Preparation of mixed polysulphanes

Polysulphanes are interesting compounds. At room temperature they exist as toxic yellow liquids. The three stable polysulphanes are disulphane, trisulphane and pentasulphane. They are all very sensitive to alkalies so the glassware used to make these compounds must be washed with acid to remove trace amounts of alkali. They have few applications and uses.

I decided to try making disulphane. The reaction produces all three polysulphanes. In a future post I will perform a distillation to isolate disulphane.

The first step is to prepare a solution of sodium polysulphides.

To a 500ml beaker, I poured a solution containing 17g of sodium hydroxide and 150ml of water. I added in 20g of sulphur and began boiling the mixture. The sulphur gradually dissolved and the mixture turned a beautiful dark red colour. After all the sulphur had dissolved, 120ml of dark red liquid were left. This is the polysulphide solution.

Next the sodium polysulphides must be acidified to yield the polysulphanes. All equipment used in this procedure was washed with 5% acetic acid to prevent decomposition of the polysulphanes.

In a 500ml beaker, I chilled down 20ml of the solution prepared in step one to 0 C. The reaction is best performed at -15 C but 0 C was as cold as I could get. After this temperature had been reached, I added the solution to 60ml of 33% hydrochloric acid (also chilled to 0 C). If the starting solution and the acid aren't chilled, only hydrogen sulphide and sulphur will be formed. Anyway, after the addition, a bit of hydrogen sulphide was produced along with some solid sulphur. I stirred the mixture then let it settle. After this, the polysulphanes could be seen as a vivid yellow liquid at the bottom of the container separate from the surrounding liquid. 

The product was collected with a syringe and placed in an acid-washed vial. I got 0.7ml of mixed polysulphanes.

S8 + 12 NaOH = 4 Na2S + 2 Na2S2O3 + 6 H2O  /  S8 + 4 Na2S = 4 Na2S3

S8 + 8 Na2S = 8 Na2S2  /  S8 + 2 Na2S = 2 Na2S5  /  Na2Sx + 2 HCl = H2Sx + 2 NaCl

Nitrocellulose

Cellulose hexanitrate, commonly called nitrocellulose, is a very interesting explosive. When ignited unconfined, it bursts into a large ball of flame. This happens so fast that it's actually safe to ignite it on your hand. When the nitrocellulose is tightly confined it detonates, resulting in a violent explosion. Nitrocellulose was first prepared by Henri Braconnot in 1832. The synthesis of nitrocellulose is a chemistry classic.

Nitrocellulose is usually prepared from sulphuric and nitric acids, however I substituted the nitric acid with potassium nitrate.

To a beaker in an ice bath, I added 50ml of 98% sulphuric acid. I let the acid cool for 5 minutes, then over the course of 30 minutes added 25g of potassium nitrate in portions. This forms the required nitric acid in situ. After the nitrate addition, using a glass stir rod, I pushed pieces of cotton wool in until no more could be covered by the mixture. I left this overnight. The cellulose in the cotton reacts with the acids to form nitrocellulose. Anyway the next morning, I removed the nitrocellulose and added it to a bucket of water. I left it in the bucket for about 15 minutes to soak, then swirled it around in the water until it uncaked and started looking like cotton wool again.

I washed the nitrocellulose with 500ml of saturated sodium bicarbonate solution to remove traces of sulphuric/nitric acid. Then I washed it with water again to remove the sodium salts from the product.
I then dried it. I couldn't weigh the nitrocellulose as the pieces were too big to fit on my scales.

Left = dry nitrocellulose  /  Right = nitrocellulose deflagration unconfined
H2SO4 + KNO3 ==> HNO3 + KHSO4  /  HNO3 + 2 H2SO4 ==> 2 HSO4 (-) + NO2 (+) + H3O (+)

Synthesis of boron

Boron is an interesting element used in high strength fibers. It burns with a nice green flame. I plan to use it to make boron tribromide. I tried making some boron from boric acid.

The first step is to convert the boric acid to boron trioxide.

To a metal can, I added 15g of boric acid. Then I heated the can on a medium heat. After 5 minutes the boric acid had began to melt and decompose. Ten minutes after this, the mixture had turned to a bubbling sticky mess. I kept the heat on for another 10 minutes. After this, a sticky glassy mass remained in the can. Upon cooling, it solidified into rock-hard crystals of boron trioxide. The boron trioxide was scraped off the can and collected.

The final step is to reduce the boron trioxide to elemental boron.

I ground up the boron trioxide crystals from step one into a fine powder. This was very difficult and took several hours. Then I added a roughly equal amount of magnesium powder and cuttings to the boron trioxide. I blasted the mix with a butane torch until all the mixture had turned black. I was expecting the mixture to act like a thermite and not need to be torched. I think the reason this didn't happen was because half my magnesium was not powdered. Anyway, after this I added the black residue to a beaker and added about 50ml of water. I then slowly added 12M hydrochloric acid until the acid stopped affecting the mixture. The mixture fizzed and lots of gas was produced during the addition.

I noticed a disgusting smell. This is most likely borane gas. Once the mixture had stopped bubbling, I added 400ml of water to dissolve any residual boron trioxide. Then I filtered the mixture to collect the boron product. I got 0.06g of boron as a black powder, which is a miserable 1.2% yield.

I blame the extremely low yield on the thermite not working. The butane torch probably didn't do a very good job.

2 B(OH)3 ==> B2O3 + 3 H2O  /  B2O3 + 3 Mg ==> 3 MgO + 2 B

Acetone semicarbazone

Acetone semicarbazone is an organic compound derived from semicarbazide. It's got quite an interesting structure. I plan to use acetone semicarbazone to make semicarbazide.

I made acetone semicarbazide using a synthesis from www.prepchem.com which I modified slightly.

To a 250ml conical flask, I added 2.29g of hydrazine sulphate, 2g of sodium carbonate and 2ml of water.

After stirring, I poured in a solution of 1.14g of sodium cyanate in 25ml water along with 2ml of acetone. I stirred the mixture well for 10 minutes then left it to stand for 24 hours. After this, I filtered the mixture, collecting the filtrate. I evaporated the filtrate down to dryness, then to it I added 50ml of ethanol. The original procedure called to use a soxhelt extractor but I don't have this. Anyway I stirred the mixture so the ethanol could dissolve as much product as possible. Then I filtered the mixture again collecting the ethanolic filtrate.

I dried the filtrate in a crystallizing dish and was left with a pathetic amount of acetone semicarbazone. The amount was so small that I didn't bother weighing it. So I'm not sure what the yield was.

I think a larger quantity could have been obtained if I had used a soxhelt extractor or a least used hot ethanol. Warming the mixture before the cyanate addition would probably have helped as well.

see here for how this reaction works

Thorium dioxide from electrodes

Thorium dioxide (ThO2) also known as thoria is a weakly radioactive compound used in some welding electrodes. Thorium gives off alpha radiation which can't penetrate paper and is very short ranged, so it's only dangerous if inhaled or consumed. Thorium dioxide used to be used in gas mantles but this was stopped due to concerns about the radiation. I plan to use thorium dioxide to make Thorium metal and generally explore thorium chemistry.

Thorium dioxide can be extracted from thoriated tungsten electrodes used in welding.
These are usually 2-4% thorium dioxide.

Two years ago I brought 4 thoriated tungsten electrodes. I added them to a container of 3% hydrogen peroxide and left them there until the electrodes had corroded away.  After this there were lots of yellow crystals were left. I collected the crystals and placed them in a vial.

Yesterday I decided to purify the thorium dioxide. I realized my sample was probably a mix of thorium dioxide and tungstic acid. So I added the the yellow crystals to 5ml of saturated sodium carbonate solution and heated strongly for a few seconds. The yellow tungstic acid began to react away and a white powder (presumably thorium dioxide) remained. Once this had stopped, I filtered the mixture to collect the white thorium dioxide. Then I added the thorium dioxide to another 5ml of sat sodium carbonate solution to make sure all the tungstic acid had gone. After this, I filtered off the thorium dioxide and dried it. I got 0.8g of slightly yellow thorium dioxide.

 

 left = the thoriated electrodes (image from www.ecvv.com)  /  Right = thorium dioxide

H2WO4 + Na2CO3 ==> Na2WO4 + H2O + CO2

Ethyl bromide

Ethyl bromide, also called bromoethane, is a volatile organic used as a ethylating agent. It's a very useful reagent to have. I plan to use ethyl bromide to make tert-pentanol and ethylamine. Ethyl bromide must be handled with care as it's a suspected carcinogen.

Ethyl bromide is easily prepared from ethanol, sulphuric acid and sodium bromide. I chose to use this method.

To a 1000ml round-bottom flask I added 74ml of ethanol and 50ml of water. I placed the flask of ethanol and water in an ice bath and slowly over the course of 30 minutes added 80ml of 98% sulphuric acid. I took care to ensure the mixture didn't heat up too much during the addition. After this, I added 70g of sodium bromide and set up for simple distillation. In the receiving flask I placed 25ml of water. I began distilling the mixture at a medium heat. Ethyl bromide began distilling over. When no more ethyl bromide passed over, the distillation was stopped.

The ethyl bromide had formed a layer underneath the water in the receiving flask. The ethyl bromide layer was collected with a syringe and washed with sodium bicarbonate solution. Then it was loaded into a watertight bottle and 25ml of sodium bicarbonate solution was added on top of the product to prevent it from evaporating. The lid was sealed with duct tape.
I got about 25ml of ethyl bromide which is roughly a 33.5% yield.

C2H5OH + H2SO4 ==> C2H5HSO4 + H2O  /  2 NaBr + H2SO4 ==> Na2SO4 + 2 HBr

C2H5HSO4 + HBr ==> C2H5Br + H2SO4