Aqueous solutions absolute neutrality

Colorless crystals, soluble in 2.5 parts of cold, and in 1.5 parts of hot, water, and insoluble in absolute alcohol. The aqueous solution is neutral to litmus paper. 

Colorless, cubical crystals, or white, crystalline powder, soluble in 3 parts of cold, but more readily soluble in boiling, water insoluble in absolute alcohol or other. The aqueous solution is neutral. 

In a 2-1. flask fitted with a total-reflux, variable-take-off distillation head is placed a solution of 53 g. (0.472 mole) of dihydroresorcinol (Note 1), 2.3 g. of -toluenesulfonic acid monohydrate and 250 ml. of absolute ethanol in 900 ml. of benzene. The mixture is heated to boiling and the azeotrope composed of benzene, alcohol, and water is removed at the rate of 100 ml. per hour. When the temperature of the distilling vapor reaches 78° (Note 2), the distillation is stopped and the residual solution is washed with four 100-ml. portions of 10% aqueous sodium hydroxide which have been saturated with sodium chloride. The resulting organic solution is washed with successive 50-ml. portions of water until the aqueous washings are neutral and then concentrated under reduced pressure. The residual liquid is distilled under reduced pressure. The yield of 3-ethoxy-2-cyclohexenone (Note 3), b.p. 66-68.5°/0.4 mm. or 115-121°/11 mm., Mq 1.5015, is 46.6-49.9 g. (70-75%). 

To an ethanolic solution of sodium ethoxide prepared by addition of 0.46 g (0.02 mole) of freshly cut sodium metal in 100 mL of absolute ethanol was slowly added 5.10 g (0.02 mole) of ethyl 4-nitrobenzylthioacetate 28 with stirring at 5°C. The mixture was refluxed for about 4 to 6 hours until the reaction was complete (monitored by tic). The resultant mixture was allowed to cool to room temperature and then added into an ice-water mixture. The solution was neutralized with slow addition of dilute aqueous hydrochloric acid (10%). The precipitated solid was removed by filtration, washed with water, and recrystallized from a dimethylformamide-ethanol (T.l) mixture yielding 2.10 g (76 %) of 29 as a light brown crystalline solid, mp 227°C ir (nujol) (neat (1710 cm ms m/z Til (NT). Anal. Calcd. For C13H11NO4S C, 56.31 H, 3.97 N, 5.05 S, 11.55. Found C, 56.36 H, 3.95 N, 5.01 S, 11.49. 

To a solution of 112 (2.0 g, 43.0 mmol) in 50 mL of dry THF at -65°C was added a solution of 111 (4.45 g, 34.0 mmol) in 100 mL of absolute ethanol containing 5 mL of acetic acid cooled to - 65°C in one portion. After stirring for 15 min., dry triethylamine (4.8 g, 510 mmol) was added. The reaction continued for 24 h with slow warming to room temperature before reducing the volume to 10 mL. The crude 113 was brought to pH 10 with potassium carbonate. The aqueous solution was continuously extracted with chloroform, dried (K2CO3), evaporated onto neutral alumina, placed on a column of neutral alumina (50 g) and eluted with chloroform. The solvent was evaporated and the residue crystallized from ethanol to yield 113 (2.86 g 55%). The yellow solid had a mp = 72.5-73.8°C. 

On evaporating the alcoholic solution under reduced pressure from a water bath held at 50-60° (Note 6) the residue weighs about 540 g. A mixture of 600 cc. of absolute alcohol and 10 cc. of concentrated sulfuric acid (Note 7) is then added. The mixture is then heated on the water bath under a reflux condenser for three hours. The excess of alcohol and some of the water formed are removed by distillation under reduced pressure and the residue again heated for two hours with 300 cc. of absolute alcohol and an additional 4 cc. of concentrated sulfuric acid. The alcohol is removed by distillation under reduced pressure, and when the ester has cooled to room temperature, the sulfuric acid is neutralized with a concentrated solution of sodium carbonate the ester (upper layer) is separated, and the aqueous solution extracted with ether, or preferably benzene about one-tenth of the yield is in the extract. The combined products are placed in a i-l. distilling flask and distilled under reduced pressure after the solvent and alcohol and water have been removed. The ester is collected at 94-990, chiefly at 97-98°/x6 mm. (Note 8). The yield of a product analyzing about 97-98 per cent ethyl cyanoacetate amounts to 474-492 g. (77-80 per cent of the theoretical amount) (Note 9). 

We now consider a transfer reaction of charged particles across the interface of electrodes. For a hydrated particle in aqueous solution, the electrochemical potential of the particle is independent of the electrode potential, though it depend on the activity of the partide (the concentration of the partide), regardless of whether the partide is charged (ion) or noncharged (neutral partide). In contrast, for a charged particle (electron or ion) in the electrode, the electrochemical potential of the particle depends on both the electrode potential E and the absolute activity Xk Pk = A7 lnXk-i-zeE. From Eqn. 7-34 we then obtain Eqn. 7-35 for the reaction order, Ck, with respect to a charged particle k in the electrode if the activity of k is constant ... 

Carbon Disulphide.f — Thoroughly mix 50 cc. of benzene with 50 gin. of alcoholic potassium hydroxide solution (11 gm. of potassium hydroxide in 90 gm. of absolute alcohol), and allow the mixture to stand several hours at a temperature of about 20° C. Shake with about 100 cc. of water, remove the aqueous solution from the benzene, neutralize the latter with acetic acid, and add copper-sulphate solution. No precipitate should form. 

Confirmatory tests for phenols. Iron(III) chloride solution. Dissolve about 0.05 g of the compound in 5 ml of water if the compound is sparingly soluble, prepare a hot saturated aqueous solution, filter and use 1 ml of the cold filtrate. Place the solution in a test tube and add 1 drop of neutral 1 per cent iron(m) chloride solution and observe the colour add another drop after 2-3 seconds. If a transient or permanent coloration (usually purple, blue or green) other than yellow or orange is observed, the substance is probably a phenol (or an enol). If no coloration is obtained, repeat the test as above but substitute absolute ethanol or methanol for water as solvent. 

A 3 per cent solution of hydrazoic acid (synthesis 26A) is neutralized with an aqueous solution of pure potassium hydroxide. The resulting solution of potassium azide is concentrated on the steam bath to incipient crystallization. The solution is then made slightly acid with hydrazoic acid to replace the hydrogen azide lost by hydrolysis. A volume of ethyl alcohol twice that of the solution is added, and the solution is cooled in an ice bath. Since the solubility in alcohol of the alkali and alkaline earth azides is very slight (see table below), precipitation in the form of a white microcrystalline salt takes place readily. From 90 to 95 per cent recovery of the theoretical quantity of potassium azide can be effected. The precipitated azide is filtered on a Buchner funnel and washed with cold absolute alcohol and then with ether. Any traces of adhering solvent may be removed in a vacuum desiccator. In a typical run, 300 ml. of a solution of hydrazoic acid containing 8.5 g. of HN3 was neutralized with potassium hydroxide, and the isolation of potassium azide effected as indicated above. Yield 14.7 g. (91.5 per cent) KN3. 

A solution of 12.6 g. of pure a-methyl-D-glucopyranoside (XXVII) in distilled water is added to 260 cc. of 0.54 M aqueous periodic acid solution (2.1 molecular equivalents). The solution, after being diluted with water to 500 cc., is kept at 20-25° for about twenty-four hours. If desired, the excess periodic acid can be determined by the arsenite method. The rotation of the reaction solution should correspond to [a]i> = +121° calculated for the dialdehyde XXVIII. The solution is neutralized to phenolphthalein with hot strontium hydroxide solution with care to avoid any excess. The precipitate of strontium iodate and strontium periodate is filtered and washed with cold water. After the addition of 1 g. <5f strontium carbonate, the solution is concentrated in vacuum with the water bath at 50° to a volume of about 50 cc., filtered to Temove strontium carbonate, and the concentration (bath, 40°) continued to dryness. The residue is extracted six times with 25-cc. portions of cold absolute ethanol, which separates the dialdehyde completely from slightly soluble strontium salts, as shown by the lack of optical activity of an aqueous solution of these salts. The dialdehyde XXVIII is recovered from the ethanol solution as a colorless syrup in quantitative yield by distillation of the solvent in vacuum with the bath at 40-45°. 

The heat of neutralization of ammonia and hydrogen chloride in aqueous solution is given as 12-27 Cal.6 and 12-45 Cal.7 At ordinary temperature this solution is not absolutely stable.8 When heated, it evolves ammonia, and develops an acidic reaction.9... 

Recrystallise the salt from absolute EtOH, filter the crystals, dry them in vacuo and store them in tightly stoppered bottles because it is hygroscopic. It is soluble in H2O but insoluble in C6H6, Et20 and alkaline aqueous solution. It has UV 258 and 307.5nm (log e 4.50 and 3.50) in EtOH (neutral species). [Craig... 

A series of pyridoxal aroylhydrazones 17 has been synthesized and studied by UV, IR, and JH NMR spectroscopy. In absolute methanol, these hydrazones exist in the neutral form 17a, however, gradual addition of water to the methanol solution results in the appearance of new bands in the UV spectra, indicating the formation of zwitterionic tautomer 17b. In aqueous solution, the equilibrium is greatly shifted toward 17b rather than earlier proposed ketoenamine 17c. The dipolar species 17b are stabilized by intermolecular hydrogen bonding with water molecules (92JCS(P2)213). 

The normal neutral oxalate Zr(C204)2 has been prepared 228) by adding stoichiometric quantities of oxalic acid to a solution of zirconium tetrachloride in absolute methanol. Only oxy species were obtained from aqueous solution. 

Nitrilotriacetlc acid was supplied by the Hampshire Chemical Co., Division of W. R. Grace Co., Nashua, New Hampshire. For feeding studies It was neutralized with 1 M sodium hydroxide to provide a 1% NTA solution. Ethyl nltrllotrlacetate was obtained as a clear colorless viscous oil by refluxing 30g of nltrllotrl-acetlc acid In 1 liter of absolute alcohol In the presence of 3g of toluenesulphonlc acid for forty-eight hours. The alcohol was removed by distillation from a water bath in vacuo, the residue mixed with 100 ml of 0.5 percent sodium bicarbonate solution and extracted with one liter of benzene. The benzene solution was extracted twice more with bicarbonate solution, washed with water and concentrated from a water bath In vacuo. The clear colorless residual oil was dissolved by shaking with an aqueous solution of 1.5 M citric acid and the volume adjusted by addition of distilled water to provide a final solution of 1% NTA ethyl ester as citric acid salt. 

Finally, the authors, as chemical professionals, should defend the manufacturers of eosmetics with pH values of 5.5. There is absolutely no evidence that these companies ever made a claim for the neutrahty of their product. The most they do is declare that it is skin neutral. On a few websites, it is even explained that pH 5.5 is actually acidic, and skin neutral refers to a pH that is the same as the pH of the skin surface. Strictly speaking, pH only makes sense in aqueous solutions. Still, the term skin-neutral is not unacceptable. Such cosmetics do not change the acid-base properties of skin, and even though no one has proved that this is benefieial for the skin, it is certainly not harmful, either (Fig. 4.20). 

A series of increasing concentrations of a chemically pure stimulus material in a neutral substrate (water or oil) may be used to determine sensory thresholds to those compounds. The assessors have to indicate the concentration at which stimulus is perceived for two successive concentrations. Increasing concentrations of sucrose, sodium chloride, citric acid, and caffeine are used for the basic tastes sweet, salt, acid, and bitter. Likewise, the olfactory threshold is determined by using some odorants in aqueous or alcoholic solutions (absolute ethanol is often used as a solvent), to measure the ability of the panelists to identify an odor impression and evaluate their odor memory. 

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