Density of organic liquids

Karelson, M. and Perkson, A. (1999). QSPR Prediction of Densities of Organic Liquids. Computers Chem., 23,49-59. 

THE MEASUREMENT OF SPECIFIC HEAT. VISCOSITY AND DENSITY OF ORGANIC LIQUID REACTOR COOLANTS AT ELEVATED TEMPERATURES. 

Values for the density of pure liquids can usually be found in the handbooks. It should be noted that the density of most organic liquids, other than those containing a halogen or other heavy atom , usually lies between 800 and 1000 kg/m3. Liquid densities are given in Appendix C. 

The properties of organic liquids relevant to their use as solvating agents have also been reviewed [76]. The ability of liquids to solvate a solute species depends mainly on their polarity and polarizability properties, ability to hydrogen bond, and cohesive electron density. These molecular properties are best measured by the Kamlet-Taft solvatochromic parameters, and the square of Hildebrand s solubility parameter. 

Ionic liquids have higher densities than organic liquids, and thus exist as the lower phase in a biphasic system. They are also generally more viscous than conventional organic solvents the phase separation from organic solvents is often more rapid than with two solvents of similar viscosity. 

The y values of aqueous solutions generally increase with different electrolyte concentrations. The magnitude of y of aqueous solutions containing organic solutes invariably decreases. As mentioned earlier, the surface of a liquid is where the density of the liquid changes to that of a gas by a factor 1000 (Chapter 1, Figure 1.1). 

Solvent Strength of Pure Fluids. The density of a pure fluid is extremely sensitive to pressure and temperature near the critical point, where the reduced pressure, P equals the reduced temperature, Tr, =1. This is shown for pure carbon dioxide in Figure 2. Consider the simple case of the solubility of a solid in this fluid. At ambient conditions, the density of the fluid is 0.002 g/cm3. Thus the solubility of a solid in the gas is low and is given by the vapor pressure over the total pressure. The solubilities of liquids are similar. At the critical point, the density of C02 is 0.47 g/cm3. This value is nearly comparable to that of organic liquids. The solubility of a solid can be 3—10 orders of magnitude higher in this more liquid-like C02. 

Two solid forms, distinguished as a- and /3-modifications, were described by Marignac 3 and others 4 and axe now generally recognised. The a- or ice form is that corresponding with ordinary moltbn sulphur trioxide it consists of colourless prismatic crystals which melt at 16-8° C. to a fairly mobile liquid, less viscous than sulphuric acid. The pure liquid is colourless, but the presence of organic matter causes a brown coloration. The density of the liquid has been found to be as follows ... 

The heat of combustion of hexane, C6H14(1), is —4163 kj-mol Use this fact and the values for the enthalpies of combustion of various organic compounds found in Table 6.3 to compare benzene, ethanol, hexane, and octane as possible fuels by doing the following, (a) Calculate the heat produced per gram of each of these substances, (b) From standard reference sources, find the density of each liquid and determine the heat produced per liter of liquid. 

A certain beaker has a mass of 141.2 g. When 13.0 mL of an organic liquid is placed in the beaker, the total mass is 150.5 g. Calculate the density of the liquid to the proper number of significant digits. 

The densities and coefficients of expansion of a number of organic liquids determined by Kopp and by Pierre are given in terms of the equation ... 

If the wavelength of the ultrasound exceeds 8 mm, the maximum volume of a liquid drop is no longer dictated by the above-described ratio but by that between hydrostatic pressure and the capillary pressure due to surface tension inside the drop. If this ratio, which is referred to as the Bond number of the levitated drop, exceeds 1.5, the drop disintegrates. Therefore, the maximum volume of a drop is a function of the surface tension and specific density of the liquid. For example, the maximum volume of a water drop is 155 pi for most organic solvents, it is about 40 pi [111]. 

Figure 8.20. Optical density curves for various mixtures of organic liquids. From left to right 1,2-dichlorobenzene/heptane 1,2,4-trichlorobenzene/heptane potassium hydrogen phthalate in water hydroquinone/ethanol, and 2-naphthol/hexanol. (Adapted from Reference 14 with permission.)...

Applicability Saturated liquid densities of organic compounds. 

Liquid-liquid phase equilibria are most often measured by the analytic method mentioned above, although the synthetic method is used on occasion. Issues of sampling and equilibration are again important. If the densities of the liquid phases are similar, it can be difficult to achieve separation. Entrainment of one phase in the other is a particular problem in aqueous/organic systems, where emulsions can form. For nonpolar solutes like hydrocarbons in water, the solubility is so small that analysis becomes difficult, and even a tiny amount of contamination with the hydrocarbon phase cannot be tolerated. Reviews exist [87, 90, 95] describing apparatus for measuring liquid-liquid equilibria at near-ambient pressures. 

There exist a number of familiar procedures for effecting mineral separations, including sink-float methods based on density differences and froth flotation based on wettability. Because of the tendency of kerogen to swell and soften in the presence of organic liquids and thus possibly to mobilize trapped mineral particles, and because most minerals are water-wetted and thus extractable with water, we investigated a liquid-liquid (oil-water) pelletization method. 

Solid Density Prediction The prediction of solid density is an inexact science and sometimes is taken as the liquid density at the triple point, although the solid density normally is higher than this value with a discontinuity at the triple point. Based on sohd density data reviewed for the DIPPR compilation, the solid density at the triple point can be estimated for organic compounds as 1.17 times the liquid density at the triple point. As liquid density at low temperatures varies little with temperature, the density of the liquid at the lowest estimable point above the triple point can be used with little degradation of the result. As solid density only decreases very slightly with increasing temperature and very little data on solid density as a function of temperature exist, no methods have been developed for predicting the solid density vs. temperature. 

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