Sulphuric acid and oleums for industrial use — Determination of sulphur dioxide content — Iodometric...
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…
Sulphur for industrial use — Determination of ash at 850-900 degrees C and of residue at 200 degrees...
Application to products containing at least 98 % of elemental sulphur, expressed as a percentage by mass, of the product dried at 80 °C for 2 h. The difference between the ash and the residue corresponds to the "non-volatile bituminous matter" content at 200 °C. The principle of ashing consists in slow combustion in air of a test portion of the dried product. Heating in a furnace,…
Potassium hydroxide for industrial use — Determination of silica content — Reduced molybdosilicate p...
The method is applicable to products having silica contents exceeding 10 mg/kg. The principle is based on the formation of yellow oxidized silico-molybdic complex in a strongly acid medium, in the presence of boric acid to suppress interference by fluorides. Selective reduction of this complex with a mixture of aminonaphtholsulphonic acid (4-amino-3-hydroxynaphthalene-1-sulphonic acid), sodium…
Sodium tripolyphosphate and sodium pyrophosphate for industrial use — Determination of total phospho...
Based on hydrolysis of a test portion by prolonged boiling in the presence of hydrochloric acid. Precipitation of the phosphate ions in the form of quinoline phosphomolybdate in the presence of acetone. Filtration by means of a filter crucible, washing, drying and weighing of the precipitate.
Phosphoric acid for industrial use — Determination of arsenic content — Silver diethyldithiocarbamat...
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…
Sodium hydroxide for industrial use — Determination of sulphur compounds — Method by reduction and t...
Applicable to products the content of which, expressed as sulphate, is equal or more than 5 mg/kg. The principle consists in the reduction of the sulphur compounds to hydrogen sulphide by heating with a mixture of hydriodic acid and hypophosphorous acid. Distillation of the hydrogen sulphide by a current of oxygen-free nitrogen in a mixture of sodium hydroxide and acetone. Titration of the…
