Measuring the Density of Liquids

What is the density of a iiquid if, after it is placed in a graduated cylinder that weighs 81.42 g, the iiquids reaches the 48.2 mL level and the cylinder with the liquid in it weighs 133.89 g  

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The purpose of this compilation is to tabulate the densities of compounds, hence only minimal description of experimental methods used to measure the density of liquids or solids appears. Detailed descriptions of methods for density determination of solids, liquids and gases, along with appropriate density reference standards, appear in a chapter by Davis and Koch in Physical Methods of Chemistry, Volume VI, Determination of Thermodynamic Properties [86-ros/bae],... 

The principal experimental method used to measure the density of a solid is determination of the mass of liquid displaced by a known mass of solid. It is essential that the solid have no appreciable solubility in the liquid, that all occluded air be removed from the solid and that the density of the displacement fluid be less than that of the solid lest the solid float. Densities of crystalline solids also can be determined from the dimensions of the unit cell. Davis and Koch discuss other methods for measuring the density of liquids and solids such as hydrostatic weighing of a buoy and flotation methods. 

A hydrometer is a very simple device used to measure the density of liquids such as urine or milk. A typical hydrometer has a weighted end to keep it upright in the liquid of interest. These devices are also usually calibrated. When placed in a liquid, a hydrometer will sink until it displaces an amount of fluid exactly equal to its weight. If the fluid is dense, it will displace only a small amount of fluid, and thus not sink very deep. If the density of the fluid is not very high, the hydrometer will sink deeper. The user simply reads the liquid density from the calibrated scale in the neck of the hydrometer. Two examples are shown in Figure 5.5. The fluid on the left has a greater density than the fluid on the right. 

A device used to measure the densities of liquids and solutions. 

Density measurements are extremely Important in industry, because a large amount of information can be obtained about a material with a reasonably simple measurement. By measuring the density of liquids, we can determine how much electrical charge is in your car battery, at what temperature your radiator will freeze, the salt content of a pickling brine, the alcohol content of a brandy, and certain diseases from urine samples. The densities of solids can tell us the hydration degree and porosity of Portland cement, the cotton-polyester blend in a fabric, the velocity of detonation of... 

Three experimental studies were conducted by Japanese researchers in 1971-1974 and were not published. They became known recently from Ref. [0.51]. They include the work of Kumagi and Iwasaka [3.48], who measured the density of liquid Freon-22 in the interval T = 253-313 K at pressures up to 160 MPa. 

In practice pycnometry can be used to measure the density of liquid polymers by placing them in a cup of known volume and mass. A cover containing a capillary through which the overflow can pass for removal is typically added. Since both the volume of the cup as well as the density of the liquid adhesive are temperature dependent, accurate readings require that temperature be carefully controlled for the test. The standard cup can be filled with a liquid adhesive that is below the desired test. Then the cup and adhesive are heated to the temperature at which the density is to be determined, and the mass is determined after the excess is wiped from the overflow orifice (ASTM-D1875-03 2003). 

The °AP1 gravity measures the density of a hydrocarbon liquid. Specific gravity (SG) is another common measurement of density. The liquid SG is the relative weight of a volume of sample to the weight of the same volume of water at 60°F (15.5°C). 

The density of a material is a function of temperature and pressure but its value at some standard condition (for example, 293.15 K or 298.15 K at either atmospheric pressure or at the vapor pressure of the compound) often is used to characterize a compound and to ascertain its purity. Accurate density measurements as a function of temperature are important for custody transfer of materials when the volume of the material transferred at a specific temperature is known but contracts specify the mass of material transferred. Engineering applications utilize the density of a substance widely, frequently for the efficient design and safe operation of chemical plants and equipment. The density and the vapor pressure are the most often-quoted properties of a substance, and the properties most often required for prediction of other properties of the substance. In this volume, we do not report the density of gases, but rather the densities of solids as a function of temperature at atmospheric pressure and the densities of liquids either at atmospheric pressure or along the saturation line up to the critical temperature. 

The density of an irregularly shaped solid is usually determined by measuring the mass and then measuring the volume of liquid that it displaces. The volume of liquid in a graduated cylinder is measured before the object is submerged and then measured again with the object submerged. The difference in the volume equals the volume of the object. 

A convenient way to measure the density of a liquid is to pump it slowly through a vertieal pipe and measure the differentia] pressure between the top and the bottom of the pipe. This differential head is directly related to the density of the liquid in the pipe if frictional pressure losses are negligible. 

An iron deficiency could be accommodated by a defect structure in two ways either iron vacancies, giving the formula Fe] /D, or alternatively, there could be an excess of oxygen in interstitial positions, with the formula FeOi+ f. A comparison of the theoretical and measured densities of the crystal distinguishes between the alternatives. The easiest method of measuring the density of a crystal is the flotation method. Liquids of differing densities which dissolve in each other, are mixed together until a mixture is found that will just suspend the crystal so that it neither floats nor sinks. The density of that liquid mixture must then be the same as that of the crystal, and it can be found by weighing an accurately measured volume. 

Specific gravity (sp gr) is a measure of the relative weight of one liquid compared to a universally familiar liquid, generally water. More specifically, sp gr is a ratio of the density of a liquid divided by the density of liquid water at 16°C (60°F). Specific gravities of selected liquids are shown in Table 1. 

When the boiling point of the liquid becomes constant, change the receiver and distil 100 ml of the liquid into the new receiver. Measure the density of the liquids in the receiver and in the Wurtz flask. What is the hydrogen chloride percentage in them Define an azeotropic mixture. 

The most convenient method of measuring the density of crystals is to suspend them in a liquid mixture, the composition of which is adjusted by adding one of the constituents until the crystals neither float nor... 

In multiphase flow metering, it is usually required to distinguish hydrocarbon from water. If the liquid phase is "oil continuous," the water fraction can be determined by dielectric constant measurement at microwave frequencies because the dielectric constant of dry hydrocarbon is on the order of 2 to 4 and that of water is 82. Naturally, density measurement can also distinguish water from oil. The next requirement is to distinguish the flow of liquid from the flow of gas in a system where the two will try to separate and travel at different velocities. Cross-correlation by nuclear techniques can measure the density of the stream twice (a short vertical distance apart) and correlate the fluctuations in density with time to determine velocity. Multiphase flow metering is a new and evolving technology,... 

Most measurements of densities of liquids below their normal boiling points are made in the presence of air. Densities reported here refer to liquids in equilibrium with a gas phase consisting of a mixture or air and vapor at a total pressure of one atmosphere below the normal boiling point and of vapor at the equilibrium vapor pressure above the boiling point. Thus air is not regarded as an impurity. The effect of dissolved air and other gases on the densities of liquid hydrocarbons has been reported by Ashcroft and Ben Isa [97-ash/ben], The differences they observed between the density of a liquid saturated with air at 1 atm and 298.15 K and the air free liquid are shown in Table 1. 

Interfacial tensions between coexisting liquid and supercritical gas phases for the a-tocopherol/carbon dioxide system have been measured for different pressures at 313, 333, 343, 353, 363, 373, 383, 393 and 402 K. At each interfacial tension measurement the density of both the liquid and the supercritical gas phase was also determined as these values are essential in calculating interfacial tensions from the shape and size of drops. Densities of the system investigated have already been measured by other authors [4, 6, 7] and their results agree, within measurement accuracy, with those obtained in this work. 

Detectors capable of continuously measuring the density of the flowing liquid have been designed by Kratky et al. [146]. They are based on the measurement of frequency oscillations of a quartz tube through which the eluate flows. The oscillation frequency depends on the tube mass and, thus, for the given eluent, on the concentration and density of the solute. Their application to size exclusion chromatography has been described by Trathnigg and Jorde [147]. Kirkland applied such a detector for FFF [148]. 

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