Washing predpitates

After cooling to room temperature the mixture is poured onto a mixture of 500 g of crushed ice and 50 ml of concentrated hydrochloric add. The predpitate is filtered with suction, washed with ice-water, pressed and dried in vacuo. Recrystallization from aqueous alcohol affords 98.2 g (91%) of 1-octadecanol, m.p. 58-59°. 

Ethyl bromoacetate (5.54 mL, 50 mmol) in THF (25 mL) was added dropwise to a cooled (ice bath) soln of amine 29 (llOmmol) in THF (25 mL). After stirring for 2.5 h at rt, the mixture was taken to dryness and the residue resuspended in E O. The predpitate was removed by filtration and washed with E O. The combined organic phase was taken to dryness and the residue purified by column chromatography (silica gel, Et20). 4M NaOH (2.5 mL) was added to the soln of /V-alkyl-Gly-OEt (10 mmol) in dioxane (35 mL) and MeOH (12.5 mL). After stirring for 30 min at rt, the mixture was taken to dryness. The residue was dissolved in H20 and the pH adjusted to 9-9.5 with coned HC1. To this mixture a soln of Fmoc-OSu (10 mmol) in MeCN (20 mL) was added in one portion and the pH maintained at 8.5-9.0 with TEA. The MeCN was removed and the residue added to 20% citric acid soln (60 mL). The soln was extracted with EtOAc (3 x 75 mL) and the combined organic layers were washed with H20 and brine, dried (Na2S04), and taken to dryness. The residual oil was recrystallized (EtOAc/hexane). 

Thirty grams of mercuric chloride and 44.5g of potassium thiocyanate are dissolved in 500ml of water and mixed with a solution of 20g of cobalt nitrate 6-hydrate in 50ml of water. A shower of small deep blue crystals of the difficultly soluble complex salt begins to form almost immediately. The mixture is allowed to stand for twelve hours to complete the predpitation and then suction-filtered. The product is washed with three 30ml portions of cold water, drained well, and then rinsed with two 25ml volumes of 95% alcohol to aid in drying. The material is dried in air or in the oven at 100° C. 

Ferric Oxide.—The filtrate from the preceding determination is made up, together with the wash water, to a definite volume (e.g., 250 c.c.) and an aliquot part of it (50 or 100 c.c.) precipitated with ammonia in presence of ammonium chloride the predpitate is collected on a filter and washed. If alumina is present only in negligible quantity, the weight of the caldned predpitate gives the ferric oxide. In the contrary case, the washed and still wet predpitate is dissolved in dilute sulphuric acid and the solution made up to 100 c.c. with water 10 c.c. of this solution are reduced with zinc and the ferrous iron titrated with permanganate (see Vol. I, Limestones and Marls, p. 142). 

Preparation of Allyl Phenyl Ether, f A mixture of 188 g. of phenol, 242 g. of allyl bromide, 280 g. of finely ground calcined potassium carbonate, and 300 g. of acetone is refluxed on the steam bath for eight hours. A heavy predpitate of potassium bromide begins to form soon after the refluxing is started. After cooling, water is added the product is taken up in ether and washed twice with 10% aqueous sodium hydroxide solution. The ether solution is dried over potassium carbonate, and, after removal of the ether, the residue is distilled under diminished pressure. The yield is 230 g. (86%), b.p. 85°/19 mm., dll 0.9845. The residue is so small (6 g.) that the distillation might be omitted unless a very pure product is desired. About 1% of allyl 2-allylphenyl ether (a product of C-alkylation) is formed by this procedure. 

Stirring is continued for one hour after all the diazo solution has been added. The mixture is now filtered and the filtrate concentrated to a volume of approximately 51. this is deep brown in color. Concentrated hydrochloric acid is added in small portions, and the tarry material which separates is filtered off. The add is added until after filtering a clear, pale yellow solution results. The phenylarsonic add is now precipitated by the addition of more hydrochloric acid. An excess must be avoided since it causes a certain amount of the phenylarsonic acid to go into solution. When this neutralized mixture has cooled, the product is filtered off and washed with a little distilled water. Small quantities of phenylarsonic acid remaining in the filtrate may be predpitated as the ferric salt by adding ferric chloride. The yield of white or cream-colored product averages more than 800 g. (50%) and in many cases runs well over 1000 g. (62%). After recrystallization from water the product is practically white and softens at 158°, passing into the infusible anhydride, C6H5ASO2. 

The crude oxide is dissolved in hydrochloric add. To the warm liquor finely divided calcium carbonate is added gradually, with stirring, until no further predpitate is obtained. The precipitate being removed by filtration, the solution is free from iron, arsenic, and silica. The solution is then precipitated with a solution of bleaching powder,2 added slowly with constant stirring until almost the whole of the cobalt is precipitated as black hydrated oxide. By this means practically none of the nickel is thrown down. The precipitate is washed, dried, and calcined to oxide. It is then boiled with sodium carbonate solution to convert any calcium sulphate into carbonate, and after thorough washing, is treated with very dilute hydrochloric acid to remove the calcium carbonate. Finally the oxide is washed, dried, and calcined. 

Chloride in the presence of iodide (bromide being absent) Acidify the solution with dilute nitric add, add excess silver nitrate solution, and filter reject the filtrate. Wash the predpitate with dilute ammonia solution and collect the washings. Add dilute nitric acid to the washings a white precipitate of silver chloride indicates the presence of chloride. 

Summary Acetone-P can be prepared in a rather simple manner by adding concentrated hydrogen peroxide to an acetone solution in the presence of sulfuric add. The product later predpitates, is collected by filtration, washed, and then dried in a desiccator. 

Alcohol is by far the most important predpitation agent used with nucleic acids. Predpitation is usually carried out with 2-3 (v/v) of ethanol or 1 (v/v) of isopropanol in the presence of 0.1-0.5 M Na or K acetate at pH 5.0 and 0 °C salt concentrations higher than 1 M interfere with precipitation. Monovalent cations and ethanol produce a conformational change in the nudeic add which leads to precipitation. For quantitative predpitation, the mixture should be kept for 15 min at -70 °C or 30 min at -20 °C. This is particularly important for dilute solutions (< 10 pg ml-1) more concentrated solutions, above about 0.25 mg ml-1, are predpitated quantitatively even at room temperature. Sodium and potassium acetate salts in the mixture are partially predpitated with the nuddc acid, but they can be removed by washing... 

To a soln of the amino add (20 mmol) in 2 M NaOH (10 mL) and dioxane (20 mL) freshly prepared or recrystallized (from petroleum ether) Nps-Cl (92 22 mmol) was added in 10 equal portions over 15 min, whilst 2 M NaOH (12 mL) was added dropwise with vigorous stirring. The mixture was diluted with HjO (200 mL), filtered from predpitated disulfide, overlayered with EtOAc and acidified with 0.5 M H2SO4 (or aq KHSO4). Upon extraction with EtOAc or EtjO, or with their mixture (1 1), the combined extracts were repeatedly washed with H2O and then dried (Na2S04). The soln was concentrated and upon addition of DCHA (4mL) the crystalline products were collected and washed with Et20/petroleum ether yield 40-90%. 

The viscous solution, while still hot, is dissolved in 4 1. of water, and a solution of 400 g. of sodium hydroxide in 600-800 cc. of water is added. After thorough cooling in an ice bath, the predpitated sodium salt is collected on a large funnel, pressed well, and washed thoroughly with i 1. of half-saturated sodium chloride solution (about 180 g. per liter). The predpitate contains chiefly the sodium 2- and 3-sulfonates. The filtrate contains a mixture of disulfonates and is discarded (Note 3). In order to effect a preliminary concentration of the less soluble... 

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