Vacuum Desiccators
Vacuum Desiccators: How They Differ from Plain Desiccators and How to Use Them
A desiccator keeps samples dry during storage and cooling. A vacuum desiccator adds a stopcock and stronger construction so the internal pressure can be lowered - drying becomes much faster and more complete, but there are rules to follow.
- Vacuum stopcockPTFE, adjustable
- Borosilicate glassthermal shock resistant
- Porcelain plateperforated sample support
- Vacuum pumps availableoil-free diaphragm
Plain versus vacuum desiccator
Plain desiccator (no stopcock)
- Relies on the desiccant alone to absorb moisture inside a closed vessel.
- Adequate for cooling crucibles after ignition and storing dry samples.
- Cheaper and needs no pump.
Vacuum desiccator (with stopcock)
- The stopcock lets the pressure be lowered with a vacuum pump, so moisture is drawn out rather than merely absorbed.
- Drying is far faster and can reach lower moisture content at room temperature.
- Must use glass designed for vacuum and be opened carefully.
Using a vacuum desiccator correctly
- Prepare the desiccantPlace silica gel or another desiccant at the bottom, then fit the perforated plate as sample support. Saturated silica gel must be regenerated in an oven.
- Grease the jointApply a thin, even film of vacuum grease to the ground joint so the lid seals and does not seize permanently.
- Evacuate slowlyOpen the stopcock to the pump and lower the pressure gradually. Evacuating too quickly can scatter fine powders and make solutions boil over.
- Close the stopcock, remove the pumpOnce the pressure is reached, close the stopcock first, then switch off and disconnect the pump so there is no backflow.
- Vent slowly before openingNever try to lift the lid while under vacuum. Admit air slowly through the stopcock until pressure equalises, then slide the lid sideways.
Desiccators and accessories
| Model | Best for | Price | Purchase |
|---|---|---|---|
| Normax PA 49 060 glass desiccator with stopcock | With stopcock, usable under light vacuum | Rp 2.821.000 | Buy online |
| Normax PA 49 065 desiccator with rotating sleeve | The rotating sleeve eases pressure control when opening | Rp 3.195.000 | Buy online |
| Normax PA 49 061 glass desiccator without stopcock | Storage and cooling without vacuum | Rp 1.854.000 | Buy online |
| Normax PA 49 064 02 porcelain desiccator plate | Perforated sample support | Rp 752.000 | Buy online |
| Normax PA 49 063 19 replacement desiccator lid | A spare when the lid breaks | Rp 1.142.000 | Buy online |
| Duran NOVUS vacuum desiccator 300 mm, PTFE stopcock + porcelain plate | 300 mm borosilicate with PTFE spindle stopcock; already delivered | on request | Request quote |
| Infitek VACP-D31 diaphragm vacuum pump | Oil-free, for evacuating the desiccator | Rp 11.981.430 | Buy online |
| Joan Lab VP-6L mini vacuum pump | A compact, economical option | Rp 3.030.000 | Buy online |
Store catalogue prices before 11% VAT and shipping; subject to change. Stock and delivery time are confirmed in the quotation.
Frequently asked questions
What is a desiccator for?
Storing samples, crucibles and hygroscopic materials so they do not take up moisture from the air, and cooling crucibles after ignition before weighing. An illustrated explanation is at desiccator uses.
Which desiccant is used in a desiccator?
Silica gel is the most common because it is cheap, safe and regenerable in an oven. For deeper drying, stronger desiccants are used, but they are riskier to handle.
Why is the desiccator lid hard to open?
Usually because a vacuum remains inside, or the vacuum grease has dried and stuck. Admit air through the stopcock until pressure equalises, then slide the lid sideways - do not lift or pry it.
Is a glass desiccator safe under full vacuum?
Only use a desiccator rated for vacuum, and consider a guard or shield. Glass that is scratched or has been knocked should never be evacuated.
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