Sodium pyrophosphate for industrial use — Estimation of pyrophosphate content — Potentiometric metho...
Applicable to products containing at least 90 % (m/m) of tetrasodium pyrophosphate and in the absence of more condensed forms of phosphates. The reaction based on conversion of tetrasodium pyrophosphate to disodium dihydrogenpyrophosphate by addition of hydrochloric acid. Introduction of zinc sulfate in solution for precipitation of zinc pyrophosphate and formation of sulphuric acid.…
Sodium tripolyphosphate for industrial use — Estimation of tripolyphophate content — Tris(ethylenedi...
Not applicable in the presence of metaphosphate. The presence of pyrophosphate at normal concentrations Ämaximum 6 % (m/m)Ü does not interfere. The principle consists in precipitation of tripolyphosphate as its complex with tris(ethylenediamine) cobalt(III) chloride at a pH of between 3 and 4 in a buffered medium. Filtration, washing, drying and weighing of the precipitate. Details the…
Sodium hydroxide for industrial use — Method of assay
Method for determination of the titre; this is expressed conventionally as percentages by mass of NaOH, a) as total alkalinity and b) as caustic alkalinity, corresponding to the total alkalinity less the alkalinity due to carbonates. The principle consists in titration of the total alkalinity with standard volumetric hydrochloric acid solution in the presence of methyl orange as indicator.…
Sodium hydroxide for industrial use — Determination of iron content — 1,10- Phenanthroline photometr...
Specifies a method that is more sensitive and more widely used than the 2,2'-bipyridyl method. It is applicable to products having iron contents equal to or greater than 0.5 mg/kg. The principle is based on the reduction of trivalent iron by hydroxylammonium chloride, formation of a bivalent iron/1,10-phenanthroline complex in a buffered system. Photometric measurement of the coloured…
Sodium hydroxide for industrial use — Determination of silica content — Reduced silico-molybdic comp...
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…
Phosphoric acid for industrial use — Determination of sulphate content — Method by reduction and tit...
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…
Sulphur for industrial use — Determination of total carbon content — Titrimetric method
Gives the potentiometric and visual methods als alternatives for the final titration. The principle consists in the combustion of the sulphur in a current of oxygen. Oxidation and fixation of the sulphur dioxide and trioxide gases in chromic and sulphuric acid solutions. Absorption of the carbon dioxide formed in a solution of barium hydroxide, followed by titration in the presence of…
