Hydrochloric medium concentrated

The medium is most often acidihed with hydrochloric acid (0.1% vNY but it should be noted that in light of the work of Revilla et al., the hydrochloric acid concentration should not exceed 0.12 mole/liter to prevent risks of anthocyanidin hydrolysis. Formic acid (2% v/v), with a greater volatility than hydrochloric acid, is preferred because it prevents risks of hydrolysis during the extract concentration stage. ... 

III.5 MERCURY, Hg (A, 200-59) - MERCURY Mercury is a silver-white, liquid metal at ordinary temperatures and has a density of 13 534 g ml-1 at 25°C. It is unaffected when treated with hydrochloric or dilute sulphuric acid (2m), but reacts readily with nitric acid. Cold, medium concentrated (8m) nitric acid with an excess of mercury yields mercury ions ... 

III.10 COPPER, Cu (Ar 63-54) Copper is a light-red metal, which is soft, malleable, and ductile. It melts at 1038°C. Because of its positive standard electrode potential (+0- 34 V for the Cu/Cu2+ couple) it is insoluble in hydrochloric acid and in dilute sulphuric acid, although in the presence of oxygen some dissolution might take place. Medium-concentrated nitric acid (8m) dissolves copper readily ... 

This is not surprising since °(Cl2(g)/CD) = 1.36 V. As a result, permanganate ions are consumed in excess. However, in some concentration conditions, the latter reaction may be minimized and may even be negligible. Hence, there exist titrations such as those of As+ Sb+ and HgOg that can be achieved in a hydrochloric medium. In principle, nitric acid is convenient, but it may contain nitrites and nitrous derivatives, which are reducing agents. For this reason, its use must be avoided. 

In this method, monomer (aniline) is synthesized in aqueous solution containing oxidant, for example, ammonium peroxydisulfate and acid, for example, hydrochloric. In this type of synthesis, the monomer is converted directly to conjugated polymer by a condensation process. However, an excess of the oxidant lead to materials that are essentially intractable is one of its disadvantages. By progressing the oxidative condensation of aniline, the color of solution turns to black which probably is due to the soluble oligomers. The nature of the medium and the concentration of ihe oxidant are the effective parameters on the intensity of coloration. The major effective parameters on the course of the reaction and on the nature of Ihe final product are as follows nature and temperature of medium, concentration of the oxidant, and duration of the reaction. To obtain desirable results, some factors as low ionic strength, volatility, and non-corrosive nature of the medium should be controlled although no medium satisfies all of these requirements [27]. 

Prepare a solution of 41 g. of anhydrous palladium chloride (1) in 10 ml. of concentrated hydrochloric acid and 25 ml. of water (as in A). Add all at once 60 ml. of 6iV-sulphuric acid to a rapidly stirred, hot (80°) solution of 63 1 g. of A.R. crystallised barium hydroxide in 600 ml. of water contained in a 2-htre beaker. Add more 6iV-sulphuric acid to render the suspension just acid to htmus (5). Introduce the palladium chloride solution and 4 ml. of 37 per cent, formaldehyde solution into the hot mechanically stirred suspension of barium sulphate. Render the suspension slightly alkaline with 30 per cent, sodium hydroxide solution, continue the stirring for 5 minutes longer, and allow the catalyst to settle. Decant the clear supernatant hquid, replace it by water and resuspend the catalyst. Wash the catalyst by decantation 8-10 times and then collect it on a medium - porosity sintered glass funnel, wash it with five 25 ml. portions of water and suck as dry as possible. Dry the funnel and contents at 80°, powder the catalyst (48 g.), and store it in a tightly stoppered bottle. 

After evaporation of the solvent, the solid residue consists of 5-(2-chlorobenzyl)-thieno[3,2-cl -pyridinium chloride which melts at 166°C (derivative n°30). This compound is taken up into a solution comprising ethanol (300 ml) and water (100 ml). Sodium borohydride (NaBH4) (20 g) is added portionwise to the solution maintained at room temperature. The reaction medium is maintained under constant stirring during 1 2 hours and is then evaporated. The residue is taken up into water and made acidic with concentrated hydrochloric acid to destroy the excess reducing agent. The mixture is then made alkaline with ammonia and extracted with ether. The ether solution is washed with water, dried and evaporated. The oily residue is dissolved in isopropanol (50 ml) and hydrochloric acid in ethanol solution is then added thereto. 

After dissolution of the alloy in a mixture of concentrated nitric and hydrochloric acids the iron is masked with triethanolamine in an alkaline medium, and the manganese titrated with standard EDTA solution using thymolphthalexone as indicator. The amount of iron(III) present must not exceed 25 mg per 100 mL of solution, otherwise the colour of the iron(III)-triethanolamine complex is so intense that the colour change of the indicator is obscured. Consequently, the procedure can only be used for samples of ferro-manganese containing more than about 40 per cent manganese. 

Determination of silver as chloride Discussion. The theory of the process is given under Chloride (Section 11.57). Lead, copper(I), palladium)II), mercury)I), and thallium)I) ions interfere, as do cyanides and thiosulphates. If a mercury(I) [or copper(I) or thallium(I)] salt is present, it must be oxidised with concentrated nitric acid before the precipitation of silver this process also destroys cyanides and thiosulphates. If lead is present, the solution must be diluted so that it contains not more than 0.25 g of the substance in 200 mL, and the hydrochloric acid must be added very slowly. Compounds of bismuth and antimony that hydrolyse in the dilute acid medium used for the complete precipitation of silver must be absent. For possible errors in the weight of silver chloride due to the action of light, see Section 11.57. 

The kinetics of desulphonation of sulphonic acid derivatives of m-cresol, mesitylene, phenol, p-cresol, and p-nitrodiphenylamine by hydrochloric or sulphuric acids in 90 % acetic acid were investigated by Baddeley et a/.701, who reported (without giving any details) that rates were independent of the concentration of sulphuric acid and nature of the catalysing anion, and only proportional to the hydrogen ion concentration. The former observation can only be accounted for if the increased concentration of sulphonic acid anion is compensated by removal of protons from the medium to form the undissociated acid this result implies, therefore, that reaction takes place on the anion and the mechanism was envisaged as rapid protonation of the anion (at ring carbon) followed by a rate-determining reaction with a base. 

The addition of water and a non-hydrogen-bonding solvent to the reduction medium causes the reactions to shift toward the formation of alcohol products.313 For example, triethylsilane in a mixture of concentrated hydrochloric acid and acetonitrile (5 4) reduces 1-heptanal to 1-heptanol in quantitative yield after 3 hours at room temperature. In a mixture of triethylsilane in sulfuric acid, water, and acetonitrile (2 2 5), //-hep(anal gives a 97% yield of the same alcohol after 1.25 hours (Eq. 156).313... 

Moore [355] used the solvent extraction procedure of Danielson et al. [119] to determine iron in frozen seawater. To a 200 ml aliquot of sample was added lml of a solution containing sodium diethyldithiocarbamate (1% w/v) and ammonium pyrrolidine dithiocarbamate (1 % w/v) at pH to 4. The solution was extracted three times with 5 ml volumes of 1,1,2 trichloro-1,2,2 trifluoroethane, and the organic phase evaporated to dryness in a silica vial and treated with 0.1 ml Ultrex hydrogen peroxide (30%) to initiate the decomposition of organic matter present. After an hour or more, 0.5 ml 0.1 M hydrochloric acid was added and the solution irradiated with a 1000 W Hanovia medium pressure mercury vapour discharge tube at a distance of 4 cm for 18 minutes. The iron in the concentrate was then compared with standards in 0.1 M hydrochloric acid using a Perkin-Elmer Model 403 Spectrophotometer fitted with a Perkin-Elmer graphite furnace (HGA 2200). 

Sulfuric acid as a reaction medium may be replaced by glacial acetic acid or by a mixture of glacial acetic acid/nitrosylsulfuric acid. In the former case, half-concentrated hydrochloric acid is added, and diazotization proceeds in an aqueous sodium nitrite solution. The combination of glacial acetic acid/nitrosylsulfuric acid is a particularly useful medium for the bisdiazotization of 1,2-, 1,3-, or 1,4-di-aminobenzenes (phenylenediamines). 

Co-precipitation of Re S with platinum sulfide from cone, hydrochloric acid solutions of microamounts of technetium and rhenium is suitable for the separation of technetium from rhenium , since technetium is only slightly co-precipitat-ed under these conditions (Fig. 7). At concentrations of 9 M HCl and above, virtually no technetium is co-precipitated with platinum sulfide at 90 °C, whereas rhenium is removed quantitatively even up to 10 M HCl. The reduction of pertechnetate at high chloride concentration may be the reason for this different behavior, because complete co-precipitation of technetiiun from sulfuric acid solutions up to 12 M has been observed. However, the separation of weighable amounts of technetium from rhenium by precipitation with hydrogen sulfide in a medium of 9-10 M HCl is not quantitative, since several percent of technetiiun coprecipitate with rhenium and measurable amounts of rhenium remain in solu-tion . Multiple reprecipitation of Re S is therefore necessary. 

These elements are noble metals and, as such, can be dissolved only with great difficulty. The usual leaching agent is hydrochloric acid, with the addition of chlorine to increase the solution oxidation potential. This strong chloride medium results in the almost exclusive formation of aqueous chloroanions, with, under certain circumstances, the presence of some neutral species. Very seldom are cationic species formed in a chloride medium. However, these elements do possess a range of easily accessible oxidation states and, with the possibility of a number of different anionic complexes that are dependent on the total chloride concentration, this provides a very complicated chemistry. A summary of the most important chloro complexes found in these leach solutions is given in Table 11.6, from which the mixed aquochloro and polynuclear species have been omitted. The latter are found especially with the heavier elements. 

TeCl4 in concentrated hydrochloric acid reacts with arenediazonium chlorides giving bis(arenediazonium) hexachlorotellurates that are decomposed by copper powder in acetone to give diaryltellurium dichlorides in low to medium yields. ... 

Iron was one of the first metals employed for the reduction of organic compounds over 130 years ago. It is used in the form of filings. Best results are obtained with 80 mesh grain [765]. Although some reductions are carried out in dilute or concentrated acetic acid the majority are performed in water in the presence of small amounts of hydrochloric acid, acetic acid or salts such as ferric chloride, sodium chloride (as little as 1.5-3%) [765], ferrous sulfate [766] and others. Under these conditions iron is converted to iron oxide, Fe304. Methanol or ethanol are used to increase the solubility of the organic material in the aqueous medium [766] (Procedure 34, p. 213). 

The bomb contents are digested with concentrated hydrochloric acid, and material still undissolved is then digested with potassium hydroxide and hydrogen peroxide. A crude separation is made by a sulfide precipitation from the combined digestion solutions. The sulfides are dissolved in aqua regia, the solution is evaporated, and antimony in the residue is reduced to antimony (III) with hydroxylamine hydrochloride. The sample, in ammonium thiocyanate-hydrochloric acid medium, is loaded onto a Dowex 2 column (SCN" form). Arsenic and other impurities are eluted with aliquots of more dilute ammonium thiocyanate-hydrochloric acid solutions. Antimony is eluated with sulfuric acid and fixed in solution by addition of hydrochloric acid. The activity of the solution caused by the 0.56 MeV y-ray of 2.8-day 122Sb is counted. 

Molten salts provide a medium in which the concentration of anionk/ligands can be much higher than is possible in aqueous solutions. The concentration of the chloride ion in concentrated aqueous hydrochloric acid is about 12 M. for example. In contrast,... 

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