How to Dry Argon Gas
Scientists frequently encounter scenarios in which anhydrous gases must be used during an experiment. Chemists, for example, must carry out some reactions under conditions of very low moisture. Some instruments, such as gas chromatographs, require anhydrous "carrier" gases to function properly. Although science supply stores carry premanufactured drying tubes -- usually called "moisture traps" -- many scientists choose to build their own, either to save money or for the sake of expediency. Numerous drying agents are suitable for use with gases, including calcium chloride, magnesium sulfate and calcium sulfate. Argon gas exhibits no chemical reactivity under normal conditions, thus eliminating any concerns over chemical compatibility.
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Things You'll Need
- 100 grams of molecular sieves or other drying agent with large particle-size
- glass tube, at least 1 foot long and 0.5 inches in diameter
- 2 rubber stoppers to fit ends of glass tube
- 2 2-inch-long pieces of 0.25-inch glass tubing
- 2 pieces of 0.25-inch plastic or rubber tubing
- 2 hose clamps
- 1 0.25-inch stopper boring tool
- Glycerine
- Leather gloves
- 8 to 10 cotton balls
Instructions
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Preparation of Drying Tube
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1
Put on leather gloves and use the stopper boring tool to cut a 0.25-inch diameter hole through both rubber stoppers.
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2
Lubricate the 0.25-inch pieces of glass tubing by wetting them thoroughly with glycerine and insert them through the rubber stoppers such that less than 0.5 inches protrudes from the narrow end of the rubber stoppers.
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3
Insert three or four pieces of cotton in one end of the large glass tube, then insert one of the rubber stoppers into the end.
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4
Pour the drying agent into the open end of the glass tube and fill to about 1 inch short of the open end of the tube.
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5
Repeat step 3 for the open end of the glass tube.
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6
Attach plastic or rubber tubing to the small glass tubes protruding from the rubber stoppers, then fold the tubing over on itself to crimp the tubing and attach a hose clamp to hold the crimp in place. This prevents moist air from contacting the drying agent.
Installing the Drying Tube
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7
Remove both hose clamps so gas can flow freely through the tube.
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8
Attach one of the rubber tubing lengths to the argon source. If the argon is contained in a gas cylinder equipped with a regulator, this may require a tubing adapter for the regulator.
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9
Immerse the other end of the glass tubing in a glass of water and slowly open the argon supply valve. Bubbles should emerge from the immersed end of the tube. If it does not, the drying tube is packed too tightly or otherwise obstructed and should not be used.
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10
Attach the other piece of rubber tubing to the device being supplied with argon. The drying tube should essentially sit between the argon source and the piece of equipment where the argon is being used.
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1
Tips & Warnings
A particular drying agent, known as "indicating silica gel," will change from blue to pink when it has become saturated with water, thus giving a visual indication of when it should be "regenerated" by heating it in an oven. It can be safely mixed with most other drying agents. Drying agents without an indicator will simply require periodic regeneration at regular intervals, such as weekly or monthly.
