A Simple Device for Making Constant Density Gradients

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Abstract
The possibility of adapting the well-known mixing device shown in Fig. 1 for production of density gradients with retained hydrostatic equilibrium is investigated. It is shown that a specific form of the unstirred container can be found that gives a strictly linear density course. Instead of specifically shaped containers, specific plungers can be used in cylindrical containers. All pertinent equations arc given. The modified arrangement is useful for falling as well as for rising densities by use of exchangeable plungers. The communicating duct between the containers has to have a large bore. With the aid of a V-shaped channel in a stopcock, turnable to a A orientation, hydrostatic stability can be retained under all circumstances. In the experimental section it is shown that accurately constant density gradients are really obtained by using plungers constructed according to the requirements of the theory. It is also shown that, under certain conditions, approximately constant density gradients can be obtained by the use of cylindrical containers with free cross-sectional areas proportional to the densities of the liquids in them.