Krypton freezing point

Coasne et al.311 studied freezing and melting of a binary mixture of argon and krypton in a structureless slit pore. Comparison of the results with the bulk mixture are made. Interestingly it is found that the melting point increases in these systems compared to the bulk, in qualitative agreement with experiment. 

According to Dollimore and Heal (136), pores that appear to be 7-10 A in diameter by the conventional calculations from the nitrogen adsorption isotherm are actually only 4-S A in diameter. Submicropores in silica gel prepared from sol particles only 10 A in diameter are so small that even krypton cannot enter. It is known that monosilicic acid rapidly polymerizes to particles of about this size at low pH. Dollimore and Heal (172) prepared such gel by freeze-drying a 1% solution of mono-silicic acid. Since the evaporating and freezing removed much water, the pH of the system at the gel point was at 1-2, which is the point of slowest particle growth. The silica might be called porous because the pores were penetrated by helium (only). Helium also penetrates fused silica In the normal sense such silica is not porous. 

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