3.1 The cloud point temperature is a reproducible characteristic of certain pure nonionic surfactants. It is also characteristic of certain nonionic surfactant formulated systems. This test method is appropriate for both systems.

Note 1: If the transition from a distinctly cloudy to a clear solution is not sharp, that is, if it does not take place within a range of 1 °C, this test method is not appropriate.

1.1 This test method covers a procedure to determine the “cloud point” of nonionic surfactants or detergent systems. Cloud Point is the temperature at which dissolved components (solids or liquids) are no longer completely soluble, precipating as a second phase giving the fluid a cloudy appearance. It is limited to those surfactants and detergent systems for which the visible solubility change occurs over a range of 1 °C or less at concentrations of 0.5 % to 1.0 % in DI water between 30 °C and 95 °C.

1.2 Chemical Limitations—Nonionic surfactants that exhibit a characteristic cloud point in general terms consist of a water-in-soluble moiety condensed with 50 % to 75 % by weight of ethylene oxide. If the level of ethoxylation is too low the surfactant may not be water soluble at temperatures less than 30 °C, and if it is too high no cloud point may exist.

1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.