Measuring Densities of Solids and Liquids Using Magnetic Levitation: Fundamentals

This paper describes an analytical system that uses magnetic levitation to measure densities of solids and water-immiscible organic liquids with accuracies ranging from ±0.0002 to ±0.02 g/cm3, depending on the type of experiment. The technique is compatible with densities of 0.8−3 g/cm3 and is applicable to samples with volumes of 1 pL to 1 mL; the samples can be either spherical or irregular in shape. The method employs two permanent NdFeB magnets positioned with like poles facing one anotherwith the axis between the poles aligned with the gravitational fieldand a container filled with paramagnetic medium (e.g., MnCl2 dissolved in water) placed between these magnets. Density measurements are obtained by placing the sample into the container and measuring the position of the sample relative to the bottom magnet. The balance of magnetic and gravitational forces determines the vertical position of the sample within the device; knowing this position makes it possible to calculate the density of the sample.

本文介绍了一种分析系统，该系统通过磁悬浮技术测量固体及不与水混溶的有机液体的密度，其测量精度可达±0.0002至±0.02 g/cm³，具体取决于实验类型。该技术适用于密度在0.8−3 g/cm³范围内的物质，并能处理体积从1 pL至1 mL的样品；样品形状可为球形或不规则。该方法采用两个永久性NdFeB磁铁，其极性相同且相对放置，磁铁之间的轴线与重力场方向一致，并在两磁铁之间放置一个装有顺磁性介质（例如，溶解于水中的MnCl2）的容器。通过将样品置于容器中并测量样品相对于底部磁铁的位置来获得密度测量值。磁力与重力力的平衡决定了样品在装置中的垂直位置；了解这一位置便可以计算出样品的密度。