Preparation of 250 ml of M/20 Solution of Mohr’s Salt
Watch glass, weight box, fractional weight box, 250 ml beaker, glass rod, 250 ml measuring flask and wash bottle.
Mohr’s salt, cone. H2SO4 and distilled water.
- Weigh the clean and dry watch glass and record its weight in the note-book.
- Weigh accurately 4.9 g of Mohr’s salt crystals on the watch glass and record the weight in the note-book.
- Transfer carefully the weighed Mohr’s salt from the watch glass into a clean 250 ml beaker. Add to this beaker about 5 ml of cone, sulphuric acid to check the hydrolysis of ferrous sulphate.
- Wash the watch glass thoroughly with distilled water to transfer the sticking salt completely into the beaker. Dissolve the salt in the beaker with gentle stirring.
- Transfer the entire solution carefully into the 250 ml measuring flask through a funnel.
- Wash the beaker with distilled water and transfer the washing’s into the measuring flask.
- Add enough distilled water to the measuring flask carefully up to just below the etched mark on its neck with the help of wash bottle.
- Add the last few drops of distilled water with a pipette until the lower level of the meniscus just touches the mark on the measuring flask.
- Stopper the measuring flask and shake it gently to make the solution homogeneous (i.e., uniform throughout) and label it as M/20 Mohr’s salt solution.