Test Procedures and Classification Criteria for Release of Toxic Gases from Water-Reactive Materials (2014)

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6C H A P T E R 3 The principal outcome from this research is a complete, detailed, and reproducible test method for measurement of the rate at which gas is produced when a water-reactive sub- stance is combined with water under controlled conditions in the laboratory. This is the “revised test procedure applicable to substances that evolve both toxic and flammable gases” called for in Task 4 of HMCRP Project HM-14. In developing this “improved test methodology,” a test has been produced that can encompass substances that produce toxic gas as well as substances that produce flammable gas; furthermore, this test is clearly defined and specified in ways that should enable reproducible, cross-laboratory implementation. A complete description of the test, test apparatus, and testing results can be found in Appendix A. In brief, the test method developed and described herein determines the rate at which flammable gas or toxic gas is produced when a sub- stance is combined with water, under laboratory conditions, in a closed vessel, by monitoring the change in pressure as a function of time after the substance and water are mixed. Pres- sure changes are converted to changes in volume by applying a calibration relationship relating change in pressure within the apparatus to amounts of gas (as measured at ambient laboratory conditions) added to the vessel. The test proce- dure, by default, considers the addition of the test substance to an excess of water. However, when conditions dictate—for instance, if observation of gas production is prevented by absorption of gas by water present in the apparatus—there are provisions for reversing the order of addition. A specific apparatus is described in Appendix A, but the apparatus may vary from the apparatus described there. Whatever the specifics of the apparatus, however, it must meet the following criteria: • Be gas tight and capable of safely withstanding internal pressures of at least 50 kPa gauge. • Allow for the safe combination of water with a water-reactive substance. Provisions for this must include, but are not limited to, pressure relief of the apparatus at a pressure above 50 kPa gauge yet safely below a pressure at which the vessel might rupture; appropriate personal protective equipment for labo- ratory personnel; and an appropriate laboratory workspace to house the apparatus including fume hoods, proper hazard communication procedures for laboratory personnel, and supervision and operation by qualified personnel. • Accommodate addition of the substance to water as well as, when required, the reverse order of addition. • Be capable of use with both solid and liquid substances. • Include accurate and precise monitoring of pressure as a function of time during testing, preferably using electronic data logging at intervals as short as 2 seconds, with a pres- sure resolution greater than 0.1 kPa. • Accommodate calibration of the response of pressure to the volume of gas added to or produced within the apparatus to provide for conversion from observed pressure increases within the apparatus to volume of (as measured at ambient conditions of temperature and pressure) gas added to or produced within the apparatus (this may, for instance, be accomplished via the addition of known aliquots of gas at ambient pressure). • Allow, when the reactivity of the test substance warrants, for testing to occur under an inert atmosphere. The procedure (again, in summary) then encompasses the following steps: • The apparatus is charged with water, or for some sub- stances (determined by test), with the test substance. • The pressure/volume (P/V) response and calibration of the apparatus is checked. • The apparatus is then charged with the test substance (or for some substances—water—as determined by test), and test substance and water are combined. • The pressure produced as any reaction proceeds is mea- sured precisely and accurately as a function of time. Findings and Applications

7 • The pressure-versus-time results are converted to a specific rate of gas production (liters of gas per kg of substance reacting per hour or per minute) utilizing the pressure/ volume response calibration. • The testing steps listed above, except for the P/V calibration, are repeated to obtain a total of five results, which are then averaged to find final results and sample standard deviation. • Specifics of the results are then evaluated. The results may be reported as is, unless there is evidence that water present in the flask is masking gas evolution and/or that observed gas evolution merely reflects evaporation of the test sub- stance. If that is the case, then repeat the procedure with the apparatus first charged with test substance, and then aliquots of water added to it, and report those results. Note that, in this latter case, the specific rate of gas evolution will be based upon an estimate of the amount of the substance present that might (according to chemical principles) have reacted with the water added. It is not, in that case, based on the total amount of test substance present. In order to validate the test (i.e., to establish reproducibil- ity and precision of the test within a single laboratory) and to test the method with a range of representative materials, a series of substances were characterized. The results are shown in Table 3-1. The tasks for HMCRP Project HM-14 called for several other deliverables to be included in this report; these deliver- ables, along with some other supplementary material, can be found in Appendices A through C. A listing of Appendices A through C and the HMCRP Project HM-14 tasks they fulfill is provided in Table 3-2. Table 3-1. Validation testing results. Material Approach Result (l/kg-min) Standard Deviation (l/kg-min) Relative Standard Deviation UN Number (CH3)2SiCl2 B 36 8 22% 1162 NaNH2 A 9600 2000 20% 1390 NaBH4 A 2 (120 l/kg-h) 0.5 (30 l/kg-h) 25% 1426 CH3COCl B 665 60 9% 1717 AlCl3 A 7500 1700 23% 1726 POCl3 A, B 1–3000 (& up) n/a n/a 1810 SiCl4 A 1020 210 20% 1818 SOCl2 B 370 110 30% 1836 TiCl4 A 5500 900 16% 1838 Mg3N2 A 7900 1800 23% 3132 A = Substance added to water, B = water added to substance Deliverable Task Appendix Full Technical Test Description Task 7 Appendix A Proposed Classification System Tasks 5 & 7 Appendix B ASTM Format Test Procedure Task 7 Appendix C Table 3-2. Appendices A through C.