|MadSci Network: Earth Sciences|
There are three “standard” laboratory volcanoes. The first two listed below are very dangerous and should only be performed by a skilled chemist with appropriate safety measures. I very strongly recommend the third measure listed below. It is less spectacular but is usually adequate AND much safer for the operator and spectators Permanganate Volcano The permanganate volcano is based on the reaction between potassium permanganate (KMnO4 ) and concentrated sulfuric acid which gives a dark green oil (Mn2O7) that undergoes rapid decomposition in the presence of moist air to form MnO2 and oxygen. 2 MnO4-(aq) + 2 H+(aq) --> Mn2O7(l) 2 Mn2O7(l) -->4 MnO2(s) + 3 O2(g) There have been several serious accidents with this demonstration. In one case, during a practice session prior to class, enough acid was added to cover the permanganate completely. When the demonstrator walked to the blackboard, the mixture detonated, shattering two panels of the chalkboard and spraying reagents over a distance of 40 feet. The demonstrator was not injured. In a second case, however, 15 sixth-grade students were injured, two seriously, when this demonstration exploded. Ammonium Dichromate Volcano An exciting demonstration volcano can be made with a bit of ammonium dichromate. This is a fun science demonstration that takes almost no time at all to prepare. Place a small quantity (12 to 15 grams, or half an ounce) of Ammonium Dichromate powder on a clay tile. Form the powder into a cone shape. Dim the room lights, and light the top of the cone with a high heat source such as a propane torch. The ammonium dichromate will burn fiercely while producing large volumes of a grayish green ash. Small orange sparks will shoot upward a couple of inches. This reaction can be incorporated into your papier-mache volcano model like this: At the top of your model, insert either a 30 ml crucible, a jar lid, or some other flame-resistant container. Coat your volcano model with a plaster slurry to fireproof it, especially near the top of the cone. Place the ammonium dichromate in the fire resistant cup at the top of the volcano, and light it. While this demonstration has been used for many years in education, some chromium compounds have been found to be carcinogenic. No one can eliminate the possibility of contracting cancer. Wash your hands after performing the experiment, and use adequate ventilation. Sodium Bicarbonate Volcano - RECOMMENDED The volcano shape itself is free formed on a sturdy sheet of plywood. Many methods can be used, including built up plaster, wallpaper paste, play dough (salt dough) and paper-mache. It is built around an empty, open bottle, which will form the opening at the top from where the lava emerges. Work with it until you get a shape you like. It is good to leave some cracks and furrows for your lava to flow through. Decorate as you see fit. Once everything is dry and firmly set, it is a good idea to spray it with a clear finishing spray to seal it. Put a tablespoon (15 ml) of baking soda, a tablespoon (15 ml) of liquid dish soap, and some red (and possibly some yellow) food coloring in the jar. Add 1/4 cup (60ml) or so of vinegar. It will make a mess, so do it where this doesn't matter so much (outdoors). If the "lava" seems a little thick, next time try adding some water to the mix before adding the vinegar.
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