Optical cells very high pressure

It can be used under very high pressure and temperatures. Oil reservoirs are found typically at 100°C and 300 atm pressure. The surface tension of such systems can be conveniently studied by using high pressure and temperature cells with optical clear windows (sapphire windows 1 cm thick up to 2000 atm). For example, yof inorganic salts at high temperatures (ca. 1000°C) can be measured using this method. The variation in surface tension can be studied as a function of various parameters (temperature and pressure additives [gas, etc.]). 

Optical cells can be designed for very high pressure of 1000 MPa and, more and temperatures from -273 to 800°C. 

The experimental conditions and results of the analysis of the purity of separated benzene crystals are shown in Table 1. In tests of No. 1-1 to 1-4, and 3-1 and 3-2, the melt was compressed to the pressure shown in Table 1 and kept on the same value, without seed crystals. Nucleation occured on the wall and crystals grew there. In tests of No.2-1, 2-2 and 3-3, seed crystals were made as described above they grew both inside the optical cell and on the wall. In these tests, since the melt around benzene crystals was replaced by the water, the crystals were taken out without serious destruction. The shapes of benzene crystals were dendritic, and purity of it was over 99.9 mole percent, independent from the operational conditions and the feed compositions as shown in Table 1. Therefore, crystals obtained by high pressxire crystallization is considered to be very pure due to the complete removement of mother liquid from crystal surface. 

We generally distinguish between two methods when the determination of the composition of the equilibrium phases is taking place. In the first method, known amounts of the pure substances are introduced into the cell, so that the overall composition of the mixture contained in the cell is known. The compositions of the co-existing equilibrium phases may be recalculated by an iterative procedure from the predetermined overall composition, and equilibrium temperature and pressure data It is necessary to know the pressure volume temperature (PVT) behaviour, for all the phases present at the experimental conditions, as a function of the composition in the form of a mathematical model (EOS) with a sufficient accuracy. This is very difficult to achieve when dealing with systems at high pressures. Here, the need arises for additional experimentally determined information. One possibility involves the determination of the bubble- or dew point, either optically or by studying the pressure volume relationships of the system. The main problem associated with this method is the preparation of the mixture of known composition in the cell. 

Very recently, Addleman et al. described a high-pressure cell for the study of TRLIF of uranyl complexes in supercritical CO2 (21). A schematic of the optical cell is shown in Figure 3. The cell has two perpendicular optical paths that are both orthogonal to the SCF flow, allowing absorption, fluorescence, and Raman measurements. The cell body was machined from stainless steel with an internal volume of 0.3 ml. The cell windows were made of 2-mm-thick synthetic... 

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