Saturation, solutions

Na2S20j. Obtained NaOH solution saturated SO2 at 100 C. Forms 7 and 6 hydrates. Used in photography. 

This type of extraction depends upon the use of a reagent which reacts chemically with the compound to be extracted, and is generally employed either to remove small amounts of impurities in an organic compound or to separate the components of a mixture. Examples of such reagents include dilute (5 per cent.) aqueous sodium or potassium hydroxide solution, 5 or 10 per cent, sodium carbonate solution, saturated sodium bicarbonate solution (ca. 5 per cent.), dilute hydrochloric or sulphuric acid, and concentrated sulphuric acid. 

In a 1500 ml. round-bottomed flask, carrying a reflux condenser, place 100 g. of pure cydohexanol, 250 ml. of concentrated hydrochloric acid and 80 g. of anhydrous calcium chloride heat the mixture on a boiling water bath for 10 hours with occasional shaking (1). Some hydrogen chloride is evolved, consequently the preparation should be conducted in the fume cupboard. Separate the upper layer from the cold reaction product, wash it successively with saturated salt solution, saturated sodium bicarbonate solution, saturated salt solution, and dry the crude cycZohexyl chloride with excess of anhydrous calcium chloride for at least 24 hours. Distil from a 150 ml. Claisen flask with fractionating side arm, and collect the pure product at 141-5-142-5°. The yield is 90 g. 

Nitroso-/S-naphthol, HOCjoHjNO—saturated solution saturate 100 mL of 50% acetic acid with the solid. 

Reference electrode based on the reduction of Hg2Cl2 to Hg in an aqueous solution saturated with KCl that is,... 

The saturated calomel electrode (SCE), which is constructed using an aqueous solution saturated with KCl, has a potential at 25 °C of -hO.2444 V. A typical SCE is shown in Eigure 11.8 and consists of an inner tube, packed with a paste of Hg, HgiCli, and saturated KCl, situated within a second tube filled with a saturated solution of KCl. A small hole connects the two tubes, and an asbestos fiber serves as a salt bridge to the solution in which the SCE is immersed. The stopper in the outer tube may be removed when additional saturated KCl is needed. The shorthand notation for this cell is... 

The solubihty—temperature curves for the Na20—B2O2—H2O system are given in Figure 5 (Table 9). The solubiUty curves of the penta- and decahydrates intersect at 60.6—60.8°C, indicating that the decahydrate, when added to a saturated solution above this temperature, dissolves with crystallisa tion of the pentahydrate and the reverse occurs below this temperature. This transition temperature may be lowered in solutions of inorganic salts, eg, 49.3°C in solutions saturated with sodium sulfate and 39.6°C with sodium chloride. Heats of solution for borax have been determined (67,73) and the manufacturer quotes a value of about 283 kJ/kg (67.6 kcal/mol) (33). 

Potassium Permanganate. Probably the most widely used process for removing traces of hydrogen sulfide from carbon dioxide is to scmb the gas with an aqueous solution saturated with potassium permanganate [7722-64-7]. Sodium carbonate is added to the solution as buffer. The reaction is as foUows ... 

In some instances, ring contraction is accompanied by cyclization to indole derivatives. For example, l-aryl-6-oxo-l,4,5,6-tetrahydropyridazines with a carboxyl or methyl group at position 3 give indoles when treated with an ethanolic solution saturated with hydrogen chloride or in the presence of BF3 etherate. 

Another method of fractional crystallization, in which advantage is taken of different ciystallization rates, is sometimes used. Thus, a solution saturated with borax and potassium chloride will, in the absence of borax seed ciystals, precipitate only potassium chloride on rapid coohng. The borax remains behind as a supersaturated solution, and the potassium chloride crystals can be removed before the slower borax crystalhzation starts. 

Sodium azide [26628-22-8] M 65.0, m 300°(dec, explosive), pK 4.72 (for HN3). Crystd from hot water or from water by the addition of absolute EtOH or acetone. Also purified by repeated crystn from an aqueous solution saturated at 90° by cooling it to 10°, and adding an equal volume of EtOH. The crystals were washed with acetone and the azide dried at room temperature under vacuum for several hours in an... 

Sodium borate (decahydrate, hydrated borax) [1303-96-4] M 381.2, m 75 (loses 5H2O at 60 ), d 1.73. Crystd from water (3.3mL/g) keeping below 55° to avoid formation of the pentahydrate. Filtered at the pump, washed with water and equilibrated for several days in a desiccator containing an aqueous solution saturated with respect to sucrose and NaCl. Borax can be prepared more quickly (but its water content is somewhat variable) by washing the recrystd material at the pump with water, followed by 95% EtOH, then Et20, and air dried at room temperature for 12-18h on a clock glass. 

Isolated tetrasubstituted double bonds do not react under these conditions and the saturation of trisubstituted double bonds is extremely slow, thus limiting the general utility of the method. This difference in reactivity is used to advantage for the selective deuteration of the -double bond in androsta-l,4-diene-3,17-dione (138). In homogeneous solution, saturation usually occurs from the a-side and consequently the deuterium labels are in... 

A solution of crude (53) in 1.5 liters of absolute ethanol is treated with 350 ml of 40% aqueous NaOH solution and refluxed for 7 hr. This solution is then cooled in ice, treated with 650 ml of 12 N HCl and allowed to stand at room temperature overnight. The mixture is stirred and refluxed for 1.5 hr, cooled and filtered. The precipitate is washed well with ethanol and discarded. The filtrate and washings are concentrated under reduced pressure, poured into water and filtered. The filtrate is made alkaline with NaOH solution saturated with K2CO3 and filtered. The precipitate is washed well with water, dried under reduced pressure and sublimed at 165° (0.1 mm) The sublimate is recrystallized from benzene-cyclohexane to yield 7.65g of (54) mp 193-195°. 

The term solubility thus denotes the extent to which different substances, in whatever state of aggregation, are miscible in each other. The constituent of the resulting solution present in large excess is known as the solvent, the other constituent being the solute. The power of a solvent is usually expressed as the mass of solute that can be dissolved in a given mass of pure solvent at one specified temperature. The solution s temperature coefficient of solubility is another important factor and determines the crystal yield if the coefficient is positive then an increase in temperature will increase solute solubility and so solution saturation. An ideal solution is one in which interactions between solute and solvent molecules are identical with that between the solute molecules and the solvent molecules themselves. A truly ideal solution, however, is unlikely to exist so the concept is only used as a reference condition. 

Tile tartaric acid is finely powdered and mi.Ked with half the above quantity (80 c.c.) of absolute alcohol. The mixture is heated on the water-bath with upright condenser until dissolved. The flask is immersed in cold water, and the well-cooled solution saturated with dry hydrochloric acid gas (prepared in the usual way by dropping cone, sulphuric acid into cone, hydiochloric acid, see Fig. 65, p. 93). After standing for an... 

Add and Phenol, if present together, may be separated b) adding sodium bicarbonate in excess and extracting with ether, or by dissolving in caustic soda solution, saturating with caibon dioxide and then extracting with ether. The ether extracts the phenol, n-hicb is insolul le in sodium carbonate, leaving the acid. 

In certain places CO2 can be obtained from natural gas wells. H2S impurity is removed by oxidation using a buffered alkaline solution saturated with KMnOa ... 

After the addition had been completed, the acidic solution containing p-acetylphenyldiazo-nium chloride formed in the above reaction was added dropwise with stirring to a mixture of 530 ml of glacial acetic acid and 530 ml of benzene which had been previously cooled, and the cooled solution saturated with sulfur dioxide and to which had been added 34 g of cupric chloride dihydrate. After the addition had been completed, the reaction mixture was stirred at about 40°C for three hours, and was then poured into 3,000 ml of an ice-water mixture. 

If the compound itself is desired, the salt is dissolved in water and the solution saturated with a mild alkali such as potassium carbonate. The product is then extracted with chloroform, dried, and after removal of the chloroform, distilled. 

A 4 g sample of the crude oil was dissolved in ether and the solution saturated with anhydrous hydrogen chloride. The solid which precipitated was filtered off and recrystal-lized from a mixture of alcohol and ether to yield product weighing3.5 gand melting at 25B°C. It was identified by analysis as 1 -amino-3,5-dimethyladamantane hydrochloride. 

The dl-a-methYl-3,4-dihYdroxYphenylalanine may be made as described in U.S. Patent 2,868,818. Five-tenths of a gram of 3-hYdroxY-4-methoxYphenylalanine was dissolved in 20 ml of concentrated hydrochloric acid, the solution saturated with hydrogen chloride and heated in a sealed tube at 150°C for 2 hours. The dark reaction mixture was concentrated to dryness in vacuo, excess acid removed by flushing several times with ethanol. On dissolving the dark residue in a minimum amount of water and adjusting the clarified solution to pH 6.5 with ammonium hydroxide the compound separated in fine crystals which were filtered, washed with alcohoi and ether. The crystalline product had a MP of 299.5° to 300°C with decomposition. 

A mixture of 4.98 g of acetoacetic acid N-benzyl-N-methylaminoethyl ester, 2.3 g of aminocrotonic acid methyl ester, and 3 g of m-nitrobenzaldehyde was stirred for 6 hours at 100°C in an oil bath. The reaction mixture was subjected to a silica gel column chromatography (diameter 4 cm and height 25 cm) and then eluted with a 20 1 mixture of chloroform and acetone. The effluent containing the subject product was concentrated and checked by thin layer chromatography. The powdery product thus obtained was dissolved in acetone and after adjusting the solution with an ethanol solution saturated with hydrogen chloride to pH 1 -2, the solution was concentrated to provide 2 g of 2,6-dimethyl-4-(3 -nitrophenyl)-1,4-dihydropyridlne-3,5-dicarboxylic acid 3-methylester-5- -(N-benzyl-N-methylamino)ethyl ester hydrochloride. The product thus obtained was then crystallized from an acetone mixture, melting point 136°Cto 140°C (decomposed). 

Table 5.26 The corrosion behaviour of tantalum-molybdenum alloys in concentrated sulphuric and hydrochloric acids at 55°C solutions saturated with oxygen...

The solubility of barium hydroxide in water at 20°C is 1.85 g/100 g water. A solution is made up of256 mg in 35.0 g of water. Is the solution saturated If not, how much more barium hydroxide needs to be added to make a saturated solution ... 

Potassium sulfate has a solubility of 15 g/100 g water at 40°C. A solution is prepared by adding 39.0 g of potassium sulfate to 225 g of water, carefully heating the solution, and cooling it to 40°C. A homogeneous solution is obtained. Is this solution saturated, unsaturated, or supersaturated The beaker is shaken, and precipitation occurs. How many grams of potassium sulfate would you expect to crystallize out ... 

What is the concentration of fluoride ion in a water solution saturated with BaFa JQp = 1.8 X 10-7 ... 

Example 7. Calculate the sulphide ion concentration in a 0.25M hydrochloric acid solution saturated with hydrogen sulphide. 

Polythene wash bottles are sometimes charged with wash liquids other than water. Attention must be drawn to the fact that the components of some wash solutions may pass into the polythene and may be released into the space in the bottle when it is set aside repeated fillings and rinsings may be required to remove the chemicals from the bottle. It is safer to label the wash bottle and to reserve it for the special wash liquid. Such wash solutions include a weakly acid solution saturated with hydrogen sulphide, dilute aqueous ammonia, saturated bromine water, and dilute nitric acid. 

To obtain the most accurate results, a comparison solution, saturated with carbon dioxide and containing the same concentration of sodium chloride (the colour of methyl orange in a saturated aqueous solution of carbon dioxide is sensitive to the concentration of sodium chloride) and indicator as the titrated solution at the end point, should be used. 

This electrode is perhaps next in importance to the calomel electrode as a reference electrode. It consists of a silver wire or a silver-plated platinum wire, coated electrolytically with a thin layer of silver chloride, dipping into a potassium chloride solution of known concentration which is saturated with silver chloride this is achieved by the addition of two or three drops of 0.1M silver nitrate solution. Saturated potassium chloride solution is most commonly employed in the electrode, but 1M or 0.1 M solutions can equally well be used as explained in Section 15.1, the potential of the electrode is governed by the activity of the chloride ions in the potassium chloride solution. 

Attempts to effect ring expansion of methyl 2-azidobenzoate in the presence of other nucleophiles have failed. Thus, photolysis in tetrahydrofuran solution saturated with hydrogen sulfide, or with ammonia, produced methyl 2-aminobenzoate in 54 and 37 % yield, respectively, as the sole identifiable product.197 Photolysis of phenyl azide in ethanolic phenol gave 2-phenoxy-3//-azepine in poor yield (8 %).203,204 2-Mesityl-3//-azepine (10 %) is the surprising, and only tentatively explained, product from the photolysis of phenyl azide in mcsitylene in the presence of trifluoroacetic acid.179... 

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