Liquid and Gaseous Carbon

The freeze-thaw valve is a recently developed microvalving system [34,35]. Unlike all other valving systems it does not require any moving parts in the capillary channel and has no dead volume. A small section of fluid inside the capillary is made to act as its own shut-off valve upon freezing. The freezing process was achieved by using a fine jet of a mixture of liquid and gaseous carbon dioxide at... 

In the conormative research project, preconditioning with liquid and gaseous carbonation of the cement materials was tested. The preconditioning consists of wet contact with several water types (soft and moderate hardness) or dry contact with CO2 imder several conditions (C02-pressure, time). The effect of preconditioning is compared with unpreconditioned cement mortar specimens. 

The p T) phase diagram of carbon dioxide is presented in Fig. la [21]. On the vapor pressure curve (Ig) a liquid (1) and a gaseous (g) phase coexist. With increasing pressure the vapor pressure curve rises and ends at the critical point CP ((304.1282 0.015) K, (7.3773 0.0030) MPa, (0.4676 0.0006) g cm [22]), where the two coexisting phases (1 and g) become identical. With decreasing pressures it ends at the triple point Tr (216.58 K, 0.5185 MPa [22]), where solid, liquid, and gaseous carbon dioxide are in equilibrium. The sublimation pressure curve (gs) and the melting pressure curve (Is) are not important within the scope of the present chapter. 

Imagine an experiment in which liquid and gaseous carbon dioxide are sealed in a thick-walled glass vessel at 20°C. At this temperature, the liquid is in equilibrium with its vapor at a pressure of 57 atm. You observe that the liquid and vapor are separated by a well-defined boundary, or meniscus. Now suppose the temperature is raised. The vapor pressure increases, and at 30°C it is 71 atm. Then, as the temperature approaches 31°C, a curious thing happens. The meniscus becomes fuzzy and less well defined. At 31°C,... 

As we saw in Section 5.1, a single substance can exist in different phases, or physical forms. The phases of a substance include its solid, liquid, and gaseous forms and its different solid forms, such as the diamond and graphite phases of carbon. In one case—helium—two liquid phases are known to exist. The conversion of a substance from one phase into another, such as the melting of ice, the vaporization of water, and the conversion of graphite into diamond, is called a phase transition (recall Section 6.11). 

The most widely used form of the carbonaceous fuels is perhaps the solid fuel, coal. Though occurring basically in the solid form, coal can be converted to both liquid and gaseous forms. In the solid form, coal is basically of two types charcoal (prepared by carbonization of wood) and mineral coal (obtained from coal mines). Coal is found on every continent,... 

Three processes that take place in living organisms - respiration in animals and plants, photosynthesis only in plants, and the precipitation of solids by some aquatic animals - have altered the primeval composition of the outer solid, liquid, and gaseous layers of the earth. Respiration consumes oxygen from the atmosphere and creates carbon dioxide. Photosynthesis, which does the opposite (consumes carbon dioxide and releases oxygen), has... 

Radiolysis of CO, both in the liquid and gaseous states, also leads to C02 and C302 formation, the latter product appearing mainly as a polymeric solid23-27. A scheme of reactions consisting of the initial production of a carbon and an oxygen atom, followed by (10)-(12) and... 

The combustion of 1 mol of solid urea to liquid water and gaseous carbon dioxide and nitrogen (N2) in a bomb colorimeter at 25°C (constant volume) liberated 666 kj of heat energy. Calculate AH, the change in heat content (enthalpy), for this reaction. 

Figure 3 shows the effect of coal particle residence time on the fraction of carbon converted to liquid and gaseous products. Based on this correlation, the production of gaseous products appears to be less sensitive to coal residence time than the production of liquids. It also appears that the production of liquids is favored by shorter residence time. 

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