Bromine is a dark red liquid with a boiling point of 59C named after its strong and irritating stench (bromos in Greek). It is the only element other than mercury to be a liquid at room temperature. It is a relatively important reagent in organic chemistry, which is why I must make it. It also just looks damn cool!
Bromine was first identified in seaweed ashes and today it's produced from seawater. In the lab, it can be synthesized in several ways from a salt of bromine, most commonly sodium bromide, which is used extensively as a brominating agent for sterilizing swimming pools. Bubbling chlorine into a solution of sodium bromide displaces pure bromine.
NaBr + Cl2 --> NaCl + Br2
It can also be produced by reacting sodium bromide with concentrated sulfuric acid and manganese dioxide. The manganese dioxide serves as an oxidizer and without it, the bromide ion would only partially oxidize and you would end up with a mixture of bromine and hydrobromic acid. Other oxidizers as varied as hydrogen peroxide, nitric acid, and potassium chlorate can be used instead.
NaBr + MnO2 + 3H2SO4 --> Br2 + 2NaHSO4 + MnSO4 + 2H2O
Finally, direct electrolysis of a sodium bromide solution with graphite electrodes also yields bromine, but this is probably the most inefficient route for a home experimenter. As you can see, producing bromine from sodium bromide gives you lots of options and is quite simple. Unfortunately, I cannot find sodium bromide in any of the stores that are in my area even though Home Depot and similar hardware stores are supposed to carry it!
This presents me with a difficult challenge, synthesizing bromine from BCDMH (1-Bromo-3-Chloro-5,5-Dimethylhydantoin), the only compound with bromine that I can find around. BCDMH is also used in water sterilization as it is both a source bromine and chlorine. Very little information is available about the properties of BCDMH aside from its MSDS. Wikipedia has an article about it, but that was written by me. This places my work with BCDMH in a very unique position- serious experimentation without the aid of textbooks or the past experiences of others! Here are some properties of BCDMH that I have gleaned through cautious microscale testing.
It was the last discovery which was exciting because it offered a theoretical path to bromine synthesis. I knew that sulfuric acid reacts with hypohalous acids to give the free halogen so I figured that adding concentrated sulfuric acid to a solution of boiled BCDMH would yield bromine and chlorine. When I dropped in some sulfuric acid, the solution immediately turned from marigold to orange. Interestingly, no gas was formed. My hypothesis is that any chlorine that is produced quickly displaces the hypobromous acid and yields additional bromine. Distillation of the solution resulted in low quantities of what appeared to be bromine. Since BCDMH is a large molecule, the optimum yields of bromine are low, something on the order of 0.1mL of bromine per gram of BCDMH.
I dissolved 20g of BCDMH (one crushed tablet) in about 200 mL boiling water. Most of the BCDMH seemed not to react. It just floated and frothed up to the top of the container. The solution, however, turned a deep yellow golden color and smelled very much like bleach. I skimmed off the froth with a spoon and decanted the liquid from the unreacted solid at the bottom of the container. I then added about 15 mL 50% sulfuric acid to the solution while it was still hot and the solution immediately turned orange-red. A liquid distilled off at around 60C. I cooled my receiving container in a salt-ice bath (which had an initial temperature of -20C), but it seemed as if a lot of gas was escaping (although a substantial volume of this may have been chlorine also produced by the reaction). When I disassembled my apparatus, the flask fumed profusely but I saw a red solid stuck to the bottom of the container. I scraped this off and tried my best to pour it in a container, but it evaporated quickly. The inside of my PVC distillation set up is now stained a bright red.
I got better yields of bromine this time using 20g of BCDMH again. I reacted it with 125 mL boiling water until it turned yellow and then I decanted the solution and redissolved the unreacted solid with another 125 mL water. I added 20 mL of slightly diluted sulfuric acid to this mixture. I did not bother to filter out some of the unreacted solid when distilling. The solution turned red upon adding the acid and distillate came over at 60C. I used a salt-ice bath to cool the receiving container, but this time I used a smaller, narrower, receiving container in an effort to prevent less of the bromine from vaporizing. I got a bit of red solid bromine stuck to the bottom of the container. I put the lid on this container and it quickly turned to a liquid and almost immediately vaporized into orange gas. After a couple of hours, I noticed that the color of the gas had become lighter. The gas had eaten away at part of the metal cap of the container.
