How To Use Vacuum Desiccator Cabinets?

Desiccators are storage cabinets with dry atmosphere which contain desiccants in sealable enclosures in order to prevent moisture sensitive contents like cobalt, chloride paper for further use. It has great role in protecting those hygroscopic chemicals from humidity which reacts with water. 

In static desiccation system, there are various sizes that vary between an in-line cartridge sizes to a larger cabinet that may be nitrogen purged, or may contain a desiccant tray. Whenever the lids of the desiccators are opened, the contents inside are exposed to atmospheric moisture. Therefore, the chemicals like alkali metals, which react fast with atmospheric moisture, are not appropriate for storing. Instead, schlock-type apparatus or a glove box may be more suitable for such kind of storage.

In some cases, desiccators may even be used for removing moisture from an almost-dry sample. But when it is considered that desiccator cabinets alone will not be enough for the purpose, Abderhalden's drying pistol may be used in that case.

How vacuum desiccator works?

Desiccator cabinet works by preventing oxidation of MSD in the cabinet by controlling moisture. When a porous desiccant such as the silica gel is used by Dri-Box, it removes water from air space by multi layer absorption. The thin layers of the water molecule are attracted to the surface areas of the desiccant in that process.

It also works by the process of capillary condensation in which most of the smaller pores are filled with water.

The purpose of using the desiccator during the cooling of the crucible

In a desiccator, heated materials are cooled in order to prevent it from accumulating moistures while it gets cooled. The interior of the desiccator will remain dry as the desiccant is at the bottom, and the moisture in the atmosphere cannot enter the container as it is completely sealed.

Why are you to cool the crucible before it is weighed?

If you put the hot crucible for weighing its mass, the convection currents will start happening in the surrounding air around the crucible. That is why, whenever you need to weigh a crucible, you must let it cool first as the heat from the crucible warms the surrounding air and causes it to rise upward and then it cools down and falls.

The way of using desiccators in laboratory

Most of the laboratory desiccators are round in shape and made of heavy glass. It is usually placed on a removable platform so that it can be stored properly in a laboratory.  The desiccant, such as Silica Gel, fills the space under the platform. The color changing silica has a key role as an indicator whenever it would be refreshed. Whenever the indicator gel absorbs moisture it typically changes from blue to pink. The other colors may also be used here.

There may be a stopcock included for permitting the desiccator to be evacuated. These kinds of models are actually known as vacuum desiccator cabinet.

While applying the vacuum of a desiccator, it should be properly strapped in order to minimize the damage to the desiccator by a sudden implosion. Vacuum grease is applied here to achieve a good seal.