Measurement hydrometer

Because of their widespread use for simple process control, hydrometers are frequently calibrated, not in specific gravity, but in some units related to it, which bear (or bore at one time) some relationship to the concentration being so measured. 

Density is generally measured at 15°C using a hydrometer in accordance with the NF T 60-101 method it is expressed in kg/1 with an error of 0.0002 to 0.0005 according to which category of hydrometer is utilized. However, in practice only three decimal places are usually retained. 

The API gravity of water is 10°. A light crude oil would have an API gravity of 40°, while a heavy crude would have an API gravity of less than 20°. In the field, the API gravity is readily measured using a calibrated hydrometer. 

The oil density at surface is readily measured by placing a sample in a cylindrical flask and using a graduated hydrometer. The API gravity of a crude sample will be affected by temperature because the thermal expansion of hydrocarbon liquids is significant, especially for more volatile oils. It is therefore important to record the temperature at... 

The density of the electrolyte, measured by a hydrometer, forms a useful indicator of the state of charge or discharge of the battery. 

Density. Measurement of density is widely used in the sugar industry to determine the sugar concentration of symps, Hquors, juices, and molasses. The instmment used is called a hydrometer or a spindle. When it is graduated in sucrose concentration (percent sucrose by weight), it is called a Brix hydrometer or a Brix spindle. Brix is defined as the percent of dry substance by hydrometry, using an instmment or table caUbrated in terms of percent sucrose by weight in water solution. Hydrometers are also graduated in °BaumH, stiU in use in some industries. The relationship between °BaumH and density, ing/cm, is °Baumn Baum e = 145(1 — 1/d). 

NaOH titration using phenolphthalein hydrometer measurement evaporation and weighing... 

The deterrnination of the proof (the alcohol content) is us uaHy made by measuring specific gravity with hydrometers at the standard temperature of ... 

Flussigkeits-. liquid, fluid, hydraulic, hydrostatic. -bad, n. liquid bath, -dichtemesser, m. hydrometer, -druck, m. pressure of a liquid, hydrostatic pressure, -ffirderung, /. conveyance of liquids, -gemisch, n. mixture of liquids, liquid mixture, -grad, m. degree of fluidity viscosity. -gradmesser, m. viscosimeter. -Unse, /. (Micros.) immersion objective, -mass, n. liquid measure, -menge. 

H2SO( concentration during use of a lead cell provides the basis for the convenient hydrometer test of the state of discharge of an automobile battery. The hydrometer measures the density of the electrolyte solution, thus indicating how much of the H2SOi has been consumed. Obviously, this method cannot be used to check an Edison cell since the electrolyte concentration is constant. 

Mix 400 mL of pure concentrated hydrochloric acid with 250-400 mL of distilled water so that the specific gravity of the resultant acid is 1.10 (test with a hydrometer). Insert a thermometer in the neck of a 1 L Pyrex distillation flask so that the bulb is just opposite the side tube, and attach a condenser to the side tube use an all-glass apparatus. Place 500 mL of the diluted acid in the flask, distil the liquid at a rate of about 3-4 mL min-1 and collect the distillate in a small Pyrex flask. From time to time pour the distillate into a 500 mL measuring cylinder. When 375 mL has been collected in the measuring cylinder, collect a further 50 mL in the small Pyrex flask watch the thermometer to see that the temperature remains constant. Remove the receiver and stopper it this contains the pure constant boiling point acid. Note the barometric pressure to the nearest millimetre at intervals during the distillation and take the mean value. Interpolate the concentration of the acid from Table 10.5. 

DIVER METHOD- This is a modification of the hydrometer method. Variation in effective density i and hence concn, is measured by totally immersed divers. These are small glass vessels of approximately streamline shape, ballasted to be in stable equilibrium, with the axis vertical, and to have a known density slightly greater than that of the sedimentation liq. As the particles settle, the diver moves downwards in hydrodynamic equilibrium at the appropriate density level. The diver indicates the position of a weight concn equal to the density difference between the diver and the sedimentation liq. Several divers of various densities are required, since each gives only one point on the size distribution curve... 

In gravity settling the sample is dispersed in a liquid and then allowed to settle in a sedimentation cell. The height of the particles in the cell is then measured, or the specific gravity of the dispersing liquid is measured at different time intervals, which gives an indication of the size distribution. The hydrometer, or Bouyoucos, method is frequently used to classify the amount of sand, silt, and clay in soils. 

The common technique used to measure the API gravity of a hquid sample is with a hydrometer graduated in degrees of API gravity. The hydrometer is inserted in the liquid sample and allowed to float freely. When equilibrium is reached, the API gravity may be read from the exposed portion of the hydrometer. 

For solid and semisolid materials, a pycnometer is generally used (ASTM D70), and a hydrometer is applicable to liquid materials (ASTM D3142). It is worthy of note at this point that the density (hence, the API gravity) of residua show pronounced changes due to the effects of temperature and pressure (Table 11.1). Therefore, isolation of the sample after leakage or spillage must also allow for equilibration to ambient conditions before measurements are made. 

Hydrometer. A device for measuring specific gravity of liquids. Its description with Fig is given in Vol 3 of Encycl, p D67, under DENSITY AND SPECIFIC GRAVITY... 

The thermal expansion coefficient governs the influence of temperature on density and therefore it is necessary to specify temperature when discussing density or specific gravity. The density of milk is of consequence since fluid milk is normally retailed by volume rather than by mass. Measurement of the density of milk using a hydrometer (lactometer) has also been used to estimate its total solids content. 

In addition to lactometry (determination of the extent to which a hydrometer sinks), the density of milk can be measured by pycnometry (determination of the mass of a given volume of milk), by hydrostatic weighing of an immersed bulb (e.g. Westphal balance), by dialatometry (measurement of the volume of a known mass of milk) or by measuring the distance that a drop of milk falls through a density gradient column. 

Normally a stem or hydrometer is used to determine density. Hydrometers may be scaled in many different units. In the United States, grape juice and wine densities are usually measured in Brix or Balling degrees which are density units reflecting the weight per cent of sucrose in sucrose-water solutions. 

As densities vary with temperature, and as hydrometers are calibrated to be accurate at different temperatures, the fermenting solution should be warmed or cooled to near the calibration temperature for the particular hydrometer used for precise determinations, the actual temperature should be measured and the measured density should be corrected. 

Bearing in mind, from the discussion above, that °Brix really only allows estimation of relative water content in a series of related systems, this measure is used sufficiently frequently to require that the procedures be outlined. The sections below describe the use of the refrac-tometer and the hydrometer for determining water concentration. These instruments are readily available from a number of sources including Brannan and ERTCO Precision (for... 

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