Acidifying agents hydrochloric acid

As an acidifying agent, hydrochloric acid was formerly used for silage production, although nowadays this role is much reduced and defense against infectious diseases is much more prominent. A comparable indication is covered by calcium hydroxide, which is used traditionally as a paint in stables and has a disinfectant capability. 

A stereoselective GC method for determination of etodolac enantiomers in human plasma and urine was first reported as a preliminary method [35], and then as a validated method [36]. Sample preparation involved addition of (S)-(+)-naproxen (internal standard) and sodium hydroxide to diluted plasma or urine. The samples were washed with diethyl ether, acidified with hydrochloric acid, and extracted with toluene. ( )-(+)-naproxen was used as a derivatizing agent to form diastereomeric derivatives of etodolac. The gas chromatograph system used in this work was equipped with fused-silica capillary column (12 m x 0.2 mm i.d.) coated with high-performance cross-linked methylsilicone film (thickness 0.33 pm) and a nitrogen-phosphorous detector. The operating conditions were injector 250°C detector 300°C column 100-260°C (32 °C/min). 

Test for periodate (see note 1 below) This anion will give a positive test for oxidizing agents, but will not be detected in the systematic analysis. It will be necessary to remove first iodide or iodate by precipitation with silver nitrate in acid solution, and the excess silver ions with sodium chloride solution the resulting solution is strongly acidified with hydrochloric acid and an iron(II) salt is added. If a periodate is present, it will be reduced to iodine, which can be identified with carbon tetrachloride. 

In most procedures the acid is neutralized when hydrolysis has reached a desired stage. An electrolytic process for the removal of acid has been reported.124 It was found that isostatic processing of starch was faster with starch acidified with hydrochloric acid.125-127 Pre-hydrolysis of starch for further hydrolysis with milder hydrolyzing agents, such as sulfur dioxide, might also be of some benefit.128129... 

To a mixture of 10 g. of the compound and 3-5 ml. of 33 per cent, sodium hydroxide solution in a test-tube, add 2-5 ml. of 50 per cent, chloroacetic acid solution. If necessary, add a little water to dissolve the sodium salt of the phenol. Stopper the test-tube loosely and heat on agently-boiling water bath for an hour. After cooling, dilute with 10 ml. of water, acidify to Congo red with dilute hydrochloric acid, and extract with 30 ml. of ether. Wash the ethereal extract with 10 ml, of water, and extract the aryloxyacetic acid b shaking with 25 ml. of 5 per cent, sodium carbonate solution. Acidify the sodium carbonate extract (to Congo red) with dilute hydrochloric acid, collect the aryloxyacetic acid which separates, and recrystallise it from hot water. 

The residue is dissolved in 300 ml. of water. The solution is poured onto 200 g. of ice and acidified to a pH of about 4 by addition of 75 ml. of 10% hydrochloric acid. The resulting mixture is extracted with four 100-ml. portions of peroxide-free ether, and the combined extracts are washed with 50 ml. of a saturated aqueous solution of sodium chloride and dried over 2 g. of anhydrous magnesium sulfate (Note 2). The ether solution is separated from the drying agent and concentrated at room temperature under reduced pressure. The residual oil is distilled from a 25-ml. 

A previously reviewed method was applied for OTC, TC, CTC, DXC, and DMC analysis in tissue and egg samples however, further optimization and improvement were necessary. The optimal recoveries from tissue were obtained using succinate buffer and MeOH as a depro-teinization agent. The eluate from the MCAC column was acidified and further purified on an Empore disk equipped with a poly(styrene-divinylbenzene)-RP sulphonated membrane previously activated with MeOH and hydrochloric acid (pH 1.0). The elution of TCs was done with methanolic ammonia solution. The extract was evaporated under vacuum and reconstituted in oxalic acid solution. Even though the stability of TCs is poor under alkaline conditions, no influence on the recovery was observed (59-76% with RSD < 6.5% for kidney samples) (26). 

A mixture of 5 g of aluminum amalgam, 5 g of acetoacetic acid p-phenetidide and 50 ml of ethanol are gently heated for 30 minutes. After filtering off the reducing agent with suction, water is added to the filtrate, and the latter is then acidified with 2 N hydrochloric acid. p-Hydroxybutyric acid p-phenetidide melting at 160°C crystallizes in almost quantitative yield in the form of white crystals. 

A mixture of 34.4 g (100 mmol) 5-benzoyl-N-methyl-N-phenyl-2,3-dihydro-lH-pyrrolizine-l-carboxamide, 25 g sodium hydroxide in 25 mL water, and 80 mL methanol was refluxed for 5 hours. The mixture was cooled to room temperature, stirred under nitrogen for sixteen hours, and then diluted with 80 mL of water. The mixture was extracted with toluene, and the aqueous and organic phases were separated. The aqueous phase was acidified with 6 N hydrochloric acid. The resulting precipitate was extracted with dichloromethane. The combined extract was treated with activated clay decolorizing agent (4.5 g) for 30 minutes, filtered, and concentrated by... 

Reducing agents, e.g. zinc, tin(II) chloride solution, colour a molybdate solution acidified with dilute hydrochloric acid blue (probably due to Mo3+), then green and finally brown. 

Hydrochloric acid is widely used as an acidifying agent, in a variety of pharmaceutical and food preparations (see Section 16). It may also be used to prepare dilute hydrochloric acid, which in addition to its use as an excipient has some therapeutic use, intravenously in the management of metabolic alkalosis, and orally for the treatment of achlorhydria. See Section 17. 

In pharmaceutical formulations, dilute hydrochloric acid is usually used as an acidifying agent in preference to hydrochloric acid. Hydrochloric acid is also used therapeutically as an escharotic. The PhEur 2005 also contains a specification for hydrochloric acid, dilute see Section 17. 

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