We have determined the melting temperature of formic acid(HCOOH) to 8.5 GPa using infrared absorption spectroscopy, Raman spectroscopy and visual observation of samples in a resistively heated diamond-anvil cell. The experimentally determined melting curve compares favorably with a twophase thermodynamic model. Decomposition reactions were observed above the melting temperature up to a pressure of 6.5 GPa, where principal products were CO 2 , H 2 O and CO. At pressures above 6.5 GPa, decomposition led to solid-like reaction products. Infrared and Raman spectra of these recovered products indicate that pressure affects the nature of carbon-carbon bonding.

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We have studied cyanuric acid (H(3)C(3)N(3)O(3)) at static pressures up to 8.1 GPa and simultaneous temperatures up to 750 K, using primarily infrared absorption spectroscopy and visual observation. The corresponding phase diagram compares favorably with theoretical predictions of metastable organic materials. Two reactions were observed and characterized; both are irreversible. Below 2 GPa, melting is accompanied by a decomposition reaction, and upon cooling, cyanuric acid is not recovered. Above 2 GPa, heating results in a solid product recoverable at ambient conditions. Corresponding infrared spectra suggest that pressure leads to the formation of heterocycles of increasing complexity and biological potential, with the composition determined by the pressure of formation. Cyanuric acid is of interest at these conditions because it and its monomer, isocyanic acid, are "prebiotic" compounds found in stellar dust clouds, meteorites, and other remnants of the early Earth.

We have developed an experimental method to obtain the coefficient of friction between diamond and metal under high confining pressure in the diamond anvil cell. A metal ring is compressed between the diamond anvils and its inner and outer diameters are measured as a function of the compression. Measured dimensions are then compared to the results of finite element simulations, in which the coefficient of friction is a free parameter. As an example, we apply the method to polycrystalline molybdenum up to a hydrostatic pressure of 6GPa.