EN 14712:2005 – Surface active agents – Determination of physical stability in alkaline and acid solutions

1 Scope
This European Standard specifies a method for the determination of physical stability of surface active agents in alkaline and acid solutions. It is applicable to all classes of surface active agents and also to other substances or mixtures such as polymers, complexing agents and formulations of surface active agents.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN ISO 3696, Water for analytical laboratory use — Specification and test methods (ISO 3696:1987).
3 Terms and definitions For the purposes of this European Standard, the following terms and definitions apply.
3.1 alkaline stability maximum mass concentration of sodium hydroxide (purity at least of 98 %) in grams per litre at which the surface active agent can be dissolved in the alkaline solution with a mass concentration of 1 % to yield a stable solution 3.2 acid stability maximum volume concentration of sulfuric acid (purity 95 % to 98 %), in millilitres per litre, at which the surface active agent can be dissolved in the acid solution with a mass concentration of 1 % to yield a stable solution
3.3 other bases and acids other bases and acids may be used. This should be described together with the purity in the test report
4 Principle
Aqueous solutions are prepared with increasing concentrations of sodium hydroxide or sulfuric acid respectively. Then the surface active agent to be tested is mixed in these aqueous solutions.
The formulations are examined visually after 24 h of storage at ambient temperature (22 ± 3) °C to see whether a stable solution resulted or not. Clear homogeneous solutions are always considered stable, whereas phase separation indicates instability. Homogeneous opalescent or homogeneous turbid samples can be considered either stable or unstable depending on the surface active agent application.
5 Reagents
5.1 Water, grade 3, in accordance with EN ISO 3696.
5.2 Sodium hydroxide, NaOH, analytical grade, preferably as an aqueous solution with a mass concentration of 30 % NaOH (this corresponds to 398 g NaOH (100 % active substance) in 1 l ; density ρ = 1,328 g/ml at 20 °C). 5.3 Sulfuric acid, H 2 SO 4 , analytical grade, preferably as an aqueous solution with a mass concentration of 25 % H 2 SO 4 (density ρ = 1,18 g/ml at 20 °C).
EN 14712:2005 – Surface active agents – Determination of physical stability in alkaline and acid solutions