Desiccator (Melissa Savage)

AuthorMelissa Savage GHCHS

Principles

A common use for desiccators is to protect chemicals which are hygroscopic or which react with water from humidity.

Materials needed

Procedure

Goggles, porcelain evaporating dish, watch glass, scoopula,

analytic balance, hot plate, tongs vacuum dessicator, vacuum

pump

Purpose:

The desiccator is used to store dried samples in a dry atmosphere. It should not be used to dry an object, but to maintain an already dried object indefinitely in a dry condition.

Usage:

To open - slide lid horizontally across the top to one side until it comes off. Use one hand to hold the bottom of the desiccator while using the other hand to grasp the knob.
To close - place lid partly on the top and slide across until desiccator is completely closed and then rotate lid gently in both directions.
Do not attempt to lift lid off vertically.
Make sure the lid has enough grease around the ground glass rim - if necessary, spread Vaseline uniformly on the rim. When the lid is properly seated, the greased rim will appear as shown in the above image.
If the desiccant appears wet or clumpy, it probably needs to be replaced with new dessicant. It is helpful to have a small amount of indicating desiccant present. When the color changes to pink, the desiccant should be replaced.
Desiccants should be handled in the hood and added carefully, wearing goggles and lab coat. Desiccant should not coat the sides or plate of the desiccator.

Explanation

A desiccator or desiccant container is a chamber that removes water from chemicals or items. It is extremely easy to make a desiccator yourself using materials you probably have on hand.

Have you ever wondered why so many products come with little packets that say 'Do Not Eat'? The packets contains silica gel beads, which absorb water vapor and keep the product dry, which is an easy way of preventing mold and mildew from taking their toll. Other items would absorb water unevenly (e.g., parts of a wooden musical instrument), causing them to warp. You can use the silica packets or another dessicant to keep special items dry or to keep water from hydrating chemicals. All you need is a hygroscopic (water-absorbing) chemical and a way to seal your container.

Questions

1. What is the purpose of the vacuum dessicator? Why is the air pumped out?

2. How would your results be altered if a sample was cooled in an open environment?