This book summarizes the results of the experimental studies of phase relations in the chemical systems relevant to Earth,carried out by the author in a time - riod of over 20 years between 1979 and 2001.It is based on 1000 piston-cylinder experiments at pressures up to 4 GPa,and close to 700 experiments carried out with a multi-anvil apparatus at pressures up to 24 GPa. The emphasis in these studies was on internal consistency. Large sets of data were produced using the same sample assembly,high-pressure apparatus,experimental procedures and calibrations by the same experimentalist to maximize the internal consistency. The results were published in 69 peer- reviewed articles