hydrometer in action

Simple device, just a soda straw sealed at both ends with a little hot-melt glue. Inside is a small quantity of zinc powder, just enough to make it float well.

Calibration (if you can call it that) was performed with tap water for the low mark and saturated (4.6 M) KCl solution for the high mark.

Alcohol could be used to make a lower mark if desired. Acetone or other solvents will probably dissolve the straw, best to use glass if you want to use them.

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