The Decomposition of Nitrate Crystals by Ionizing Radiations

Abstract

Sodium nitrate, potassium nitrate, and potassium chlorate have been exposed two to four weeks in the experimental thimble of the Argonne Heavy Water Pile. After exposure these salts evolve a gas when dissolved in water or when melted or heated to a crystal transition point. The gas yields are in sodium nitrate ca 0.3, in potassium nitrate ca 0.8, and in potassium chlorate 2.0–3.0 molecules gas/100 ev. For the nitrates this gas has been shown to be largely oxygen which is trapped during irradiation in the gaseous form in small pockets in the crystal. This conclusion is based on the paramagnetism of the irradiated crystals, on chemical analysis of the evolved gases, and on measurements of the amounts of gas liberated in crushing experiments. When irradiated crystals are heated below the melting point, the gas pockets grow and coalesce, this being accompanied by a decrease in crystal density. In irradiated nitrates, oxygen and nitrite ion are formed in equivalent amounts. Experiments with low energy x‐rays indicate that most of the decomposition results from electronic ionization and excitation and not from elastic collision of the bombarding particles.