BUILDING an Alka-Seltzer bomb to enliven an evening in the pub is all in a day's work for Dr Frank Burnet of the University of the West of England.
It's more than a bang - it's a chemistry experiment. So when Dr Burnet was asked to bring science to the people as part of National Science Week, he reasoned that "the people" are often found down the pub, and the pub is a hotbed of chemistry, physiology and physics, so that's where he should go.
He and his team have produced a new science, boozology, which is being introduced in Bristol pubs this week. The experiments require only a rickety, beer-stained table for a lab bench - and a pint glass and matches instead of test-tubes and Bunsen burners. There is a quiz as well, known as Pub Genius, which can elevate inebriation to a quest for knowledge.
"Make sure to retire to a safe distance," says Dr Burnet before explaining how to build a bomb from an indigestion tablet.
Put one Alka-Seltzer into a little container - old film containers, by good fortune, are exactly the right size, he says. Add a little water and fix the lid on properly, then be sure to follow his advice about backing away . . .
"The top will come off in a 'boom' rather than a 'flip'," explains Dr Burnet. After the bang, you can repeat the experiment with the same tablet. This time there will be a time-delay of about 30 seconds before the explosion.
Once the excitement is over, Dr Burnet, senior lecturer in the public understanding of science, explains why it happens. "The main ingredient of Alka-Seltzer is sodium bicarbonate," he says, "and in water it dissolves, releasing carbon dioxide. If you leave a lid on, it has nowhere to escape, so it builds up." Eventually, the pressure lifts the lid off.
If that is too easy, then Dr Burnet has something a little more refined: the mysterious self-elevating lemon.
For this trick, you will need an ash-tray with deep sides. Add water to at least half an inch deep. Take a slice of lemon and stand five matches in it. Then light the matches and cover the whole apparatus quickly with a pint glass.
The matches will burn for a while and then, magically, the lemon will rise up the inside of the pint glass. "When you burn anything in air, it uses up the oxygen and creates a partial vacuum which sucks fluids," he explains.
If the exertion of pub experimentation makes you reach for a drink, Dr Burnet and his team of boozologists will be trying to deepen your understanding of the chemistry of alcohol.
Wine rarely comes at a strength of more than 12 per cent alcohol, apart from the Japanese wine sake. The reason lies in the yeast, says Dr Burnet, which gobbles up sugar for energy, "excreting" alcohol as a result. Alcohol is not very pleasant to live in and once its level reaches 12 per cent, the yeast is killed off. "It's about as much as the yeast can bear," he says.
The yeast used in sake, which can have an alcohol content of up to 25 per cent, is combined with a variety of other fungi. Scientists are interested in increasing the alcohol-tolerance of yeast because the more alcohol the organism can tolerate, the more alcohol can be brewed.
Still on the subject of wine, Dr Burnet asks: why do reds come in green bottles? Ostensibly, this is to protect the brew from the effects of daylight, which could attack the pigments from the skins of grapes and cause them to fade. But, true to form, scientists disagree over this one - some say wine comes in green bottles simply because it has always done so and no one would buy red wine if it came in a clear bottle.
Later, Dr Burnet addresses a question that perplexes moderate drinkers everywhere: how do you keep the state of moderate inebriation topped up without becoming more drunk or lapsing back into sobriety? Mathematics and basic biology are the key, he says. "The liver is where alcohol is destroyed. It's like a bilge pump, and it can destroy half a pint's worth of alcohol - or one unit - an hour." So sobriety creeps up on the drinker at a rate of one unit an hour and can be fended off by drinking at the same rate.
Extending the mathematics, Dr Burnet asks pub-goers how long they would have to wait after drinking eight pints of beer before they could pass a breathalyser test. The precise answer, of course, depends on how long it took to drink the eight pints, but the rough answer is 12 hours.
Every drink mix, too, is a little chemistry experiment waiting to be explained. The boozologists can explain what goes on at the bottom of a glass. Why does Pernod go cloudy when water is added? Because Pernod contains aniseed extract, which is more soluble in alcohol than water and comes out of solution when extra water is added.
The evening wears on and, making themselves useful, the boozologists dispense advice on hangovers. As pub-goers head for the lavatory, Dr Burnet observes that the average person passes between one and a half and two litres of alcohol each day.
"One thing that certainly works [against hangovers] is drinking water," says Dr Burnet. "Alcohol makes you pass water, so if you take alcohol you actually lose more fluid than you take in."
Alcohol inhibits a hormone called vasopressin, which controls how the kidneys reabsorb water. As a result, more water passes to the bladder. If you drink two glasses of wine, you lose about four glasses of water from the body in the next two hours.
