Neutralisation potassium hydroxide

Since the silver salts of the carboxylic acids are usually soluble in dilute nitric acid, they must be prepared by treating an aqueous solution of a neutral salt of the acid (and not the free acid itself) with silver nitrate solution. It is not practicable to attempt to neutralise the acid with sodium or potassium hydroxide solution, because the least excess of alkali would subsequently cause the white silver salt to be contaminated with brown silver oxide. The general method used therefore to obtain a neutral solution j to dissolve the acid in a small excess of ammonia solution, and then to boil the solution until all free... 

For the primary stage (phosphoric) V) acid as a monoprotic acid), methyl orange, bromocresol green, or Congo red may be used as indicators. The secondary stage of phosphoric) V) acid is very weak (see acid Ka = 1 x 10 7 in Fig. 10.4) and the only suitable simple indicator is thymolphthalein (see Section 10.14) with phenolphthalein the error may be several per cent. A mixed indicator composed of phenolphthalein (3 parts) and 1-naphtholphthalein (1 part) is very satisfactory for the determination of the end point of phosphoric(V) acid as a diprotic acid (see Section 10.9). The experimental neutralisation curve of 50 mL of 0.1M phosphoric(V) acid with 0.1M potassium hydroxide, determined by potentiometric titration, is shown in Fig. 10.6. 

Discussion. For oils and fats, which are esters of long-chain fatty acids, the saponification value (or number) is defined as the number of milligrams of potassium hydroxide which will neutralise the free fatty acids obtained from the hydrolysis of 1 g of the oil or fat. This means that the saponification number is inversely proportional to the relative molecular masses of the fatty acids obtained from the esters. A typical reaction from the hydrolysis of a glyceride is ... 

In a titration, it was found that 28.5 cm3 of dilute nitric acid (concentration 0.100 mol dm-3) were exactly neutralised by 25.0 cm3 of potassium hydroxide solution. 

The bromide, [Co en2H20.0H]Br2.H20, is obtained from the chloride or from iraws-dichloro-diethylenediamino-cobaltic chloride by treating it with concentrated aqueous potassium hydroxide and, after cooling to 0° C., neutralising the solution obtained with concentrated hydrobromie acid. It is a red crystalline powder, and resembles the chloride in properties. 

The bromide, [Co en2H2O.OH]Br2, is obtained in a similar manner, or from the cis-salt by boiling the aqueous solution with potassium hydroxide for a short time and neutralising the solution with well-cooled hydrobromie acid. It is a light red powder, and is less soluble in water than the chloride. 

Dipyridino-palladic Chloride, [Pd py2]Cl4, is formed by the action of chlorine on dichloro-dipyridino-palladium suspended in chloroform. It crystallises in small orange-coloured prisms, and rapidly loses chlorine on exposure to moist air. If heated with potassium hydroxide a brown precipitate of palladic hydroxide separates, and if this is carefully neutralised with hydrochloric acid, potassium chloro-palladate crystallises out. Treatment with an aqueous solution of potassium iodide decomposes the salt, with formation of the palladous compound thus ... 

Lead arsenite is readily obtained by an electrolytic process.6 The eatholyte may be a 15 per cent, solution of sodium hydroxide or of a sodium salt, or a 30 per cent, solution of potassium hydroxide, the cathode being of nickel. The anolyte is a solution of an alkali arsenite neutralised towards phenolphthalein by means of acetic acid, and the anode is of lead. The cathode space is separated by a diaphragm of vegetable parchment. Ormont obtained a current yield of 97 per cent., and the average energy yield amounted to 1 kg. per kilowatt-hour. 

Potassium Metarsenite, KAs02, is obtained in an impure form when potassium carbonate and the above diarsenite are boiled together in aqueous solution for several hours.1 A syrupy mass is obtained. That the metarsenite should exist has been shown 2 by results obtained in measuring the effect of the progressive neutralisation of arsenious acid by potassium hydroxide on the freezing point of aqueous solutions. 

The pH value at which an arsenious sulphide sol flocculates infinitely slowly is approximately the same for different strong acids.4 Thus for a sol containing 1-55 g. AsaS3 per litre the pH was 1-22, but the value varies with the concentration of the sol. Weak acids fail to cause precipitation of the sol of the concentration mentioned with more concentrated sols weak acids cause precipitation, but the limiting pH shows a minimum value, less acid being required for very dilute and for very concentrated sols than for sols of intermediate concentrations. On dilution or neutralisation by potassium hydroxide, the pH value of an arsenious sulphide sol varies in a similar manner to the pH under similar conditions in the case of a weak acid, such as acetic acid, except that equilibrium is attained only after 1 to 3 days, indicating an evolution in the structure of the micelles. 

The methylacetanilide is boiled with concentrated alcoholic potash solution for about 24 hours in a reflux apparatus. The alcohol is distilled off, and the residue neutralised by addition of hydrochloric acid. The residual xylene is then distilled off in steam, the solution made alkaline, and the methylaniline steam distilled. It is taken up with ether, dried over anhydrous sodium sulphate or potassium hydroxide and fractionated. 

The saccharose solution to be inverted (containing one-half of the normal weight in about 75 c.c. of water) is mixed in a 100 c.c. flask with 5 c.c. of hydrochloric acid (sp. gr. 1 188), a thermometer being inserted in the flask and the latter placed in a water-bath at 70 °. After the temperature of the sugar solution reaches 67-70 it is maintained at this point for exactly 5 minutes, with frequent shaking the whole period of immersion in the bath never exceeds 10 minutes. The flask is subsequently cooled rapidly under the tap, the thermometer withdrawn and washed into the flask, and the solution neutralised almost completely with potassium hydroxide solution.1... 

Potassium sulphite solution is first prepared by saturating a solution of 10 grams of potassium hydroxide in 50 c.c. of water with sulphur dioxide in the cold and neutralising with powdered potassium carbonate (10 grams of potassium hydroxide and 50 c.c. of water require about 18 grams of potassium carbonate). 

Detection of Acetins.1—10 c.c. of the oil are shaken repeatedly with 40 c.c. of 10% alcohol, in which acetin is readily soluble and the oil practically insoluble after standing, the aqueous-alcoholic liquid is filtered through a filter moistened with the same alcohol. The oil and filter are washed with other small quantities of 10% alcohol, the alcoholic liquids being then evaporated on the water-bath to a small volume (5-10 c.c.). This residue is taken up in neutral alcohol, neutralised with N/10-potassium hydroxide (with phenolphthalein), and saponified with N/2-potasaum hydroxide, in the usual way, the volume of the alkali required for saponification being noted. 

What is the concentration of potassium hydroxide solution used in the following neutralisation reaction 20cm3 of 0.2 mol drrr3 solution of hydrochloric acid just neutralised 15 cm3 of potassium hydroxide solution. 

In a titration involving 24.0 cm3 potassium hydroxide solution against a solution containing 1 mol dm-3 of sulfuric acid, 28.0cm3 of the acid was found to just neutralise the alkali completely. 

In a neutralisation experiment, 25 cm3 of dilute sulfuric acid was required to react completely with 40 cm3 of a solution of 0.25 mol dm-3 potassium hydroxide. 

The chiral methoxyamine is recovered from the aqueous solution by neutralisation with solid potassium hydroxide and extraction with ether. The ethereal extract is washed with brine, dried over potassium carbonate and concentrated to give the crude chiral amine in 80-88 per cent yield. Distillation affords the pure amine (70-75% recovery) with [a] values which indicate that no racemisation has occurred. 

Methyl 4,6-O-benzyIidene-a-D-aItropyranoside. Triturate 4.0 g (0.015 mol) of the foregoing anhydro derivative in a mortar with a solution of 5 g of potassium hydroxide dissolved in 140 ml of water. Transfer the suspension to a round-bottomed flask and heat the mixture under reflux until all the solid has dissolved (about 28 hours). During this period solid material tends to creep up the inside of the flask surface shake periodically to re-suspend material. Remove the trace of insoluble matter which remains and neutralise the cooled filtrate with carbon dioxide (use phenophthalein as an indicator). Extract the solution with five 25 ml portions of dichloromethane, wash the combined extracts with a little cold water, dry over anhydrous sodium sulphate and remove the solvent under reduced pressure (rotary evaporator). Crystallise the syrup by scratching a small portion on a watch glass with ether stir the bulk syrup with ether and the seed crystals. Filter off and recrystallise the product from a small quantity of methanol to obtain 3.5 g (83%) of methyl 4,6-0-benzylidene-oc-D-altropyranoside, m.p. 174 °C, [a]D°+115° (c2 in CHCI3). 

Add 8.0g (10.0ml, 0.15 mol) of redistilled acrylonitrile (Expt 5.161, Note (1)) to a stirred solution of diethyl propylmalonate (30.2 g, 0.15 mol) (Expt 5.132) and of 30 per cent methanolic potassium hydroxide (4.0 g) in t-butyl alcohol (100 g). Keep the reaction mixture at 30-35 °C during the addition and stir for a further 3 hours. Neutralise the solution with 2 M-hydrochloric acid, dilute with water and extract with ether. Dry the ethereal extract with anhydrous sojdium sulphate and distil off the ether the residue [diethyl (2-cyanoethyl)-propylmalonate 11 g] solidifies on cooling in ice, and melts at 31—32 °C after recrystallisation from ice-cold ethanol. Boil the cyanoethyl ester (10 g) under reflux with 40 ml of 48 per cent hydrobromic acid solution for 8 hours, and evaporate the solution almost to dryness under reduced pressure. Add sufficient water to dissolve the ammonium bromide, extract several times with ether, dry the ethereal extract and distil off the solvent. The residual oil (4.5 g, 66%) soon solidifies upon recrystallisation from water, pure 2-propylglutaric acid, m.p. 70 °C, is obtained. 

Incidents of several different types have arisen from reactions involving neutralisation of an acid with a base where the exotherm (57.3 kJ/equivalent for strong acid—strong base reactions) has not occurred smoothly over an extended period, but has been sudden in effect for various reasons. Individually indexed neutralisation incidents are f Formaldehyde, Magnesium carbonate hydroxide, 0415 Potassium hydroxide, Acids, 4422 Sodium carbonate, 0549 Sulfuric acid, 4-Methylpyridine, 4473 Sulfuric acid, Diethylamine, 4473 2,4,6-Trichloro-l,3,5-triazine, 2-Ethoxyethanol, 1035 See related UNIT process or unit operation incidents... 

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