Tests for Class 5 (Oxidizing Materials)

Class 5.1: Is the substance or article an Oxidizing Solid or Liquid?

Tests for Oxidizing Solids & Liquids

The test for oxidizing solids is designed to measure the potential for a solid substance to increase the burning rate or burning intensity of a combustible substance when the two are thoroughly mixed. Tests are conducted on the substance to be evaluated mixed with dry fibrous cellulose in mixing ratios of 1:1 and 4:1, by mass, of sample to cellulose. The burning characteristics of the mixtures are compared with the standard 3:7 mixture, by mass, of potassium bromate to cellulose. If the burning time is equal to or less than this standard mixture, the burning times are compared with those from the Packing Group I or II reference standards, 3:2 and 2:3 ratios, by mass, of potassium bromate to cellulose respectively.

The test for oxidizing liquids measures the potential for a liquid substance to 1) increase the burning rate of a combustible substance when the two are thoroughly mixed or 2) to form a mixture that spontaneously ignites. The liquid is mixed with fibrous cellulose in a 1:1 ratio, by mass. The mixture is then heated in a pressure vessel and the rate of pressure rise is measured with a pressure transducer. The reaction rate is defined as the time taken for the pressure to rise from 100 to 300 psi. The mean reaction rate of five trials of the mixture is compared to the mean reaction rate of five trials of reference oxidizing liquids. Reference materials include a nitric acid (65% solution) mixture, a sodium chlorate (40% aqueous) mixture, and a perchloric acid (50% solution) mixture. The liquid is not considered an oxidizer if the rate of pressurization of the vessel is slower than the nitric acid (65% solution) mixture. A packing group for each material is assigned based on the reaction time of the mixture compared to the reference mixtures. If the sample material spontaneously ignites or exhibits a mean pressure rise time less than that of the perchloric acid mixture, the sample material is assigned to Packing Group I. If the sample material exhibits a mean pressure rise time less than or equal to that of the sodium chlorate mixture and does not fall under Packing Group I, the sample material is assigned to Packing Group II. If the sample material exhibits a mean pressure rise time less than or equal to that of the nitric acid mixture and does not fall under Packing Groups I or II, the sample material is assigned to Packing Group III.

Reference: Transport of Dangerous Goods – Tests and Criteria