1 Scope
This standard specifies five methods for the measurement of the cloud point of non-ionic surface active agents.
Methods A, B and C are applicable to non-ionic surface active agents derived from ethylene oxide by condensation with a lipophilic compound which has no oxypropylene groups. The selection of the method (A, B or C) depends on the temperature at which the aqueous solution of the product being tested becomes cloudy.
Methods D and E are intended for use, after agreement between the parties concerned, with products for which methods A, B and C prove unsatisfactory. Such products include mixed non-ionic surface active agents such as those derived from ethylene oxide/propylene oxide block copolymers. The selection of the method (D or E) depends on the temperature at which the acid aqueous solution of the product being tested becomes cloudy. Method E is not applicable, however, to products derived from fatty acids or fatty-acid esters.
Note: The cloud point of products derived from fatty acids or fatty-acid esters can only be determined if the repeatability of the determination is verified.
2 Normative reference
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 (including any amendments) applies.
GB/T 6367 Surface active agents — Preparation of water with known calcium hardness (GB/T 6367-997, idt ISO 2174:1990)
GB/T 6372-2006 Surface active agents and detergents — Methods of sample division (ISO 607:1980, IDT)
ISO 1773:1976 Laboratory glassware - Boiling flasks (narrow-necked)
3 Selection of method
Note: It may be impossible to measure the cloud temperature of certain very pure derivatives of ethylene oxide if dissolved in distilled water of very low conductivity. In such cases, the solution does not become heterogeneous at a definite temperature; instead, only a slight loss of clarity is observed. However, replacement of the distilled water by an aqueous solution of sodium chloride (234 mg/L) enables the cloud temperature to be measured.
3.1 Method A
If the aqueous solution of the sample becomes cloudy at a temperature between 10°C and 90°C, carry out the measurement in distilled water (see 8.1).
3.2 Method B
If the aqueous solution of the sample becomes cloudy at a temperature lower than 10°C, or if the sample is not sufficiently soluble in water, carry out the measurement in an aqueous 25% (m/m) solution of n-butyldiglycol (see 8.2). However, this method is not applicable to certain samples with low ethylene oxide contents and which are insoluble in the aqueous 25 % (m/m) solution of n-butyldiglycol.
3.3 Method C
If the aqueous solution of the sample becomes cloudy at a temperature higher than 90°C, carry out the measurement in a sealed ampoule, which makes it possible, by operating under pressure, to reach temperatures higher than the boiling point of the solution at atmospheric pressure (see 8.3).
Note: It is also possible, if agreed between the parties concerned, to determine the cloud point in salt solution, but this technique is not so sensitive and there is no simple correlation between the results obtained in salt solution and those obtained with the sealed-ampoule method.
Foreword i
1 Scope
2 Normative reference
3 Selection of method
4 Principle
5 Reagents and solutions
6 Apparatuses and equipment
7 Sampling
8 Determination procedures
9 Expression of analysis results
10 Precision
11 Test report
