Safe Handling of a Laboratory Desiccator

Desiccator with provision for vacuum
Desiccator with provision for vacuum
Desiccator with provision for vacuum (Image Courtesy : http://www.labplastic.co.in/)

A laboratory desiccator is a round shaped closed vessel made of heavy glass which is a common laboratory glassware item and has multiple uses, such as:

  • Storage of standards under dry environment
  • Storage of materials for weighing to constant weight
  • Prolonged storage of hygroscopic materials
  • Determination of loss on drying of manufactured products such as pharmaceuticals

The base of the desiccator supports a perforated plate below which the desiccant drying agent is kept.Commonly used drying agents are anhydrous calcium chloride, drierite (calcium sulphate) and silica. Such desiccants can be regenerated by heating. A small amount of cobalt indicator compound is generally added which turns pink from blue on absorption of moisture. This lets you know when to regenerate the desiccant.

The desiccator is effective only when sealed to prevent contact of contents with outside air. Some desiccators are provided with vacuum fittings for evacuation of inside air for long-term storage of moisture sensitive materials.

Types of Desiccators

There are four types of desiccators:

Standard: which are used as desiccant cartridges and need to be changed often, depending on how often they are used. The standard laboratory desiccator requires monitoring but is quite economical.

Vacuum: The vacuum desiccator requires a pump to remove any air or moisture from the chamber. The length of the vacuum process depends on the model.

Automatic: This desiccator is fitted with electrical fans and heaters, and they are continuously used to regenerate a dry atmosphere. It requires minimal monitoring and it’s highly reliable. But, they can be costly.

Gas Purge: The drying agent used in the desiccator is nitrogen and argon. They maintain a dry atmosphere within the desiccator, at a faster rate.

Benefits of a Desiccator

This laboratory device can absorb moisture in humid conditions and keep the items dry and dust-free. They also prevent any hygroscopic materials from reacting with moisture that is caused by humid conditions.

It’s not used to dry material, but to maintain a dry atmosphere and keep the material dry. Some laboratory desiccators are used for cooling a heated object or material.

In any regulated environment, such as a laboratory, there is a need to control the environment because it determines the completion of various tasks. Many factors cause a hindrance like fluctuating temperatures, dust particles, humidity, and so on; hence, these elements have to be controlled and regulated.

Listed below are some of the top benefits of each desiccator:

Standard Desiccator: This unit is operated and monitored manually. It will take in the moisture, and once saturated, you will have to replace or heat it to regenerate the desiccant. These units provide flexibility, are affordable, and quite convenient.

Automatic Desiccator: These require minimal monitoring and make use of heaters/electric fans to prevent saturation. The humidity is maintained at a constant low and the units are programmable; they are also set to operate on a preset schedule.

They provide control over humidity and use silica gel beads that last for a long time, this also reduces the need to replace the desiccation material, constantly.

Gas Purge Desiccator: If you want fast removal of humidity, the best bet is to opt for a gas purge desiccator. They use a slow and steady flow of inert gas to extract moisture. The gas used is usually dry nitrogen, which is available easily. These units create a dust-free environment and are great for clean rooms.

Vacuum Desiccator: If you are stuck in a situation where you need to remove air and humidity, go for a vacuum desiccator. These units remove air and moisture with a vacuum pump. They are great at collecting dust and can be used as standard desiccators as well.

Tips to Consider before Purchasing a Desiccator

Controlling the Dry Environment

The main purpose of a desiccator is to keep the components dry and not let any moisture seep in. Hence, before you buy a laboratory desiccator ensure that you check it thoroughly and gauge its moisture-prevention capability, as well.

Humidity Control Length

Some desiccators tend to offer humidity control features, but it’s only there for a limited period when compared to advanced versions. The advanced versions include humidity control benefits at any time.

Depending on the function of the desiccator, and whether you want to use it temporarily or permanently, you should purchase it accordingly.

Price

The price of a desiccator depends on their type, size, style, automation. If the apparatus is sophisticated, it will be costly.

Portability

Some experiments or labs need to move the desiccator from one location to another. Therefore, mobility becomes an important factor in the desiccator selection.

Interval Monitoring

As mentioned before, standard desiccators will need to be monitored frequently and automated ones require minimal monitoring. Therefore, you need to consider if you have the bandwidth to monitor the desiccator for a long time or not; it’s your decision if you want to do it manually or automatically.

Drying Speed

Some laboratory desiccators will take more time to dry the components than others. Hence, you need to see the speed at which you want the drying to occur because it will help you determine the selection criteria.

The Reputation of the Supplier

It’s advisable to purchase desiccators from a trusted and reputed supplier. Go for suppliers that will provide you with desiccators that have minimal risks, defects, or damages.

Safe Handling and Use of a Desiccator

The desiccator is often taken for granted and precautions in its handling get often ignored. However, bear in mind that accidents can occur if sufficient care is not exercised in handling and use of desiccators.

The cover of the desiccator is usually sealed to its body with a thin layer of silicone grease. This forms an airtight seal and requires precaution in opening the cover and putting it back.

  • Slide cover horizontally with a gentle force until it starts moving. Grasp the knob with one hand and with the other hold the base and apply more force to take it off completely
  • Do not get tempted to lift the desiccator by lifting the top knob. Always lift with both hands holding the bottom and the cover.
  • To close place lid gently on top and close slowly by applying a mild force till it closes. Rotate lid gently in both directions to ensure an airtight seal.
  • Ensure that the rim does not run out of grease but at same time do not use an excessive amount of grease. A thin uniform film is usually sufficient.
  • Keep the lid upside down on removal but away from the workbench edge to prevent rollover
  • Place a hot substance carefully inside after removal from the hot air oven. Keep the crucible with the lift ajar for a couple of minutes and then close the lid by sliding it to expel hot air so that the lid does not get blown out due to expansion of hot air and also prevent vacuum formation later which can make opening difficult.

Opening a Vacuum-Sealed Desiccator

When applying a vacuum take care not to exceed the prescribed limit as it can risk an implosion. Gradually open stop- cock on top to release the vacuum inside at time of opening. Try sliding the lid. If there is difficulty in sliding make use of a thin spatula carefully to create a rift between the lid and the body. On hearing a hissing sound of vacuum release slide the top cover by holding the bottom firmly with the other hand.

A desiccator can be used routinely for storage of moisture sensitive compounds, standards and for applications requiring weighing to constant weight. However, storage of materials that are highly reactive with water such as sodium metal is not recommended as on coming in contact with humid air on opening it can lead to violent reaction.

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