BS EN 901:2013 pdf download – Chemicals used for treatment of water intended for human consumption — Sodium hypochlorite
3.1.6 CAS Registry Number
3.1.7 EINECS reference
3.2 Commercial form
The product is supplied as an aqueous solution with an available (active) chlorine concentration up to a mass fraction of 18 %.
3.3 Physical properties
3.3.1 Appearance and odour
The product is a clear yellowish-green solution with a faint chlorinous odour.
3.3.2 Density
The density of the product varies between 1,13 g/ml and 1,30 g/ml at 20 °C.
3.3.3 Solubility in water
The product is capable of being mixed with water in any proportion.
3.3.4 Vapour pressure
Approximately 2,5 kPa at 20 °C.
3.3.5 Boiling point at 100 kPa
Not applicable.
3.3.6 Crystallisation and freezing point
At about – 10 °C crystallisation of NaOCl . 6 H 2 O starts.
Freezing of the concentrated product takes place between – 20 °C and – 30 °C.
3.3.7 Specific heat
The specific heat is 3,48 kJ/(kg.K) for a solution with an available active chlorine concentration of mass fraction between 14 % and 15 %.
3.3.8 Viscosity (dynamic)
2,6 mPa.s at 20 °C.
3.3.9 Critical temperature
Not applicable.
3.3.10 Critical pressure
Not applicable.
3.3.11 Physical hardness
Not applicable.
3.4 Chemical properties
The product is an alkaline solution with a pH value greater than 11 at 20 °C.
It reacts with acids and acidic salts to form chlorine.
Vigorous reactions occur with reducing chemicals. It is a strong oxidant (E° Red for (ClO – ) = 0,89 V).
4 Purity criteria
4.1 General
This European Standard specifies the minimum purity requirements for sodium hypochlorite used for treating water intended for human consumption. Limits are given for impurities commonly present in the product. Depending on the raw material and the manufacturing process, other impurities may be present and, if so, the user, and when necessary the relevant authorities, shall be notified. Users of the product should check the national regulations to clarify whether it is of appropriate purity for treating water intended for human consumption, taking into account raw water quality, required dosage, contents of other impurities and additives used in the product that are not stated in this product standard. Limits have been given for impurities and chemical parameters where these are likely to be present in significant quantities from the current production process and raw materials.
If the production process or the raw materials bring about the presence of significant amounts of impurities, by-products or additives, the user shall be notified.
4.2 Composition of commercial product Sodium hypochlorite is available only in solutions with concentrations up to 18 % active chlorine at the time of delivery by the producer. Common concentrated products contain a minimum of 12 % active chlorine. Diluted solutions are also available. The concentration of sodium hypochlorite shall be equal to or greater than the value specified by the manufacturer.
4.3 Impurities and main by-products The product contains sodium chloride (NaCl) in equimolar amounts at minimum, and a small portion of sodium hydroxide (NaOH) which keeps the product alkaline. Thus a little amount of sodium carbonate (Na 2 CO 3 ) can be present, too.
The sodium chlorate (NaClO 3 ) content shall not exceed a mass fraction of 5,4 % of available chlorine at the time of delivery by the producer. The product shall be visibly free from deposits or suspended matter.
NOTE Sodium chlorate is a by-product of the manufacturing process and can be formed during storage (see 6.5.1).
4.4 Chemical parameters
The product shall conform to the requirements specified in Table 1.
5 Test methods
5.1 Sampling
Observe the general recommendations of ISO 3165 and take account of ISO 6206.
5.2 Analysis
5.2.1 Determination of available chlorine content (main product) General
This method applies to all commercial products with available chlorine contents within the range of 70 g/l
to 170 g/l.
NOTE It detects all oxidising agents being active in weak acidic solutions, i.e. hypochlorite/chlorine, iodate, and partially chloramines, Fe(III), etc. Bromate and chlorate are not covered under these conditions. Principle
Sodium hypochlorite reacts with potassium iodide to release iodine in the presence of acetic acid. The iodine is titrated with sodium thiosulfate standard volumetric solution in the presence of starch indicator solution.