Unit 2. Water

Script 3. Obesity

Drink till you drop

A magic elixir is shown to promote weight loss.

Consume more water and you will become much healthier, goes an old wives’ tale. Drink a glass of water before meals and you will eat less, goes another. Such prescriptions seem sensible, but they have little rigorous science to back them up.

Until now, that is. A team led by Brenda Davy of Virginia Tech has run the first randomised controlled trial studying the link between water consumption and weight loss. A report on the 12-week trial, published earlier this year, suggested that drinking water before meals does lead to weight loss. At a meeting of the American Chemical Society in Boston this week, Dr Davy unveiled the results of a year-long follow-up study that confirms and expands that finding.

The researchers divided 48 inactive Americans, aged 55 to 75, into two groups. Members of one were told to drink half a litre of water (a bit more than an American pint) shortly before each of three daily meals. The others were given no instructions on what to drink. Before the trial, all participants had been consuming between 1,800 and 2,200 calories a day. When it began, the women’s daily rations were slashed to 1,200 calories, while the men were allowed 1,500. After three months the group that drank water before meals had lost about 7 kg (15,5 lb) each, whereas those in the thirsty group lost only 5 kg.

Dr Davy confidently bats away some obvious doubts about the results. There is no selection bias, she observes, since this is a randomised trial. It is possible that the water displaced sugary drinks in the hydrated group, but this does not explain the weight loss because the calories associated with any fizzy drinks consumed by the other group had to fall within the daily limits.

Moreover, the effect seems to be long-lasting. In the subsequent 12 months the participants have been allowed to eat and drink what they like. Those told to drink water during the trial have, however, stuck with the habit – apparently, they like it. Strikingly, they have continued to lose weight (around 700 g over the year), whereas the other participants have put it back on.

Why this works is obscure. But work it does. It’s cheap. It’s simple. And unlike so much dietary advice, it seems to be enjoyable too. (From The Economist, August 28, 2010)

Script 4. Water purification

Any old iron?

A little-known chemical may provide a new way to clean water.

Iron in water is normally regarded a pollutant. Luke Daly, the boss of Ferrate Treatment Technologies of Orlando, Florida, however, plans to turn that thought on its head. He intends to use a chemically unusual form of iron to clean water up, not make it dirty.

Iron is found in the part of the periodic table known as the transition metals. Like all metals, these react with other elements by giving up electrons to form positively charged ions. Transition metals, though, give up different numbers of electrons in different circumstances, and thus have ions of various charges. Usually, iron loses two or three electrons. But in ferrates, which are compounds of iron and oxygen with non-transition metals like sodium and calcium, it loses six. That makes ferrates extremely reactive, and it is this reactivity which Mr Daly hopes to exploit.

First, ferrates are strong oxidizing agents. That means they destroy bacteria and viruses, and break up organic molecules with alacrity. Second, they are coagulants and flocculating agents. They attract other chemicals in the water, including dissolved metals, and precipitate them for easy removal. Moreover, once it has done its job, the iron in ferrates precipitates too, as iron oxide, leaving pure water behind.

The reason these wonder materials have not been used as water purifiers before is that their reactivity makes them unstable and thus difficult to store. Thomas Waite of the Florida Institute of Technology, an academic scientist on whose work the company has drawn, jokes that in the early days of his research he kept the whole world's supply of ferrates in a cabinet in his laboratory.

Ferrate Treatment Technologies' trick is to make ferrates on site, for instant use, rather than attempting to transport them to where they are needed. The firm's "Ferrator" uses three cheap raw materials - bleach, ferric chloride and caustic soda - to produce sodium and calcium ferrate at a price competitive, in terms of oxidizing power, with more familiar water-cleaners like chlorine and ozone.

A machine small enough to be carried around in a pickup truck, Mr Daly claims, could generate enough ferrates to purify 75m litres (20m American gallons) of water a day. The system is now being tested at two plants in Florida. If all goes well, the first commercial Ferrators will be up and running later this year. (From The Economist, January 22, 2011)