Washing salt solution from vessel

Methyl 4,6-0-benzylidene-3-0-methyl-/ -D-mannopyranoside (1.33 g, 0.45 mmol) was dissolved in CH2C12 (5mL) and pyridine (0.11 mL, 1.3 mmol) and the solution was cooled in an ice-salt bath. Tri-fluoromethanesulfonic anhydride (0.20 mL, 1.2 mmol) was added dropwise (the TLC indicated that the reaction was complete in less than 10 min). The mixture was washed sequentially with ice-cold, dil HC1 and H20, dried (MgS04), and evaporated to give the corresponding trifluoromethanesulfonate derivative, which was taken up in CH2CI2 (5 mL). TASF (0.42 g, 1.37 mmol) was added to this CH2C12 solution whilst the vessel was cooled by an ice salt bath. The vessel was removed from the cooling bath and, after... 

Separation of Si with a collector. To the sample solution, containing not more than 25 pg of Si, in a Teflon or platinum vessel, add 2 ml of the niobium solution and 5 ml of cone. HCIO4 and evaporate the solution to fumes, expelling most of the perchloric acid. Dilute the residue with 10-20 ml of HCIO4 (1+50), stir until the salts dissolve, add some macerated filter paper, filter off the precipitate, and wash it with very dilute perchloric acid. Ignite the filter paper and precipitate in a platinum crucible. Add 1 ml of 5% HF to the cooled crucible and heat in a sealed vessel in a water-bath at 70°C for 30 min. Transfer the solution from the crucible to a polyethylene beaker, dilute with water to -10 ml, and add 5 ml of 3% boric acid solution. 

Fluoroboric acid (tetrafluoroboric acid, fluoboric acid) [16872-11-0] M 87.8, b 130°(dec), pK -4.9. Crystallise fluoroboric acid several times from conductivity water. It can be stored in a glass vessel at room temperature. It is available conunercially as 48% aqueous solution. It is most usefiil for preparing tetrafluoroborate salts which are generally insoluble. For example, addition of the acid to aryldiazonium salt solutions precipitates the more stable aryldiazonium tetrafluoroborate salts which can be washed with H2O to remove impirrities, followed by EtOH and Et20, and stored for short periods of time before further use. It is a catalyst for preparing acetals. [Mathers et al. J Am Chem Soc 37 1516 1915, Wamser Christian JAm Chem... 

The conductivity of the water employed should first be determined at 25°. A quantity of finely powdered lead sulphate or silver chloride is then shaken repeatedly with the conductivity water in order to remove any impurities of a comparatively soluble nature. The well-washed salt is then placed along with conductivity water in a hard-glass vessel, which is placed in a thermostat at 25°, and shaken from time to time. After intervals of about quarter of an hour, a quantity of the solution is transferred to a conductivity cell, and the conductivity determined. This is repeated with fresh samples of the solution, until constant values are obtained. 

Carbonates. Basic zirconium carbonate [37356-18-6] is produced in a two-step process in which zirconium is precipitated as a basic sulfate from an oxychloride solution. The carbonate is formed by an exchange reaction between a water slurry of basic zirconium sulfate and sodium carbonate or ammonium carbonate at 80°C (203). The particulate product is easily filtered. Freshly precipitated zirconium hydroxide, dispersed in water under carbon dioxide in a pressure vessel at ca 200—300 kPa (2—3 atm), absorbs carbon dioxide to form the basic zirconium carbonate (204). Washed free of other anions, it can be dissolved in organic acids such as lactic, acetic, citric, oxaUc, and tartaric to form zirconium oxy salts of these acids. 

A setup similar to the preceding one is used in this experiment except that provision should be made for heating the reaction vessel (steam bath, oil bath, or mantle). Lithium aluminum hydride (10 g, 0.26 mole) is dissolved in 200 ml of dry -butyl ether and heated with stirring to 100°. A solution of 9.1 g (0.05 mole) of ra j-9-decalin-carboxylic acid (Chapter 16, Section I) in 100 ml of dry -butyl ether is added dropwise over about 30 minutes. The stirring and heating are continued for 4 days, after which the mixture is cooled and water is slowly added to decompose excess hydride. Dilute hydrochloric acid is added to dissolve the salts, and the ether layer is separated, washed with bicarbonate solution then water, and dried. The solvent is removed by distillation, and the residue is recrystallized from aqueous ethanol, mp 77-78°, yield 80-95 %. 

When well-formed individual crystals have been obtained, filter them on a Witte plate, wash once with dilute nitric acid (1 3), pump as dry as possible, place the moist crystals in a suitable vessel, and put this in a desiccator over sulfuric acid. Watch the crystals carefully, with occasional stirring, and bottle them at once when they are dry. Do not touch them with the fingers, as this will discolor them. If they are allowed to overdry in the desiccator, they lose both crystal water and nitric acid and turn into a sticky mass of brownish-colored basic salt, which will not take up water from the air to reverse the reaction. Consequently, effloresced crystals cannot be used to complete the drying of the moist crystals. If the crystals are exposed to moist air, they deliquesce, undergo hydrolysis in the resulting solution, and form a basic salt. If they are bottled before they are dry, they will in time become discolored. If properly prepared, they will remain perfectly transparent and have a very pretty amethyst color, the intensity of which depends upon the size of the crystals. Crystals of iron alum have the same color. 

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