Alcoholic-hydrochloric acid standardization

Addition tube, 20, 21 Alanine, /3-(3,4-dihydroxyphenyl)-N-METHYL-, 22, 89, 91 Alcoholic hydrochloric acid, 22, 77, 83 standardization, 22, 80 Alcoholysis, 20, 67 Aldehyde synthesis, 20, 14 from acid chlorides by Rosenmund reaction, 21, 84, 87, 88, 110 Alkylation of thiourea, 22, 59 Alkylchlororesorcinols, 20, 59 Alkylene bromide, 20, 24 S-Alkylthiuronium halides, 22, 60 dl-ALLOTHREONINE, 20, 10 ... 

For analysis of acids, esters, alcohols, ketones, aldehydes and fiirfiual the test solution was prepared by dilution of a weighed sam de of clear ftaction of the condensate 10 g to 100 ml with distillate water. The content of acids and esters was determined by potentiometric titration, using potassium hydroxide and hydrochloric acid standard volumetric solutions. c(KOH) = 0.1 mol/l c(HCl) = 0.1 molfi. An automatic potentiometric titration assembly RTS - 822 Radiometer (Denmark) was used. 

Obtain an unknown mixture from your instructor. The mixtures to be separated will contain approximately 1 mg of each amino acid per milliliter 0.5 M alcoholic hydrochloric acid solution (see discussion below). Spot approximately 1 /u,L of the sample solution on the Chromagram sheet about 2 cm from the lower edge. (Activation of the sheet is not necessary for this separation.) The unknown should contain acids whose Rf values are sufficiently different with the solvent system used so that they will be readily separated. Your instructor will advise you which standard amino acid solutions to run with your unknown so that you can distinguish between two amino acids that might have an value close to one in your mixture. Allow 15 to 20 min drying to ensure complete evaporation of the hydrochloric acid. 

The standard manufacturing method for tetraalkyl titanates, such as TYZOR TPT, or tetra- -butyi titanate, TYZOR TBT [5593-70 ] involves the addition of TiCl to an alcohol. In a series of reversible displacement reactions, the alkoxy substitution products and hydrochloric acid form as follows ... 

One 1-ml aliquot is added to 1.0 ml of freshly-distilled 1,2-dibromo-ethane (bp 132°C) in an oven-dried flask which contains a static atmosphere of nitrogen or argon. After the resulting solution has been allowed to stand at 25°C for 5 min, it Is diluted with 10 rat of water and titrated for base content (residual base) to a phenolphthalein endpoint with standard 0.100 M hydrochloric acid. The second 1-mL aliquot is added cautiously to 10 ml of water and then titrated for base content (total base) to a phenol phthalein endpoint with standard aqueous 0.100 M hydrochloric acid. The methyllithium concentration is the difference between the total base and residual base concentrations.2 Alternatively, the methynithiura concentration may be determined by titration with a standard solution of sec-butyl alcohol employing 2,2 -bipyridyl as an indicator. 

A solution of dry ammonia gas in absolute ethyl alcohol is prepared and titrated against standard hydrochloric acid, using methyl orange as the indicator. The solution should contain at least 9 per cent of ammonia by weight (Note 5). 

The saponification number expresses the amount of base that will react with 1 g of a sample when heated in a specific manner. Since certain elements are sometimes added to asphalt and also consume alkali and acids, the results obtained indicate the effect of these extraneous materials in addition to the saponifiable material present. In the test method (ASTM D94 IP 136), a known weight of the sample is dissolved in methyl ethyl ketone or a mixture of suitable solvents, and the mixture is heated with a known amount of standard alcoholic potassium hydroxide for between 30 and 90 minutes at 80°C (176°F). The excess alkali is titrated with standard hydrochloric acid and the saponification number is calculated. 

The assay method involves the reaction of benzaldehyde with hydroxylamine hydrochloride in an alcoholic solution. Benzaldehyde oxime, water, and hydrochloric acid are the products of the reaction. The hydrochloric acid formed is then titrated with standard caustic solution to determine the benzaldehyde assay. 

With such an experiment as is described above, using 1000 g. of absolute alcohol in the solvent flask and about 150 g. in the end Wolff bottle, 1469 g. of solution are obtained in the main flask and 174 g. in the Wolff bottle, thus indicating that a total of 491 g. (89 per cent theory) of trimethylamine are present. There is thus obtained a 32 per cent solution in the main flask which has a sp. gr. of about 0.760 at +50. By titration with standard hydrochloric acid, the same amounts of trimethylamine are indicated, as are found by weighing. In several experiments, the yields were consistently 85-90 per cent of the theory. 

The saponification value is the amount of alkali required to saponify a defined amount of sample. It is expressed in mg potassium hydroxide (KOH) per g sample. The procedure involves the use of excess alcoholic KOH, which catalyzes the saponification/release of the free fatty acids from the glycerol backbone. The unreacted KOH is then back-titrated with standardized hydrochloric acid (HC1) using phenolphthalein as the indicator. The amount and normality of the HC1 used for neutralization can then be used to calculate the saponification value. The saponification value provides evidence as to the relative chain lengths of the fatty acids in the system. 

By hydrolysis with standard alcoholic potash (p. 509). A quantity, 1—2 gms., of the ester is placed in a flask containing 50 c.cs. of semi-normal alcoholic potash. The flask is fitted with a reflux condenser, and the mixture boiled on a water bath for 2—3 hours until hydrolysis is complete. A little water is then run down the inner surface of the condenser into the flask, and the excess of potash in the flask titrated with standard hydrochloric acid, using phenolphthalein as indicator. The quantity of potash used in the hydrolysis gives a measure of the value of the ester. 

In the determination, 2 g of the diisocyanate should be accurately weighed out into a conical flask and 5 ml of chlorobenzene added. In the case of naphthalene diisocyanate, it is recommended that the mixture be warmed slightly to assist dissolution. To this mixture there is then added 25 ml of the standard dibutylamine solution. The reaction is rapid and takes only a few minutes for completion, when a clear solution is obtained. After adding 2 or 3 drops of a 1% alcoholic solution of bromophenol blue and 100 ml of methanol, the excess dibutylamine can be titrated with 1 N hydrochloric acid. 

This can be prepared in several different ways. Commonly dry Castile soap is dissolved in 80 per cent, alcohol in such proportions as will yield a solution well above the desired final concentration 100 grams per litre is a convenient ratio. After allowing this solution to stand at rest for several days for the deposition of undissolved matter, a quantity of the clear liquid is withdrawn (usually 75-100 c.c. per litre of final solution), and so diluted with 80 per cent, alcohol as to produce a solution which on titration with a known weight of calcium chloride solution under the standard conditions will give results in accordance with Clark s table. The calcium chloride solution is best prepared by dissolving 0-2 grams of Iceland spar in dilute hydrochloric acid excess of acid is removed by evaporation on a water bath and the solution then diluted to 1 litre with distilled water. A mixture of 25 c.c. of this solution, mixed with 25 c.c. of water, should require 7-8 e.e. of Clark s standard solution for the production of a permanent lather. 

THI-DNPH Standard Add 0.5 g of DNPH Hydrochloride to 1 mL of hydrochloric acid, followed by 10 mL of ethyl alcohol, and heat on a steam bath until solution. Add 100 mg of THI to the hot solution—crystallization begins in a few minutes. Filter off the THI-DNPH when the suspension reaches room temperature. Obtain the THI-DNPH Standard by recrystallizing the THI-DNPH with a hydrochloric acid-ethyl alcohol mixture (1 drop of hydrochloric acid per 5 mL of ethyl alcohol). The yield is 70% to 80% based on the THI used. When stored in the refrigerator, the THI-DNPH Standard is stable for at least 1 year. 

Potassium Hydroxide, 0.5 N, Alcoholic (Caution The solution may become very hot. Allow it to cool before adding the aldehyde-free alcohol.) Dissolve about 35 g of potassium hydroxide (KOH) in 20 mL of water, and add sufficient aldehyde-free alcohol to make 1000 mL. Allow the solution to stand in a tightly stoppered bottle for 24 h. Then quickly decant the clear supernatant liquid into a suitable, tight container, and standardize as follows Transfer quantitatively 25 mL of 0.5 N hydrochloric acid into a flask, dilute with 50 mL of water, add 2 drops of Phenolphthalein TS, and titrate with the alcoholic potassium hydroxide solution until a permanent, pale pink color is produced. Calculate the normality. Store this solution in tightly stoppered bottles protected from light. 

Although consumption of the hydroperoxide is normally complete, the absence of this peroxide in the reaction mixture should be established by testing with moist starch-iodide paper or by iodometric titration.2 The amine oxide content may be determined by titration with standard aqueous hydrochloric acid after any amine present has been consumed by reaction with methyl iodide for 1 hour at room temperature.3 From this volumetric analysis the submitters determined the yield of amine oxide to be 86%. The checkers found that the reaction could be followed by measuring the n.m.r. spectra in -butyl alcohol solution where the n.m.r. N-methyl signals of the amine (at S 2.03) and the amine oxide (at S 2.98) are readily observed. 

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