Titanium Thermite & Calcium Sulfate

Titanium metal from a thermite reaction has been one of my goals for a long time. I needed it for my element collection, and this thermite is particularly interesting because of the surprising chemicals it uses. The formulation I am using was developed by a fellow blogger and colleague on the Science Madness forum, Gert Meyers. His blog post on the subject can be found here. The following will talk about my efforts to obtain good quality titanium metal from the thermite reaction he lays out. This is a re-post of the info I shared on Science Madness, including many pictures and 3 unlisted Youtube videos never before seen by the general public!

Experiment: Vanadium Pentoxide Thermite

Here's a quick one. This thermite was a 2.02:1 mix of V2O5:Al powder. Vanadium pentoxide is a (fairly toxic) orange powder, and it made a sandy colored thermite mix. It reacts via the equation

10Al + 3V2O5 -> 5Al2O3 + 6V

I was only able to get one good picture of the actual reaction because it happens so fast - its more like a small explosion! It produced some very bright white sparks, a color that the camera didn't capture too well. I thought it was going to start a brush fire afterward, as you can see in the last two photos by all the fire! I was able to find some small pieces of vanadium in the aftermath - a lot of which was lying in the sand nearby. Some pieces had some tarnish on them, giving them a neat iridescent purpleish shine.

Experiment: Tin Oxide Thermite

Another thermite composition - 4.19:1 SnO2:Al by weight, with about 25g total thermite. I already had tin samples for my collection, but every thermite produces a different reaction so I wanted to try it out. I wasn't disappointed. This one produced a lot of smoke and some bright sparks, following the reaction
4Al + 3SnO2 -> 2Al2O3 + 3Sn
I recovered a lump of tin caked in alumina slag that I could not easily remove since tin is so soft. I melted the piece in a crucible and was able to pour off some (relatively) pure tin that was nice and shiny. As you can see in the last picture I recovered almost 4g of tin, which was about a 20% yield.

Experiment: Silicon Dioxide Thermite

This old post serves as the Video Companion to  this video. This reaction was done some time before the video was shot, so some conditions here were a bit different (e.g. the ignition method).

This one was one of my favorite experiments to date. The silicon dioxide I used was common beach sand. I picked it up off the ground from Panama City Beach, ground it down to a finer powder in a mortar and pestile, and mixed it into thermite. This composition is extremely hard to ignite, so I added sulfur as well. This sets up a helper reaction between sulfur and aluminum that burns hot enough to sustain the rest of the thermite. The ratio I used was 9:12:10 SiO2:S:Al. This experiment was done when I was trying out different ignition methods, so here I used "thermite ignition mixture" from www.unitednuclear.com (my favorite science supplier), which was ignited with an M-80 fuse.

Experiment: Black Iron Oxide Thermite

Thermite is most commonly made with red iron oxide (hematite, or common rust), but I went with black iron oxide (magnetite) because it should yield more metal per reaction. The ratio for this is 3.22:1 Fe3O4:Al by weight.

Full reaction: 8Al + 3Fe3O4 -> 9Fe + 4Al2O3

Experiment: Manganese Dioxide Thermite

This old post serves as the Video Companion to  this video.

For this experiment, I used manganese dioxide and a much finer aluminum powder than in my other thermites, at a ratio of 2.42:1 MnO2:Al by weight (40g total). I've done this reaction before (but forgot to photograph it), and using my normal aluminum it produced a reaction similar to the iron thermite. It was a little brighter and produced more sparks. With the finer powder, things went a little differently. The small flower pot erupted in a pillar of flame about 6 feet high, with the sound of a rocket engine and heat that was felt a good 15 feet away. This is a great demonstration of the importance of particle size in thermite and most other reactions. I plan on posting a direct comparison, complete with pictures, sometime in the future.

Background: Thermite

One of the first experiments I did at my home lab, and the type I've done most often, is the thermite reaction. This is the exothermic reaction between a powdered metal oxide and a pure metal, most commonly between iron oxide and aluminum. The strength of the reaction can be determined by how far apart the two metals are in the Activity Series. For example, a copper oxide thermite should be more violent than a chromium oxide one since copper is farther from aluminum on the series than chromium (and it is, by a lot). Thermite involves a single-replacement reaction, where the more reactive aluminum replaces the other metal in its oxide, resulting in alumina (aluminum oxide) and the pure metal. The reaction is hot enough to occur in the liquid stage, so the products are generally in one solid lump after cooling. Thermite is used in some welding applications, and was used in special grenades in the military.