KERN EMB-V Operating Instructions Manual

KERN EMB-V Operating Instructions Manual Manual pdf 35 page image

EMB-V-BA-e-1210 359.2.3 LiquidsSolids are generally not sensitive to temperature changes, so that the correspondingdensity changes are not relevant. However, since you work with an aid liquid by thedensity determination of solids, according to the "Archimedean Principle", itstemperature is taken into account. The temperature change effects liquids greaterand causes changes in the density in order of 0.1 to 1 ‰ per °C. Hereby, the thirddigit after the decimal point is affected.9.2.4 SurfaceThe suspension bracket of the sample dish penetrates the surface of the fluid. Thisstate undergoes continuous change. If the sample or the sinker is relatively small,the surface tension will impair repeatability. The addition of a small amount ofdetergent makes the surface tension negligible andincreases repeatability.9.2.5 Sinker for density determination of liquids.To save test fluids by the density determination of liquids, a small glass beaker andan appropriate sinker is to be used. Hereto, it should be noted that a larger sinkerachieves greater accuracy.Determine the buoyancy and volume of the sinker as accurately as possible. For thedetermination of fluid density these results are applied to the common denominatoras well as the numerator of the formula.9.3 General information9.3.1 Density / Relative DensityRelative density follows from the weight of a specimen divided by the weight of water(at 4° Celsius) of the same volume. For this reason relative density does not have aunit. Density equals mass divided by volume.The application of the relative density instead of the density of a fluid in a formulaproduces an incorrect result. In the case of fluids only their density isphysically meaningful.9.3.2 Drift of Balance DisplayThe drifting of a balance does not influence the final result of the densitydetermination although the shown weight of weighing in air is affected. Accuratevalues are merely required if the density of fluids is determined by means of a sinker.When changing the ambient temperature or location, an adjustment of the balance isnecessary. Hereto, remove the density kit and carry out an adjustment with thestandard weighing plate (See chapter 6.6).