July 23, 2005
Photochlorination of Tetrachloroethylene (Cl2C=CCl2)
Above is the setup I used for my experiment. Starting from the left, a two neck flask filled with 250 grams of calcium hypochlorite with a stirring bar. In the top neck is a separatory funnel containing concentrated sulfuric acid. The neck to the right was a thermometer adaptor hooked to a piece of glass tubing leading to a gas wash bottle filled with sulfuric acid to dry the formed chlorine. From here the formed chlorine leads to a one neck 500 ml flask containing 100 ml tetrachloroethylene. This flask is placed into a inverted wooden bowl fitted with 70 UV LED lights. The attachment at the top is just a gas bubbler. The exit gasses are lead to another separatory funnel. This one inverted into a concentrated sodium hydroxide solution to neutralize any Cl2 that made it that far. The advantage of a separatory funnel being a stopcock to stop suck back if necessary (which it was) and it took a lot of liquid being sucked up to fill it.
Now, onto the reaction. Chlorine was made by adding the sulfuric acid drop wise to the hypochlorite. The stir bar which was initially going well in the powdery hypochlorite stopped spinning in short order from the reaction gumming it up, for the remainder of the experiment it simply vibrated, should have made a slurry. Anyway, the chlorine passed along and into the UV chamber and it dissolved well and reacted. This went on for 6 hours. The problem being the chlorine generator was highly unreliable in terms of the rate of reaction. This actually caused an entry into my mistakes page. Never the less, a chlorination was happening well in the photo chlorination chamber. When the chamber was removed the LED lights were cool to the touch. However the flask was hot, hot enough to volatize the chlorinated products which should have had boiling points from 60 - 120 °C. I will fraction this product at a later date to better determine the amounts of product obtained.
July 30, 2005
Preparation of Formic Acid (HCOOH)
Formic acid, simple enough eh? I attempted the time tested reaction between dried glycerin and oxalic acid dihydrate to produce this useful chemical. 40 grams of the dihydrate were mixed with nearly 100 ml of glycerin which had been heated to 160 °C slowly and held there for five minutes while it smoked and bubbled. This mixture which quickly became homogenous owing to the oxalic acid dissolving was setup for distillation in an oil bath (vegetable oil) with magnetic stirring, the second neck of the flask contained a stopper so I could add oxalic acid through the neck as the reaction progressed, and the temperature of the reaction was read by the temperature of the oil in which a thermometer was immersed.
Now, at the very beginning I got some distillate below 100 °C but it started climbing. I got crap for distillate in the course of two hours (<10 ml) so I added some more oxalic acid and heated up the reaction mixture more. I also wrapped the reaction apparatus in insulation to allow it to distill easier. Too bad the worst effect I could see the increased heat causing to the distillation was some glycerin being carried over. However I later found that if the reaction mixture becomes too high all kinds of side reactions take place. At the end I was holding the reaction mixture at about 165 °C but was still hardly getting any distillate. When I was done and gave up after spilling oil on my hotplate I had about 15 ml distillate that had no strange smell and showed no action on aluminum. However the reaction flask was giving off terrible burning fumes that were similar to acetic acid, likely the formic acid I was shooting for. Too bad I don't think much of it carried over. I did find one interesting thing though, all the side reactions turned by reaction mixture from clear to a pink/purple color that looked pretty neat. Next time I will be more careful with temperature control or will attempt to find a better was to formic acid.