Density measurements of the lithium fluoride/lithium sulfide eutectic at high temperature
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to suspend it. The other end of the wire is attached to a balance sufficiently accurate to measure differences on the order of 0.01 --- 0.005 g. The balance is supported directly above the salt bath and is capable of being lowered toward the bath by means of a scissor jack. In accordance with the method reported by Janz and Lorenz, t~l the following convention is used for the experimental variables of interest: rest weight, Wr, is the measured weight of the density bob suspended above the bath in an argon atmosphere; contact weight, We, is the measured weight of the density bob when the pin first contacts the molten salt bath and is representative of the surface tension effect of the liquid at a given temperature; and, immersed weight, Wj, is the measured weight of the density bob immersed in the salt bath to a specific depth. Observed variations in the immersed weight with step changes in temperature correspond to changes in density of the liquid eutectic. By slowly lowering the balance toward the salt bath, the rest weight, W,, contact weight, We, and immersed weight, Wi, of the density bob can be measured. The immersion depth of the density bob is 3.81 cm below the point of contact between the fiat end of the pin and the salt bath. The surface tension effect on the emergent stem of the density bob, measured in grams, acts to increase the weight observed on the balance and is given by S = (We - W,)(d,/dp)
[11
The measured immersed weight, Wi, can now be corrected for the surface tension effect on the emergent stem to give the actual immersed weight, W,, as w. = w, - s
[2]
The density, P, of the liquid in question at a given temperature is given by p = (W,-
Wo)/V~
[3]
where the volume, Vr, at a specific temperature is determined using the known thermal expansion coefficient of 316 stainless steel and a measurement of the immersed volume of the bob at room temperature, V0. The value of V0 is determined with reference liquids of known densities. The volume of the density bob at room temperature, Vo, was determined using water, isopropanol, and acetone as reference liquids. The data for the weight measurements and calculated values for V0 are presented in Table I. The mean value for V0 was found to be 4.46 mL. Using 1.89 x 10-5 cm/(cm)(K) as the thermal expansion coefficient of series 316 stainless steel in the temperature range of interest, tsl the volume, Vr, of the density bob at elevated temperatures was established. For the determination of molten salt density, the procedure given above was followed for the first experimental point at the lowest temperature within the range of interest. The rest and contact weights measured for this point were carried through for all other temperatures. This is justified given the small magnitude of the surface tension effect relative to the immersed weight; changes of the surface tension effect with temperature are within the experimental error of this system. Thereafter, the bob was allowed to remain immersed in the VOLUME 25B, OCTOBER 1994--773
Table II.
Data from M
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