Make: Projects – Pneumatic trough, part II
November 20th, 2009 | 
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Last week I wrote about how to construct a simple sheet metal "bridge," which, in combination with an ice cube bucket and an olive jar, makes an effective pneumatic trough for collecting gas samples over water. This week I'm going to show you how to use this apparatus to generate and collect pure oxygen, and how to use that oxygen to observe the brilliant blue flame of sulfur oxidation.
CAUTIONAs a general rule, flammable greases like petroleum jelly should not be exposed to pure oxygen. There is no appreciable danger in this experiment, which involves only a small volume of oxygen at atmospheric pressure in a container with a free lid, but if you are working with larger volumes of oxygen, oxygen under higher pressure (as in a cylinder), or (most emphatically) liquid oxygen, do not use grease or other readily oxidizable materials in constructing apparatus.
Tools:
- Pneumatic trough apparatus from part I
- Small piece of plate glass (I used the mirror from a makeup compact)
- Lighter
- Twisted wire sample loop
- 250 mL Erlenmeyer flask (I got mine from The Maker Shed)
- #7 two-hole rubber stopper to fit Erlenmeyer (mine came from this assortment)
- Two 80 mm lengths of 5 mm glass tubing to fit stopper (such as this)
- Approximately 18" length of 5/16" OD x 3/16" ID PVC tubing to fit glass tubing (common hardware store item)
Materials:
- Water to fill bucket
- Elemental sulfur powder (also called "Flowers of Sulfur," available at some drugstores and here.)
- 3% hydrogen peroxide (common drugstore item)
- Manganese dioxide (can be recovered from an alkaline dry-cell battery or purchased here)
- Petroleum jelly (drugstore)
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