"This pioneering study discusses the computations of the structure of the assembled piston-cylinder type chamber for plotting the ice diagram in P-T coordinate at high pressure (0-2500) MPa and low temperature (90-300) K and measuring the temperature, pressure of the sample, cracks in the chamber at a temperature of 100 K, a pressure of 3000 MPa, broken pictures of the piston are shown. For the first time the dependence of the thermal, baric and thermal compressibility coefficients of pressure and temperature of the ice-twelve modification on the phase diagram obtained in practice was studied. We constructed the graphs of the dependence of the thermal coefficient of ice-twelve modification on pressure, the dependence of the partial derivatives of the ice-twelve modification on temperature, the dependence of the coefficients of thermal expansion of the ice-twelve modification on temperature. We also developed results that between the studied temperature and pressure, the values of , do not change much as a function of temperature at constant pressure and pressure at constant temperature, the value of decreases with increasing pressure of the ice modification under consideration at the same temperatures. "