A Westphal balance (also known as a Mohr balance) is a scientific instrument used to measure the density of liquids.Mohr-Westphal balance, Virtual Museum of the History of MineralogyWestphal Balance , Instruments for Natural PhilosophyBalance de Westphal, Le Compendium
Accurate specific gravity determinations with the Westphal balance are possible only when the weight of water displaced by the plummet at 15° and the weights of the riders possess an exact multiple relationship among themselves. Deviations from this relationship can produce errors of significant magnitude.
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