, limestone or marble) or as a by-product of another chemical process -precipitated whiting. Strictly speaking, the term whiting should be applied only to material prepared by grinding natural chalk . 

Precipitated whiting can be treated with up to 3% of a stearate to coat the particles. When thus treated, dispersion is readily achieved without particle agglomeration. Treated whitings give good product appearance and reasonably high physical properties. 

Thiourea (SC(NH2)2) This solution will slowly precipitate sulphur (seen as a fine white precipitate—white instead of the usual yellow of sulphur possibly due to size quantization of the finely divided precipitate ). However, it can usually be kept over a period of weeks or even months in a stoppered bottle without major adverse effects, although for optimum reproducibility a fresh solution may be preferred. If a prepared stock solution is used, filtration of this solution before use will minimize the presence of sulphur particles in the deposition solution such particles can act as nucleation centers and accelerate precipitation in the solution. 

A flask was charged with hexafluoro-2,2-bis(3-amino-4-hydroxyphenyl)propane (0.8 mol), pyridine (1.6 mol), and /V- m e t h I - 2 - p rro I i d n e (1.2 kg) and then stirred at ambient temperature, cooled to — 25°C with a dry ice/acetone bath and treated with the dropwise addition of a solution consisting of isophthaloyl chloride (0.364 mol), 4,4 -oxy-bisbenzoyl chloride (0.364 mol), and /V- mcth I-2-pv rro I i done (700 g). The mixture was stirred at ambient temperature for 16 hours and then diluted with 2 liters of acetone and poured into 50 liters of deionized water. The precipitated white powder was recovered by filtration and washed with a mixture of deionized water and water/methanol, 1 1. The polymer was dried under vacuum at 40°C for 24 hours to obtain the product in quantitative yield having a Mw of 6400 Da with a poly-dispersity is 2.1. 

Zn2+(aq) White precipitate White precipitate dissolves to give a colourless solution... 

Magnesia mixture or magnesium reagent Cadmium acetate and dilute acetic acid Zinc sulfate White precipitate soluble in excess reagent but reprecipitated on boiling White precipitate White precipitate insoluble in dilute acetic acid soluble in dilute ammonia solution, yielding a white precipitate on boiling... 

A solution of 70% perchloric acid (60 ml) in water (280 ml) was added to a stirred solution of 5a-androst-2-en-17-one (200.0 g) in ether (1.15 I) at 15°C followed by portionwise addition of N-bromacetamide (112.0 g) over 10 min. After stirring for 1 h the precipitated white crystalline solid was filtered off, washed neutral with ether and water and crystallised to give 2p-hydroxy-3a-bromo-5a-androstan-17-one (172.0 g). The ether layer of the filtrate was washed neutral, dried (Na2S04) and concentrated to give a second crop (28.0 g). The two crops (200.0 g) were suspended in methanol (1 L), 10 N aqueous potassium hydroxide solution (100 ml) added and the mixture slowly distilled over 45 min. Addition of water precipitated the product as a white solid which... 

Step 6. Add 30 mL of cold fuming nitric acid and stir. (Cooling the fuming nitric acid reduces the time required for cooling in an ice bath.) Place the centrifuge tube in an ice bath for approximately 10 minutes. Stir to precipitate white Sr(N03)2. Centrifuge and discard the supernate. (Note if excess calcium salts were in the sample, it may be necessary to dissolve the precipitate in 5 mL water and reprecipitate it with 30 mL fuming nitric acid.)... 

Bromophenyl Phenyl Tellurium Dichloride2 An equimolar mixture of 4-bromophenyl tellurium trichloride and chlorotriphenylstannane in toluene is heated under reflux for 2 h. The reaction mixture is then filtered, ligroin is added to the filtrate, and the precipitated white needles are filtered, and rccrystallized from dichloromethane yield 85% m.p. 143°. 

Dinitrophenoxatellurin1 25 ml of nitric acid (d = 1.50) are cooled in anice/salt bath, 4.3 g (14.5 mmol) of powdered phenoxatellurin are added gradually, and the mixture is heated on a water bath for 0.5 h. The solution is then cooled, water is added, the precipitated white solid is collected, and recrystallized twice from boiling nitric acid (d= 1.42). The 2,8-dinitrophenoxatellurin 10,10-dinitrate is reduced by shaking with aqueous potassium disulfite solution and the product is recrystallized from acetone yield 2.9 g (52%) m.p. 228°. 

The reaction mixture is filtered (Note 4) with suction, and the amine salt is washed with about 200 ml. of benzene. The filtrate and washings are combined and transferred to a 1-1. round-bottomed flask, benzene is removed at reduced pressure, and to the residue is added 500 ml. of 2 A aqueous potassium hydroxide. This mixture is heated under reflux for 4 hours, by which time the solution should become completely homogeneous. The cooled solution is extracted with three 100-ml. portions of ether, then acidified to Congo red with concentrated hydrochloric acid (approximately 95 ml.). After the solution has been cooled in ice for at least 1 hour, the precipitated white solid is collected by suction filtration, washed with water, and recrystallized from a minimal amount of hot water (105-125 ml. required at about 90°). The yield of colorless 6-ketohendecanedioic acid, m.p. 108-109° (Note 5) is 35-37 g. (60-64%). 

Barium" chloride, neutral or alkaline. Do. acid. White precipitate. No precipitate. White precipitate. No precipitate. White precipitate. White precipitate. 

Sodium tetraphenylborate (2.50 g, 7.0 mmole) is dissolved in 20 mL of methanol, and this solution is added dropwise to the yellow solution to precipitate white solids. The solids are collected on a medium-porosity frit and dried in vacuo. 

SYNS AMINOMERCURIC CHLORIDE AMMONI-ATED MERCURY MERCURIC AMMONIUM CHLORIDE, solid MERCURIC CHLORIDE, AMMONIATED MERCURY AMINE CHLORIDE MERCURY AMMONIATED D WHITE MERCURY PRECIPITATED WHITE PRECIPITATE... 

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