Water mixtures with strong acids

Place I g. of benzamide and 15 ml. of 10% aqueous sodium hydroxide solution in a 100 ml. conical flask fitted with a reflux water-condenser, and boil the mixture gently for 30 minutes, during which period ammonia is freely evolved. Now cool the solution in ice-water, and add concentrated hydrochloric acid until the mixture is strongly acid. Benzoic acid immediately separates. Allow the mixture to stand in the ice-water for a few minutes, and then filter off the benzoic add at the pump, wash with cold water, and drain. Recrystallise from hot water. The benzoic acid is obtained as colourless crystals, m.p. 121°, almost insoluble in cold water yield, o 8 g. (almost theoretical). Confirm the identity of the benzoic acid by the tests given on p. 347. 

The hydrolysis by alkali is illustrated by the following experimental details for benzamido. Place 3 g. of benzamide and 50 ml. of 10 per cent, sodium hydroxide solution in a 150 ml. conical or round-bottomed flask equipped with a reflux condenser. Boil the mixture gently for 30 minutes ammonia is freely evolved. Detach the condenser and continue the boiling in the open flask for 3-4 minutes to expel the residual ammonia. Cool the solution in ice, and add concentrated hydrochloric acid until the mixture is strongly acidic benzoic acid separates immediately. Leave the mixture in ice until cold, filter at the pump, wash with a little cold water and drain well. RecrystaUise the benzoic acid from hot water. Determine the m.p., and confirm its identity by a mixed m.p. test. 

A stirred mixture of 11 g of 6-chloro-a-methylcarbazole-2-acetic acid ethyl ester, 100 ml ethanol and 100 ml of 3N sodium hydroxide was heated (N2 atmosphere). After 2 hours at reflux, the reaction mixture was concentrated to dryness under reduced pressure. Water (300 ml) and ice (200 g) were added to the residue and concentrated hydrochloric acid was added until the mixture was strongly acid. The acidic mixture was extracted with ether (3 X 200 ml). The ether extracts were combined, washed by extraction with water (3 x 100 ml) and dried over anhydrous magnesium sulfate. Following filtration of the desiccant and evaporation of the solvent, a yield of 9.8 g (98.2%) was obtained. Crystallization from CHCI3 yielded 6.2 g (62.0%) of 6-chloro-0 -methylcarbazole-2-acetic acid, MP 197°-198°C. A second crop of 1.6g,MP 195°-199°C was obtained from the mother liquors. 

C18-0142. The amine group of an amino acid readily accepts a proton, and the protonated form of an amino acid can be viewed as a diprotic acid. The p Zg values for serine (H2 NCHRCO2 H, i = CH2 OH) are p ra(H3 N"") =9.1 and p (002 H) - 2.2. (a) What is the chemical formula of the species that forms when serine dissolves in pure water (b) If this species is titrated with strong acid, what reaction occurs (c) 10.00 mL of 1.00 M HCl is added to 200. mL of 0.0500 M serine solution. This mixture is then titrated with 0.500 M NaOH. Draw the titration curve, indicating the pH at various stages of this titration. 

The REE analysis was carried out in twenty two sand samples by using 0.1 g of dried sample (mesh 200) and digested with strong acid. Digestion was performed in teflon vessels using 4 ml of HCI 04 and 10 ml HF. This mixture was heated and residue dissolved in distilled water. 

Nitro-pentammino-chromic Chloride, [Cr(NH8)5X02]Cl2, is prepared from ehloro-pentammino-chromic chloride by heating it for a short time with water acidified with nitric acid, allowing the mixture to cool slowly, and filtering off the undissolved ehloro-pentammino-salt. The filtrate, which contains aquo-pentammino-ehromic salt, is decomposed with sodium nitrite and a 12 per cent, solution of hydrochloric acid after a few minutes the precipitate formed is collected, washed with water, dissolved in water, and filtered into a strong solution of ammonium chloride. The precipitated crystals are collected, washed with water and alcohol, and obtained as yellow octahedral prisms.-The salt, which is soluble in water, decomposes on heating with hydrochloric acid, giving chloro-pentammino-salt.3... 

Nitric acid is a colourless liquid at room temperature and atmospheric pressure. It is soluble in water in all proportions and there is a release of heat of solution upon dilution. This solubility has tended to shape the process methods for commercial nitric acid manufacture. It is a strong acid that almost completely ionizes when in dilute solution. It is also a powerful oxidizing agent with the ability to passivate some metals such as iron and aluminium. A compilation of many of the physical and chemical properties of nitric acid is presented in Table A.1 of Appendix A. Arguably the most important physical property of nitric acid is its azeotropic point, this influences the techniques associated with strong acid production. The constant-boiling mixture occurs at 121.9°C, for a concentration of 68.4%(wt) acid at atmospheric pressure. 

Slowly add 1000 milliliters of 70% nitric acid to the cooled flask containing the TO mixture (prepared in step 1). After the addition of the 70% nitric acid, heat the resulting mixture with strong stirring to 55 Celsius for 40 minutes. The reaction is exothermic (heat produced) and brown fumes evolve (be careful that the reaction temperature does not go above 55 Celsius. If the temperature begins to climb over 55 Celsius, remove the heat source until the reaction mixtures temperature reduces). After 40 minutes, remove the heat source, and then cool the reaction mixture to 5 Celsius using an ice bath. Then keep at 5 Celsius for 1 hour, and then filter-off the precipitated product. Then wash the precipitated product with 200 milliliters of ice water, and then dry the NTO in an oven at 70 Celsius for approximately 24 hours. 

A mixture of 100 g. (0.75 mole) of o-nitroaniline and 500 ml. of a 1 1 mixture of water and concentrated hydrochloric acid is diazotized by the careful addition of an aqueous solution of 55 g. (0.80 mole) of sodium nitrite at 10°. The mixture is stirred for 15 minutes after the completion of the addition, the solution is filtered, and the filtrate is added slowly with agitation and cooling below 0° to 550 ml. of 25 sodium hydroxide solution. The resulting solution is added to a solution of 135 g. of sodium arsenite in 1250 ml. of water, and the mixture is heated to 60-70° for 2 hours, care being taken not to overheat it. This is followed by acidification with acetic acid, treatment with activated carbon, and the addition of hydrochloric acid until the mixture is strongly acid to Congo red. Cooling the mixture in ice precipitates 110 g. (61 ) of yellow powder, which after one recrystallization from water melts at 235-240° (dec.). 

The treatment of alkaline, crude polyether polyols with strongly acidic cation exchange resins (copolymer of styrene - divinylbenzene with sulfonic acid groups) is a very efficient purification method. The treatment is performed at moderate temperatures (for example 50-70 °C) in the presence of water or, better still, in the presence of a solvent such as methanol or a methanol-water mixture. The treatment may be static (by mixing the crude polyether with cation exchange resin in a reactor, followed by filtration) or, much better, in a dynamic system, in columns with cation exchange resins. The removal of alkaline cations is very efficient, sometimes less than 1 ppm of potassium ions being obtained ... 

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