Extraction with Dilute Mineral Acid

Sperm heads are treated with dilute mineral acid (hydrochloric or sulfuric) (Kossel, 1929). By adding a solution of anion such as picrate to the acid extract, protamine is precipitated as an insoluble salt, which is further converted into sulfate or hydrochloride. In the original method of preparation of a protamine from testes of Rhine salmon, Miescher (1897) used 1—2 % hydrochloric acid for the extraction and platinum chloride for the precipitation of protamine. Kossel (1929) used 1 % sulfuric acid while Stedman and Stedman (1951) used 0.1—0.5 N sulfuric acid in their complete extraction procedure . Block et al. (1949) isolated the sulfate salt of clupeine and salmine on a larger scale, using 0.2 N hydrochloric acid and metaphosphate, respectively, as the extracting and precipitating reagents. 

Rasmussen s procedure (Rasmussen, 1934) which involves the extraction of sperm heads four times with 10-fold (v/w) volume of 0.2 N hydrochloric acid for 45 min at 0°C with subsequent addition of 1/8 M sodium picrate to precipitate the picrate salt of clupeine, was routinely used by the Tokyo group (Ando etal. 1957 Yamasaki, 1958). In this procedure, the risk of decomposition of both the protamine and DNA moieties is minimi2ed by the brevity of contact of the material with rather low concentrations of acid at low temperature. 

Protamine sulfate can easily be converted to the hydrochloride salt by the use of anion-exchange resins an aqueous solution of protamine sulfate is applied to a column packed with Amberlite IRA-400 (chloride form), the column is eluted with water and the effluent fractions containing protamine are lyophilized to give the hydrochloride salt (Ando et aL 1957 Yamasaki, 1958). By treating the picrate salt with 0.2 N hydrogen chloride-anhydrous methanol at room temperature, Felix s group obtained protamine methyl ester hydro-cloride salt (Rauen et aL 1952). 

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Separation of nitrogen compounds is difficult, and the compounds are susceptible to alteration and loss during handling. However, the basic low-molecular weight compounds may be extracted with dilute mineral acids. 

Assessing the relative importance of the various factors, which also has to include steric effects, is a complicated task. As already mentioned, nitrile formation in general is favored in these substitution reactions (equation 1), and as isonitriles are normally formed to only a very small extent, they can easily be removed by extraction with diluted mineral acids. 

The crude milled natural produet is usually moistened with an aqueous alkali, for instance Na2C03, NaHC03 or line so as to release the alkaloids from their respective salt and subsequently percolated with benzene, ether, or some other appropriate water-immiscible solvent. The solvent layer is extracted with dilute mineral acid to convert the alkaloids into their corresponding salts and also to push them into the aqueous phase. The free alkaloids may be precipitated by the addition of alkali and finally separated by suitable means. 

Vitamin B2 Food contains three B2 vitamers, riboflavin and its two coenzyme forms, flavin mononucleotide and flavin adenine dinucleotide, which are the predominant vitamers in foods and are usually bound to proteins. Their analysis usually takes place after extraction with dilute mineral acids with or without enzymatic hydrolysis of the coenzymes (which is necessary to convert all forms to riboflavin and to quantify them as total riboflavin). The extracts may be purified using SPE with Cig cartridges. All the operations performed prior to analysis need to be done under subdued lighting to avoid decomposition of riboflavin upon exposure to light. RP chromatography with Cig columns is used along with fluorescence detection (excitation, 440 nm emission, 520 nm). 

The cooled reaction mass is extracted from the retort, cmshed and leached first with dilute mineral acid, and then with water to separate the tantalum powder from the salts. After drying and classification, the primary powder is ready for processing to sheet, rod, wire, or capacitor-grade powder. 

Mix 1 g. of the nitro compound with 4 g. of sodium dichromate and 10 ml. of water in a 50 ml. flask, then attach a reflux condenser to the flask. Add slowly and with shaking 7 ml. of concentrated sulphuric acid. The reaction usually starts at once if it does not, heat the flask gently to initiate the reaction. When the heat of reaction subsides, boil the nnxture, cautiously at first, under refiux for 20-30 minutes. Allow to cool, dilute with 30 ml. of water, and filter off the precipitated acid. Purify the crude acid by extraction with sodium carbonate solution, precipitation with dilute mineral acid, and recrystallisation from hot water, benzene, etc. 

Isolation of products from the reductions with sodium borohydride is in the majority of cases much simpler. Since the reaction is carried out in aqueous or aqueous-alcoholic solution, extraction with ether is usually sufficient. Acidification of the reaction mixture with dilute mineral acids may precede the extraction. 

Elemental composition Cd 77.81%, S 22.91%. In crystalline state, it may be identified by x-ray diffraction measurement. In aqueous acid extract following digestion with nitric acid, cadmium may be measured by various instrumental techniques, (see Cadmium). Warming with dilute mineral acids liberates H2S, which may be identified by its odor or by browning of a white paper soaked in lead acetate solution. 

The reaction mixture is usually worked up by removing the basic solvent, if present, by extraction with dilute mineral add, solution of the residue in petroleum ether, and extraction with aqueous alkali to separate the phenolic product from any neutral by-products and unchanged ether. When the phenols are highly substituted, espedally the 2,6-disubstituted ones, their acidity may be so greatly diminished that they are practically insoluble in aqueous alkali Claisen s alkali (p. 28) has proved of great service in isolating weakly acidic phenols.11 101 Petroleum ether or benzene should be the solvent for the organic material when Claisen s alkali is used for an extraction. 

Dissolve the mixture in an organic solvent, and extract with a dilute aqueous solution of sodium hydroxide or sodium bicarbonate, which will neutralize benzoic acid. Naphthalene will remain in the organic layer, and all the benzoic acid, now converted to the benzoate salt, will be in the aqueous layer. To recover benzoic acid, remove the aqueous layer, acidify it with dilute mineral acid, and extract with an organic solvent. 

Atomic absorption spectroscopy has been used to determine the amount of impurities in talc samples based on the chemical composition [35]. The detection of calcium, iron, and aluminum gave an indication of the mineral and chemical purity of the talc, whereas, analyses for chromium, manganese, nickel, and copper were of toxicological interest. The sample preparation involved an acid extraction with dilute hydrochloric acid to remove magnesium and calcium carbonates. Total dissolution of the sample was achieved with nitric/hydrofluoric acid mixture, followed by nitric/perchloric acid mixtures. Calcium was determined in the nitrous oxide/acetyiene flame and the other elements were detected in the air/acetylene flame. 

The percentage extracted could be increased by repeating the experiment with dilute mineral acid replacing the buffer. Since the pKa of sulfamethoxazole is 5.6, carrying out the extraction at a pH of less than 2.6 (drug >99.9% unionised) will allow more of the drug to dissolve in the organic layer. 

One of the first comprehensive studies of the chemical nature of humic substances was carried out by Sprengel (1826, 1837). The procedures he developed for the preparation of humic acids became generally adopted, such as pretreatment of the soil with dilute mineral acids to enhance extraction with alkali. Sprengel concluded that, for soils rich in bases, humic acid was in a bound form consequently, the soil had a neutral reaction (contained mild humus ). This soil was regarded as highly fertile. On the other hand, for soils poor in bases, the humic acid was believed to be in the free form, with the result that the soil was acid and unproductive (contained acid humus ). A major contribution of Sprengel to humus chemistry was his extensive studies on the acidic nature of humic acids. 

However it has been stated by many authors that a more efficient extraction is obtained by first treating the seaweed with dilute mineral acid ... 

Calcination causes some oxidation of the product, resulting in the formation of soluble cadmium sulfate. Prevailing regulations require pigments or pigmented articles to pass tests for the extraction of heavy metals. In order to meet these tests any soluble cadmium must first be removed. This is achieved by acidification with dilute mineral acid, followed by decant /washing of the fired slurry, or filtration and washing by some other means. 

During the first part of the nineteenth century considerable attention was paid to the chemistry of humic substances. A detailed description of the analysis of humic acid with particular reference to its acidic properties was given by Sprengel. One of his innovations still in vogue today was the pretreatment of soil with dilute mineral acid prior to its extraction with alkali. Sprengel also observed that after removal of all the mineral acid, freshly precipitated humic acid partially dissolved in cold water, but after drying, the humic material was converted into a less water-soluble form for which the term humus coal was proposed. 

Vanadium usually is recovered from its ores by one of two processes, (1) leaching raw mineral with hot dilute sulfuric acid, and (2) roasting ore with common salt to convert vanadium into water soluble sodium vanadates. In the sulfuric acid leaching process, vanadium is extracted from acid leach liquors by solvent extraction with an aliphatic amine or an alkyl phosphoric acid in kerosene. The organic solvent extract then is treated with an aqueous solution of ammonia in the presence of ammonium chloride to convert vanadium into ammonium metavanadate. Alternatively, the organic extract is treated with dilute sulfuric acid or an aqueous solution of soda ash under controlled conditions of pH. Vanadium is precipitated from this solution as a red cake of sodium polyvanadate. 

In 1839 Mosander heated some cerium nitrate and treated tire partly decomposed salt with dilute nitric acid. In the extract he found a new earth, which he named lanthana, meaning hidden, meanwhile retaining the old name, ceria, for the oxide which is insoluble in dilute nitric acid (7, 28, 45). In the same year, Axel Erdmann, one of Sefstrom s students, discovered lanthana in a new Norwegian mineral, which he named mosan-drite in honor of Mosander. 

The salts of the series are bright red crystalline bodies. They are soluble in water, neutral in reaction, and dilute mineral acids do not transform them into aquo-salts. The least soluble member of the series is the sulphate [(NH3)4Co (OH)2 Co(NH3)4](S04)a.2H30, which is prepared by heating hydroxo-aquo-tetrammino-cobaltic sulphate at 100° C. till it is constant in weight. The mass is extracted with water and the sparingly soluble sulphate collected and dried. The crude product so obtained is converted into the chloride and an aqueous solution of this then treated with a solution of sodium sulphate, when a crystalline precipitate of the diol-sulphate is obtained. It is collected, washed with water, alcohol, and finally with ether. It forms small red needle-shaped crystals which contain two molecules of water of hydration. 

Due to their extremely polar character, tetracyclines bind with proteins to form conjugates that are difficult to extract from biological matrices. Use of dilute mineral acids is of great help in dissociating tetracyclines from proteins, but once in aqueous solution, their exfraction into volatile organic solvents for further concentration and cleanup is hampered by the unfavorable partition coefficients. Most of these antibiotics are photosensitive compounds, whereas all of them show poor stability under strong acidic and alkaline conditions with reversible formation of the 4-epi-tetracyclines in weakly acidic conditions (pH 3), and anhydro-tetracyclines in strong acidic conditions (below pH 2). 

Various microchemical tests are available for the detection of minute quantities of sulphur, both free and combined. The substance under examination may be treated with a little sodium hydroxide solution, the extract evaporated just to dryness, a few drops of aqueous sodium cyanide (0-1 per cent.) added and the evaporation repeated. The residue, moistened with dilute sulphuric acid and a drop of ferric chloride, gives the characteristic ferric thiocyanate colour if sulphur is present.6 In the ease of minerals, traces of sulphur dioxide produced on heating may be detected 6 by the colour change of an alkaline solution of Bromocrcsol Green or by the deeolorisation of starch-iodine solution. 

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