Mike's Shipwrecked Diary

Production team

It's a 9-hour flight from London Heathrow to Nairobi, where we (Jonathan, me, Kathy, the two cameramen Tony and Keith, and Rob and Simon, the sound recordists) finally touch down at 7am on the 9th July 2004. We have to wait 4 hours longer than expected for our connecting flight. There's a mechanical fault with the small propellor plane that we're booked on, and we end up having to take a scheduled Kenyan Airways jet flight instead. Two hours later we're on the small island of Zanzibar, our home for the next five weeks. We're met at the airport by the rest of the Production Team. They've already been out here for two weeks - setting things up - no mean feat given that it's Africa, where even the simplest task takes an age to accomplish. They're pleased to see us, and we to see them. At last we can all set to work on a project that's already been three months in the making. We're raring to go.

Zanzibar's a beautiful place, just off the coast of Tanzania in East Africa. It's six degrees south of the Equator, tropical, and hot. Zanzibar's known as the 'Spice Island', as its main exports are spices like cloves, cinnamon and turmeric. Astonishingly, Zanzibar produces over 90% of the World's clove oil. Despite the late-afternoon heat, and the tiredness that's a travelling companion on any long journey, I'm glad to be here.

Two days rest to get over the travelling, and the filming of Rough Science 5 will be on the road. Who would have thought on Capraia, the location of the very first series of Rough Science, that we'd be making a fifth here in Africa?

Production team

Day 1

On the first day of filming it's up at 6.30am, a shower, breakfast, and a 45-minute drive (northwards along the coast) from where we're staying in Stonetown (aka Zanzibar Town; more later) to our workshop base at Chuini. My challenge for the first programme is to produce iodine from seaweed. None of us knows whether the seaweed around Zanzibar contains enough iodine to be able to extract it in sufficient quantities for our purpose - to purify the drinking water that we'll be taking with us on the boat on Day 3 of this first challenge.

For Ellen and me it's a  four hour return trip in a four-wheel drive to the east coast, where she thinks there's seaweed that will do the trick. We spend an hour or two at low tide trying to harvest enough to take back to base, where I can set to work extracting the iodine.

We're not back at Chuini till well after 2pm, and the rest of the afternoon is spent burning the seaweed to ash over a fire. To get the iodine out, I have to dissolve the ashes in water and filter off anything that doesn't dissolve. At this stage, the iodine is mostly in the form of water-soluble potassium and sodium iodides. Of course, these will be mixed with other inorganic salts that the seaweed has absorbed from the sea. By concentrating the filtrate (the solution that passes through the filter - in our case, cotton wool and muslin cloth), we'll be able to selectively remove some of the inorganic salts that we don't want (a process called fractional crystallisation), and increase our chances of extracting iodine.

We've collected two huge baskets of seaweed, and burning that much to ash takes several hours. The job's made much easier by the fact that I have a helper this afternoon; one of the Zanzibari drivers, Kitende, who's been hired to ferry us from location to location - Hisdory and Hamdani are the other two drivers. Kitende helps out by stoking the fire and starting the filtration process. By the end of a long day, we've reduced most of the seaweed to ash, dissolved the ashes in boiling water, and are well into filtering the resulting aqueous solution. It's been a tiring day working alongside a roaring fire in these temperatures. You sweat buckets. Although I've been allocated a wonderful laboratory space at Chuini, we're working outside in the heat of the sun, because of the smoke from the wood fire, and the somewhat hazardous nature of the Chemistry involved.

We still have a lot to do over the remaining two days. In fact, we effectively only have two and a bit days for this challenge as we spent a long time this morning filming the opening sequences for the first programme, when Kate (Humble) gives us our challenges. The trip to collect the seaweed ate into the day too. It's a good job that this first challenge is a light one.

It has to be said that the Production Team has done an excellent job in kitting our Chuini base out. We seem to have everything we need at the moment, and can always fall back on our reliable, local 'fixer', Eddie, for anything we might subsequently want. It's comforting to hear from the locals that you can get hold of anything on Zanzibar. Over the next few weeks, I'm sure we'll be putting their claim to the test.

Production team

Day 2

This morning, Kitende and I finish off the extraction process we started yesterday afternoon. By late morning I'm ready for the next step, playing around with some car battery acid to give us concentrated sulphuric acid. We'll need this to convert the iodides to iodine. Untreated battery acid is too dilute to do the trick; I need something a little stronger. Kitende can't be involved in this part of the challenge, as the chemical we're working with is best handled by someone who knows what they're doing (don't laugh).

It's been a fairly undemanding day, and by the end of it we have the reagents we need - a boiled down aqueous extract of the iodides and other salts from the seaweed, and some concentrated sulphuric acid.

Day 3

Iodine is a beautiful, purple solid at room temperature. Solid iodine has this unusual property that when you heat it, it sublimes (passes straight into the vapour phase; in other words, it becomes a gas). Iodine can't be liquid at ordinary temperatures and pressures. Ice, for instance, when heated, will eventually become liquid water, which on further heating becomes water vapour, or steam. With iodine you pass straight from solid to gas, and vice versa.

We can use this rather strange property (in reverse) to convert any iodine vapour that we form from the reaction of the sulfuric acid with the concentrated seaweed liquor into solid iodine. When I add the concentrated acid to the liquor, a beautiful, purple vapour forms. On hitting the cold 'finger' inside the reaction vessel, iodine does indeed solidify out. Unfortunately, our Zanzibarian seaweed contains so little iodine that we're unable to extract it in sufficient quantities to show the element's real beauty. Had we been able to generate enough iodine it would have condensed as purple, crystalline needles. The small amount of brown solid that we end up with is enough though, as we only need a very small amount to purify our boat's water supply. We're able to prove that this is iodine, by carrying out a simple starch/iodine test on some and our purified water doesn't taste that bad at all!