Hydrochloric diluted

Silver is a white, malleable, and ductile metal. It has a high density (10.5gmr ) and melts at 960.5°C. It is insoluble in hydrochloric, dilute... 

Usually prepared by the action of NaCN on benzaldehyde in dilute alcohol. It is oxidized by nitric acid to benzil, and reduced by sodium amalgam to hydrobenzoin PhCHOHCHOHPh by tin amalgam and hydrochloric acid to des-oxybenzoin, PhCH2COPh and by zinc amalgam to stilbene PhCH = CHPh. It gives an oxime, phenylhydrazone and ethanoyl derivative. The a-oxime is used under the name cupron for the estimation of copper and molybdenum. 

CHi=CMeCOOH. Colourless prisms m.p. 15-16 C, b.p. 160-5 C. Manufactured by treating propanone cyanohydrin with dilute sulphuric acid. Polymerizes when distilled or when heated with hydrochloric acid under pressure, see acrylic acid polymers. Used in the preparation of synthetic acrylate resins the methyl and ethyl esters form important glass-like polymers. 

Germanium, however, does not react with either dilute sulphuric or dilute hydrochloric acid, unlike tin, the next element in the group. 

Tin slowly dissolves in dilute hydrochloric, nitric and sulphuric acids, and is in fact the only Group IV element to do so. The reactions with more concentrated acid are rapid. With hydrochloric acid. 

Lead reacts only briefly with dilute hydrochloric and sulphuric acids for both lead(Il) chloride and lead(Il) sulphate are insoluble and form a film on the lead which effectively prevents further attack. Lead, however, does slowly dissolve in both concentrated sulphuric and hydrochloric acids. The sulphuric acid is reduced to sulphur dioxide ... 

If a dilute acid is added to this solution, a white gelatinous precipitate of the hydrated tin(IV) oxide is obtained. It was once thought that this was an acid and several formulae were suggested. However, it now seems likely that all these are different forms of the hydrated oxide, the differences arising from differences in particle size and degree of hydration. When some varieties of the hydrated tin(IV) oxide dissolve in hydrochloric acid, this is really a breaking up of the particles to form a colloidal solution—a phenomenon known as peptisation. 

Hydrochloric and dilute sulphuric acids have no appreciable action at room temperature on the pure Group V elements. 

Sulphur can be reduced directly to hydrogen sulphide by passing hydrogen through molten sulphur the reversible reaction H2 -I-S H2S occurs. In the laboratory the gas is most conveniently prepared by the action of an acid on a metal sulphide, iron(II) and dilute hydrochloric acid commonly being used ... 

This has been made in trace quantities by the action of dilute hydrochloric acid on magnesium plated with polonium. As expected, it is extremely unstable and decomposes even at 100 K,... 

Barium sulphite is soluble in dilute hydrochloric acid unlike barium sulphate which is insoluble. Hence this reaction, and the evolution of sulphur dioxide on addition of an acid, distinguishes a sulphite from a sulphate. 

Hydrochloric acid is a strong monobasic acid, dissolving metals to form salt and evolving hydrogen. The reaction may be slow if the chloride formed is insoluble (for example lead and silver are attacked very slowly). The rate of attack on a metal also depends on concentration thus aluminium is attacked most rapidly by 9 M hydrochloric acid, while with other metals such as zinc or iron, more dilute acid is best. 

Electrolysis of hydrochloric acid yields hydrogen at the cathode and oxygen at the anode from the dilute acid, but chlorine at the anode (of carbon) from the concentrated acid. Electrolysis of the concentrated acid is used on the large scale to recover chlorine. 

Manganese(IV) oxide is a dark-brown solid, insoluble in water and dilute acids. Its catalytic decomposition of potassium chlor-ate(V) and hydrogen peroxide has already been mentioned. It dissolves slowly in alkalis to form manganates(lW), but the constitution of these is uncertain. It dissolves in ice-cold concentrated hydrochloric acid forming the complex octahedral hexachloromangan-ate(IV) ion ... 

The anhydrous chloride is prepared by standard methods. It is readily soluble in water to give a blue-green solution from which the blue hydrated salt CuClj. 2H2O can be crystallised here, two water molecules replace two of the planar chlorine ligands in the structure given above. Addition of dilute hydrochloric acid to copper(II) hydroxide or carbonate also gives a blue-green solution of the chloride CuClj but addition of concentrated hydrochloric acid (or any source of chloride ion) produces a yellow solution due to formation of chloro-copper(ll) complexes (see below). 

When titanium dissolves in dilute hydrochloric acid, a violet solution containing titanium(III) ions is formed. This solution rapidly decolorises acidified aqueous potassium permanganate at room temperature. Titanium(IV) chloride is a colourless covalent liquid completely hydrolysed by water. Titanium(III) chloride forms hydrated titanium(III) ions in water and disproportionates when heated in a vacuum. 

Meanwhile assemble the apparatus shown in Fig. 62, or that in Fig. 23(D), p. 45, having a distilling-flask of at least 500 ml. capacity in either case. If an ordinary condenser C (Fig. 62) is employed, fit the lower end of the condenser by means of a short piece of rubber tubing to a small inverted funnel. Arrange the latter so that its lip is just below the surface of 25 ml. of concentrated hydrochloric acid diluted with 75 ml. of water contained in a 250 ml. beaker B the hydro-. chloric acid is thereby prevented from being sucked back into the... 

Disconnect the column, and remove the flask from the oil-bath. Add 25 ml. of dilute hydrochloric acid to the flask, shake the contents vigorously, and chill in ice-water, when crystals of benzhydrol will separate. (Occasionally the hydrol will separate initially as an oil, which ciystallises on vigorous stirring.)... 

SULPHANILAMIDE. (Reaction C.) Add 15 g. of the above thoroughly drained sulphonamide to 10 ml. of concentrated hydrochloric acid diluted with 20 ml. water, and boil the mixture gently under reflux for i hour. Then add 30 ml. of water and heat the mixture again to boiling, with the addition of a small quantity of animal charcoal. Filter the boiling solution, and add powdered sodium carbonate in small quantities to the filtrate with stirring until all eflFervescence ceases and the sulphanilamide is precipitated as a white powder. Cool the mixture thoroughly and filter oflF the sulphanilamide at the pump, wash with water and dry. Yield, ca. 10 g. 

In preparing an aqueous sol ution of a diazonium salt, such as benzene-diazonium chloride, it is usual to dissolve the amine in a slight excess (about 2 2 molecular equivalents) of dilute hydrochloric acid (or alternatively to dissolve the crystalline amine hydrochloride in i 2 equivalents of the acid) and then add an aqueous solution of a metallic nitrite. Nitrous acid is thus generated in situ, and reacts with the amine salt to give the diazonium compound. For a successful preparation of an aqueous solution of the diazonium salt, however, two conditions must always be observed ... 

To prepare the hydrochloride, add about i g. of aminoazobenzene to 200 ml. of dilute hydrochloric acid and boil until nearly all the solid material has dissolved. Filter hot and allow to cool slowly. Aminoazobenzene hydrochloride separates as beautiful steel-blue crystals filter and dry. If a small quantity of the powdered hydrochloride is moistened with water and a few drops of ammonia added, the blue hydrochloride is converted back to the yellowish-brown base. 

Prepare a mixture of 30 ml, of aniline, 8 g. of o-chloro-benzoic acid, 8 g. of anhydrous potassium carbonate and 0 4 g. of copper oxide in a 500 ml. round-bottomed flask fitted with an air-condenser, and then boil the mixture under reflux for 1 5 hours the mixture tends to foam during the earlier part of the heating owing to the evolution of carbon dioxide, and hence the large flask is used. When the heating has been completed, fit the flask with a steam-distillation head, and stcam-distil the crude product until all the excess of aniline has been removed. The residual solution now contains the potassium. V-phenylanthrani-late add ca. 2 g. of animal charcoal to this solution, boil for about 5 minutes, and filter hot. Add dilute hydrochloric acid (1 1 by volume) to the filtrate until no further precipitation occurs, and then cool in ice-water with stirring. Filter otT the. V-phcnylanthranilic acid at the pump, wash with water, drain and dry. Yield, 9-9 5 g. I he acid may be recrystallised from aqueous ethanol, or methylated spirit, with addition of charcoal if necessary, and is obtained as colourless crystals, m.p. 185-186°. 

To prepare a sample of the hydrochloride, add 0-5 ml. of the base to 10 ml, of dilute hydrochloric acid in an evaporating basin and evaporate to dryness, preferably in a vacuum desiccator. Recrystallise the dry residue from petroleum (b.p. 60-80°). The hydrochloride separates as white crystals, m.p. 90°. 

Ketonic Hydrolysis. Hot dilute caustic alkalis or hydrochloric acid first hydrolyse off the ethyl group, and then remove carbon dioxide, a mono- or di-substituted acetone being thus obtained ... 

Whilst the solution is still hot, add dilute hydrochloric acid until the stirred solution is just acid to litmus, and then distil off as much ethanol as possible, using the water-bath. Now add more dilute hydrochloric acid to the residual hot solution until it is just acid to methyl-orange. The 5,5-dimethyl-cyclohexan-1,3-dione separates as an oil which solidifies on cooling. Filter the product at the pump, wash it with ice-cold water, and dry it in a desiccator. Yield of the pale cream-coloured crystals, 12 g. m.p. 136-145 (preliminary softening). 

Many aldehydes and ketones can be reduced directly by Clenimemen s method, in which the aldehyde or ketone is boiled with dilute hydrochloric acid and amalgamated zinc. />-Methylacetophenone (or methyl />-tolyl ketone) is reduced under these conditions to />-ethyltoluene. An excess of the reducing agent is employed in order to pre ent the formation of unsaturated hydrocarbons. 

During this period hydrogen chloride continues to be liberally evolved, and the product darkens considerably in colour. Now pour the product cautiously into 500 ml. of dilute hydrochloric acid and 100 g. of chipped ice in a separating-funnel, and shake the mixture thoroughly this operation removes the dark colour, and the toluene solution becomes yellow. Run off the lower acid layer, and extract the toluene three times with water. Finally dry the toluene solution over calcium chloride. 

Gently warm a mixture of 32 g. (32 ml.) of ethyl acetoacetate and 10 g. of aldehyde-ammonia in a 400 ml. beaker by direct heating on a gauze, stirring the mixture carefully with a thermometer. As soon as the reaction starts, remove the heating, and replace it when the reaction slackens, but do not allow the temperature of the mixture to exceed 100-no the reaction is rapidly completed. Add to the mixture about twice its volume of 2A -hydrochloric acid, and stir the mass until the deposit either becomes solid or forms a thick paste, according to the quality of the aldehyde-ammonia employed. Decant the aqueous acid layer, repeat the extraction of the deposit with more acid, and again decant the acid, or filter off the deposit if it is solid. Transfer the deposit to a conical flask and recrystallise it twice from ethanol (or methylated spirit) diluted with an equal volume of water. The i,4-dihydro-collidine-3,5-dicarboxylic diethyl ester (I) is obtained as colourless crystals, m.p. 130-131°. Yield 12 5 g,... 

The mixed bases are dissolved in dilute hydrochloric acid and sodium nitrite solution added. The aniline is thus diazotised and, if the mixture is subsequently boiled, converted into phenol. The solution is then made alkaline and steam-distilled, the quinoline passing over, while the phenol remains behind in the alkaline solution. 

Dissolve 13 g. of sodium in 30 ml. of absolute ethanol in a 250 ml. flask carrying a reflux condenser, then add 10 g. (9 5 ml.) of redistilled ethyl malonate, and place the flask on a boiling water-bath. Without delay, add a solution of 5 3 g. of thiourea in a minimum of boiling absolute ethanol (about 100 ml.). The sodium salt of thiobarbituric acid rapidly begins to separate. Fit the water-condenser with a calcium chloride guard-tube (Fig. 61, p. 105), and boil the mixture on the water-bath for 1 hour. Cool the mixture, filter off the sodium salt at the pump and wash it with a small quantity of cold acetone. Dissolve the salt in warm water and liberate the acid by the addition of 30 ml. of concentrated hydrochloric acid diluted with 30 ml. of water. Cool the mixture, filter off the thiobarbituric acid, and recrystallise it from hot water. Colourless crystals, m.p. 245 with decomposition (immersed at 230°). Yield, 3 5 -4 0 g. 

Cool the reaction-solution, and pour it into a 250 ml. beaker, washing out the flask with ca. 50 ml. of water into the beaker. Chill the solution in ice-water and add dilute hydrochloric acid with stirring until the solution is just acid when spotted externally on to Congo Red paper. The arsinic acid rapidly separates. Filter at the pump, wash well with water and drain. (Yield of crude dry product, 7-5-8 o g. m.p. 200-203°.)... 

Sulphur. Moisten the centre of a filter-paper with lead acetate solution. Then add about 10 ml. of dilute hydrochloric acid to the residue in the evaporating-basin, and at once cover the latter with the paper. If zinc sulphide is present in the residue, the hydrogen sulphide evolved will give a definite daA brown coloration with the lead acetate paper. The presence of hydrogen sulphide can often be confirmed by its odour. 

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