around the cell body. The complementary method does not change the temperature of the anvils and includes fine resistive heaters placed within the sample chamber and laser heating. The main advantage to resistive heating is the precise measurement of temperature with thermocouples, but the temperature range is limited by the properties of the diamond which will oxidize in air at 700 °C The use of an inert atmosphere can extend this range above 1000 °C. A tungsten wire resistive heater inside a BX90 DAC was reported to reach 1400 °C. With laser heating the sample can reach temperature above 5000 °C, but the minimum temperature that can be measured when using a laser-heating system is ~1200 °C and the measurement is much less precise. Advances in resistive heating are closing the gap between the two techniques so that systems can be studied from room temperature to beyond 5700 °C with the combination of the two. Gas loading Principle The pressure transmitting medium is an important component in any high-pressure experiment. The medium fills the space within the sample 'chamber' and applies the pressure being transmitted to the medium onto the sample. In a good high-pressure experiment, the medium should maintain a homogeneous distribution of pressure on the sample. In other words, the medium must stay hydrostatic to ensure uniform compressibility of the sample. Once a pressure transmitting medium has lost its hydrostaticity, a pressure gradient forms in the chamber that increases with increasing pressure. This gradient can greatly affect the sample, compromising results. The medium must also be inert, as to not interact with the sample, and stable under high pressures. For experiments with laser heating, the medium should have low thermal conductivity. If an optical technique is being employed, the medium should be optically transparent and for x-ray diffraction, the medium should be a poor x-ray scatterer – as to not contribute to the signal. Some of the most commonly used pressure transmitting media have been sodium chloride, silicone oil, and a 4:1 methanol-ethanol mixture. Sodium chloride is easy to load and is used for high-temperature experiments because it acts as a good thermal insulator. The methanol-ethanol mixture displays good hydrostaticity to about 10 GPa and with the addition of a small amount of water can be extended to about 15 GPa. For pressure experiments that exceed 10 GPa, noble gases are preferred. The extended hydrostaticity greatly reduces the