71.060.30 - Acids

Complements the second edition of ISO 3139/1976.

Contains guides concerning the procedure to be followed and the precautions to be observed for the taking, preparation and storage of samples with the view of assess their quality. Deals with the means of delivery, containers for taking samples, technical means for mixing and heating systems. Details the sampling of thermal-process and wet-process acids from large containers and mobile tanks and the safety measures. Has also been approved by the IUPAC.

Two cases are considered: sulphuric acid contents equal to or lower than 98 % (m/m) and sulphuric acid contents higher than 98 % (m/m). The principle is based on oxidation of a test portion with hydrogen peroxide and titration of the total acidity with a standard volumetric sodium hydroxide solution, in the presence of methyl red as indicator. - Replaces ISO Recommendation R 910-1968.

Applicable to products whether or not they are homogeneous and whether or not they contain polyphosphoric acids. Specifies preliminary hydrolysis of the polyphosphoric acids by boiling in the presence of hydrochloric acid. The precipitation of the phosphoric acid is carried out in the form of quinoline phosphomolybdate in the presence of acetone. Filtration by a filter crucible, washing, drying and weighing of the precipitate.

The principle consists in titration of a test portion with a standard volumetric solution of sodium hydroxide in presence of bromcresol green as indicator. Replaces ISO Recommendation R 904-1968.

Applicable to products the F content of which is equal to or more than 0.5 mg/kg. Specifies the separation of the element from a test portion by steam distillation in a phosphoric acid medium. Formation of a blue-coloured complex with a combined reagent alizarin complexone/lanthanum nitrate in a buffered medium at the pH of 4.6. Addition of acetone to increase the stability of the complex and the sensitivity. Photometric measurement of the complex at a wavelength of about 600 nm.

Applicable to products having a water content between 0.01 % (m/m) and 0.5 % (m/m). Is supplemented by ISO 3700 and intended for reference purposes. Bases on addition of a cooled test portion to cooled dry pyridine containing 5 % of anhydous hydrogen fluoride. The apparatus for measuring the test portion and titration and the measuring vessel are shon in figures. Subsequent electrometric titration of the water with the Karl Fischer reagent.

Contains also titrimetric methods for determination of the total acidity, the hexafluorosilicic acid content and the non-volatile acids content and a method for calculating the hydrogen fluoric content. Specifies the scope and the field of application of these methods and declares the principle of the procedures. This second edition results from the incorporation of Addendum in the first one. Cancels and replaces the first edition ISO 3139/1974.

Applicable of products the SO2 content of which is equal to or more than 2 mg/kg. Based on the displacement of the sulphur dioxide present in the test portion by a current of pure nitrogen and absorption in a known volume of iodine solution. Titration of the excess of iodine with standard volumetric sodium thiosulphate solution. The diagram of the glass apparatus for absorption is shown in a figure.

This part contains a method for taking laboratory samples intended for the determination of the water content and the preparations of the test samples. Contains instructions for handling with the material. Applicable for taking samples of this highly corrosive liquid from road and rail tanks, drums and cylinders. The principle consists in allowing the liquid of one of these containers to flow in a cooled evacuated stainless steel cylinder or cylinders of not less than 1 kg total capacity. The apparatus for sampling is shown in a figure. Part Two deals with the preparation of the test sample by introduction of the liquid into a polyolefin cylinder containing two layers of ice. Has also been approved by the IUPAC.

Applicable to products having sulphate contents equal to or more than 0.0005 % (m/m). Analysis by reduction of the sulphate to sulphide by a mixture of hydriodic acid and hypophosphorus acid. Absorption of the hydrogen sulphide evolved in a mixture of acetone and sodium hydroxide solution. Titration with a standard volumetric solution of mercury(II) acetate in the presence of dithizone as indicator. Has also been approved by the IUPAC.

The turbidimetric method is applicable to products containing less than 0.1 % (m/m) of soluble sulphates. The principle consists in evaporation of a test portion to dryness and solution of the residue in hydrochloric acid. Measurement of the turbidity obtained by precipitation, under well defined conditions, of barium sulphate. Has also been approved by the IUPAC.

The sulphate present in a test portion is reduced to sulphide by a mixture of hydriodic and phosphinic (hypophosphorous) acids. The hydrogen sulphide evolved is absorbed in an excess of cadmium acetate solution. The cadmium sulphide formed is oxidized by an excess of standard volumetric potassium iodate/iodide solsution, and the excess iodine is titrated with standard volumetric sodium thiosulphate solution, using starch as indicator. The method is applicable to products having sulphate contents between 0.2 and 6 % (m/m).

The hydrogen sulphide in a test portion is removed in a stream of nitrogen and absorbed in a solution of sodiumhydroxide in aqueous acetone. the sulphide ions are titrated with standard volumetric mercury(II) acetate solution, in the presence of 1,5-diphenylthiocarbazone (dithizone) as indicator. The method is applicable to products having hydrogen sulfide contents greater than or equal to 0.05 mg/kg.

A yellow complex is formed by reaction of the vanadium present in a test portion with phosphoric acid and sodium tungstate in acid medium. The spectrometric measurement of the absorbance is carried out at a wavelength of about 425 nm. The method is applicable to products having a vanadium content equal to or greater than 3 mg/kg.

Covers a method consisting in separating the fluorine from a test portion by distillation in the presence of perchloric acid, followed by potentiometric titration of the distillate with lanthanum nitrate solution using a fluoride ion-selective electrode. Is applicable to products having total available fluorine contents in the range between 15 and 35 % (m/m).

The general method is applicable to phosphoric acid not containing polyphosphoric acids and to products having a calcium content equal to or greater than 0.020 % (m/m). In special cases a preliminary hydrolysis of polyphosphoric acids is carried out by prolonged boiling in the presence of hydrochloric acid. Precipitation of calcium as calcium oxalate at pH 4 0.3, filtration of the precipitate, dissolution in hydrochloric acid and re-precipitation under the same operating conditions in order to purify the precipitate. Oxidimetric titration in sulphuric acid solution by means of potassium permanganate. - Cancels and replaces ISO Recommendation R 848-1968.

The lead is extracted from a diluted test portion into a solution of diethylammonium diethyldithiocarbamate in xylene. The xylene extract is separated and aspirated into the acetylene/air flame of an atomic absorption spectrometer. The spectrometric measurements are carried out at a wavelength of about 217 nm or, alternatively, about 283 nm. The method is applicable to phosphoric acids having lead contents greater than 0.1 mg/kg.

Suitable for use as a routine alternative to the Karl Fischer method specified in ISO 3699 but may give a lower standard of accuracy. Applicable to products having a water content between 0.01 % (m/m) and 0.4 % (m/m). Bases on the measurement of the conductance of anhydrous products using a dip cell electrode. Determination of the corresponding content by means of a calibration graph making a correction for the non-volatile acid content. Has also been approved by the IUPAC.

The method is applicable to products having oxidizing or reducing matter contents equal to or greater than 0.001 % (m/m). The principle is based on detection of the presence of these matter by a preliminary qualitative test. In the case of oxidizing matter adding of potassium iodide solution and titration of the liberated iodine with sodium thiosulphate standard volumetric solution until the blue colour disappears. In the case of reducing matter transferring of the test portion to an exactly measured volume of iodine solution and titration of the excess of iodine with the sodium thiosulphate standard volumetric solution. - Cancels and replaces ISO Recommendation R 908-1968.

Describes a method applicable to products having aresenic contents equal to or greater than 0,1 mg/kg. As far as principle, the reagents and apparatus to be used are concerned, reference is made to ISO 2590, with some modifications added. For example, the reduction of arsenic by zinc is carried out in sulphuric acid medium. Provides information on the expression of results and the particulars to be included in the test report. The annex lists ISO publications covering the same subject.

Describes a method applicable to products having arsenic contents equal to or greater than 0,2 mg/kg. As far as principle, reagents and apparatus to be used are concerned, reference is amde to ISO 2590. Provides information on the expression of results and the particular to be included in the test report. The annex lists ISO publications covering the same subject.

Applicable to products having chloride contents equal or more than 0,0002 % (m/m). Potentiometric titration of the ions with silver nitrate solution in a nitric acid acetone-water medium using a silver measurement electrode and a calomel reference electrode.

Based on evaporation of a test portion in a platinum dish, followed by ignition in an electric furnace, controlled at (850 50) °C, and weighing. - Replaces ISO Recommendation R 913-1968.

The method is applicable to products having a total nitrogen content equal to or greater than 0.05 % (m/m). The principle consists in the conversion of the nitrogen present in a test portion to ammonia by means of nascent hydrogen. Distillation and absorption of the ammonia in an excess of standard volumetric sulphuric acid solution, and back-titration with a standard volumetric sodium hydroxide solution in the presence of an indicator. - Replaces ISO Recommendation R 914-1968.

Two cases are considered: content of nitrous compounds, expressed as HNO2, equal to or greater than 0,01 % (m/m) and content of nitrous compounds, expressed as HNO2, less than 0,01 % (m/m). The principle consists in oxidatiuon of the compounds present in a test portion by an excess of standard volumetric potassium permanganate solution. Addition of an excess of a standard volumetric iron(II) sulphate solution, and titration of this excess with a standard volumetric potassium permanganate solution. Replaces ISO Recommendation R 1981-1971.

The principle of the method consists inevaporation of a test portion in a platinum dish, conversion of the residue to sulphates by treatment with sulphuric acid; ignition in an electric furnace, controlled at (800 +- 25) °C, and weighing. Replaces ISO Recommendation R 1983-1971.

The principle consists in the determination of density at 20 °C by means of a hydrometer. Evaluation of the corresponding sulphuric acid concentration by means of the table. - Replaces ISO Recommendation R 911-1968.

Applicable to products having a Ca content of more than 50 mg/kg. Soluble SiO2 present in the solution at levels lower than 5 g/ml does not interfere. The principle consists in addition, to a hydrochloric acid solution of the test portion, of sodium ions to promote and stabilize the emission of calcium and of lanthanum ions to suppress the interference of aluminium. Specifies the aspiration of the solution into an acetylene-dinitrogen monoxide flame. Photometric measurement of the absorption of the 422.7-nm line emitted by a hollow- cathode calcium lamp. Has also been approved by the IUPAC.

The method is applicable to products having sulphate contents equal to or greater than 0,1 % (m/m). The principle consists in precipitation of the sulphates contained in a test portion as barium sulphate in diluted hydrochloric acid medium. Separation of the precipitate obtained and ignition of the residue in an electric furnace, amintained at (800 +- 25 ) °C, and weighing. Replaces ISO Recommendation R 906-1968.

The principle of the method consists in evaporation of a test portion; conversion of the salts in sulphates by treatment with sulphuric acid. Ignition in an electric furnace, maintained at (800 +- 50) °C, and weighing. Replaces ISO Recommendation R 907-1968.

Specifies the determination of density at 20 °C by means of a hydrometer. Evaluation of the corresponding concentration by means of a table. Replaces ISO Recommendation R 905-1968.

Applicable to products having Cl- contents, expressed as chlorine, equal to or more than 0.001 % (m/m). The lower limit can be extended downwards by using weaker standard reference and volumetric solutions. Describes potentiometric titration of the ions with silver nitrate solution in a nitric acid-acetone-water medium using a silver measurement electrode and a calomel reference electrode.

Applicable to products having a content, expressed as N, equal to or more than 0.2 mg/kg. Consists in oxidation of nitrous nitrogen to nitric nitrogen by potassium permanganate and reaction of nitrogen(V) with 3,4-xylenol under specified conditions to form a nitrate derivative. Subsequent destillation of the nitrate derivative and absorption in sodium hydroxide solution. Spectrophotometric measurement of the yellow nitrophenol at a wavelength of about 435 nm.

Amendment to sulphuric acid for industrial use. Relates to potentiometric titration for the determination of clorides content.

Applicable to products having SO2 contents between 0.002 % (m/m) and 0.20 % (m/m). The principle consists in addition of a measured volume of iodine solution to a test portion. Back-titration of the excess iodine using a standard volumetric sodium thiosulphate solution and calculation of the SO2 content from the amount of iodine used.

Applicable to products having H2 SiF6 contents between 0.01 % (m/m) and 0.2 % (m/m). Gives introductory instructions to the risk in handling with the product. The principle of analysis consists in formation of oxidized molybdosilicate (yellow) in weakly acid medium in the presence of boric acid to suppress interference by fluorine. Selective reduction of this complex after addition of sulphuric acid solution and oxalic acid to eliminate interference from phosphates. Photometric measurement of the blue coloured complex at a wavelength of about 795 nm.

Applicable to products having As contents of more than 0.1 mg/kg. Relates to the method of analysis according to ISO 2590. Reduction of the As by zinc in a hydrochloric acid solution with the formation of arsine. Absorption of the arsine in a solution of silver diethyldithiocarbamate in pyridine. Photometric measurement of the purplish-red colour produced by the colloidally dispersed silver at the maximum of the absorption curve at a wavelength of about 540 nm. Determination of the quantity of As by means of the calibration curve.

Specifies a reduced molybdosilicate spectrophotometric method for the determination of the soluble silica content of phosphoric acid for industrial use. The method can be used for the determination of 1 µg of soluble silica in the presence of 20 mg of phosphorus pentoxide. It is thus, for example, applicable to the determination of soluble silica contents greater than 30 mg/kg if the phosphoric acid contains 60 % of phosphorus pentoxide.

Applicable to products the SO4 content of which is equal to or more than 0.0001 % (m/m). Heating of a test portion to dryness in the presence of sodium carbonate. Reduction of the sulphureous residue to sulphides by a mixture of hydriodic acid and hypophosphorus acid. Absorption of the hydrogen sulphide evolved in a mixture of sodium hydroxide solution and acetone. Titration with standard volumetric mercury(II) acetate solution in the presence of dithizone as indicator. A typical apparatus for reduction and distillation is shown in a figure.

Applicable to contents of between 0.005 % (m/m) and 0.3 % (m/m) expressed in sulphuric acid. Preparation of the samples according to ISO 3137. Removal of volatile acids by evaporation and titration of the remaining acidity with standard volumetric sodium hydroxide solution in the presence of phenolphthalein as indicator. The evaporation is carried out on a boiling water bath in a fume cupboard.

Applicable to products containing more than 0.0001 % (m/m) of ammoniacal nitrogen. The procedure described is siutable for contents between 0.0001 % (m/m) and 0.0005 % (m/m). The principle of the analysis consists in distillation, with entrainment by steam, of the ammonia in the presence of an excess of sodium hydroxide and collection of the distillate in an excess of acid solution. Neutralization of the excess of acid and formation of the coloured complex by treatment with sodium phenate and sodium hypochlorite in the presence of acetone. Spectrophotometric measurement of the indophenol obtained at a wavelength of about 630 nm. Has also been approved by the IUPAC.

Applicable to products having contents of more than 0.0001 % (m/m). The procedure described is suitable for contents between 0.0001 % (m/m) and 0.0005 % (m/m). It bases on distillation, with entrainment by steam, of the ammonia in the presence of an excess of sodium hydroxide and collection of the distillate in an excess of acid solution. Neutralization of the dexcess of acid and formation of the coloured complex by treatment with sodium phenate and sodium hypochlorite in the presence of acetone. Spectrophotometric measurement of the indophenol obtained at a wavelength of about 630 nm. Has also been approved by the IUPAC.

Describes the determination of density at 20 °C by means of a hydrometer. The correspondence between density and concentration of aqueous solutions is given in a table. Has also been approved by the IUPAC.

Applicable to products having chloride contents equal or more than 0.0003 % (m/m) expressed in hydrochloric acid. Specifies the potentiometric titration of the chloride ions with silver nitrate solution in a sulphuric acid medium using a silver measurement electrode and a calomel reference electrode.

Applicable to the determination of contents exceeding 1 mg/kg. The principle bases on evaporation of the test portion, dissolution in hydrochloric acid and reduction by hydroxylammonium chloride. Formation of complexes of interferring elements with ammonium citrate and potassium cyanide. Extraction of the lead at a pH of between 8.5 and 10 by a solution of dithizone in chloroform. Elimination of excess dithizone by an ammoniacal solution of potassium cyanide. Photometric measurement in chloroform solution at a wavelength of about 520 nm. Has also been approved by the IUPAC.

The method ia applicable of oxide of nitrogen contents equal to or greater than 0,00002 % (m/m). The principle is based on oxidation of nitrous nitrogen to nitric nitrogen by potassium permanganate. Reaction of nitric nitrogen with 2,4-xylenol under specified conditions to form a nitrate derivate. Distillation of the nitrate derivate and absorption in sodium hydroxide solution. Spectrophotometric measurement of the yellow coloured nitrophenol at a wavelength of about 445 nm.

The method is based on titration of a dissolved test portion with a standard volumetric solution of sodium hydroxide in the presence of mannitol or sorbitol, using phenolphthalein as indicator. Water free from carbon dioxide, shall be used in the test .

The method is applicable to the determination of iron contents greater than 0,0001 % (m/m). The principle consists in evaporation of a test portion, taking up by means of hydrochloric acid and reduction of iron(III) by means of hydroxylammonium chloride. Formation of iron(II)-2,2' -dipyridyl complex in ammonium acetate medium. Photometric measurement of the coloured complex at a wavelength of about 522 nm.