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Science LinX Pre University Students DIY Science Science experiments

And the herring gave light...

Episode 9

You don’t always need a big laboratory for exciting experiments... You could, for example, make a gherkin produce light.

Topsy had beaten three men to death, two zookeepers in Texas and an animal trainer in the circus where she worked. He had fed her a burning cigarette, upon which she grabbed the man with her trunk and beat him against the ground. The beating was fatal.

Can you really blame Topsy? Nevertheless, the authorities in the state of New York decided that the elephant had to be put down. But how do you kill an elephant? The entrepreneur and inventor Thomas Edison recommended that Topsy be electrocuted. Edison’s suggestion was a cynical marketing stunt in the fierce battle he was fighting with George Westinghouse. Around 1900, the two were competing for dominance of the American electricity market; Edison with direct current and Westinghouse with alternating current.

To demonstrate that alternating current was unsafe, Edison used Westinghouse’s system to electrocute all manner of animals – cats, dogs, monkeys and cows. He even succeeded in convincing the state of New York to use alternating current for the newly introduced electric chair and he tried to introduce the term ‘Westinghoused’ as an alternative for ‘electrocuted’.

On 4 January 1905, Topsy was electrocuted in an amusement park on Coney Island. The War of Currents had by this time really already been decided in Westinghouse’s favour, and today practically the whole world uses alternating current.

Was Edison’s direct current safe? No idea. But the use of 220 volt alternating current for kitchen experiments certainly isn’t. The following experiment is only suitable for those who have experience working with electricity and who know what they are doing. Please read the disclaimer first.

Hammer two big nails (3.5mm) into a slat about five centimetres apart and screw the slat with the nails pointing up onto a stable plank. Attach the ends of a length of electric wire to the nails with connectors and connect the other end to a plug (don’t plug it in a socket yet!). Then take a gherkin and spike it on the nails. Now you can put the plug in a socket.

In the Cogito ergo boom! lab this initially resulted in... nothing. Then, after fifteen seconds or so, the gherkin started to steam, spatter and, accompanied by cheers from the onlookers, started emitting orange light.

The gherkin is good at conducting electricity because of the acid and salt in which it is pickled. The editors of Cogito ergo boom! came to the conclusion that the experiment should work on other pickled food products too. And what transpired? A pickled herring folded double produces orange light if you run 220 volts through it. What follows is a disgusting smell of burnt fish, then it starts smelling of cooked vinegar and finally, with a loud bang, it causes a short circuit.

And then you need to keep your face straight while you explain to someone from the technical support service what happened. But what’s important is: it’s possible!

But why does a herring produce light? The most plausible explanation is that it heats up at the electrode (the nail). This causes a vapour to rise up the electrode and this creates a space between the electrode and the herring. The light that you see is sparks jumping across that space. This theory appears to be confirmed by minuscule damage done to the nails during the experiment.

The orange colour of the light produced by the gherkins is caused by the sodium in the salt used to pickle them. For the enthusiasts: this light has a wavelength of about 600 nanometres. The same deep-orange colour can be seen in street lights along the motorways – these are indeed sodium lights. Although it is unlikely that these lamps work with gherkins. Or pickled herring.

Author: Ernst Arbouw

Last modified:12 April 2021 1.14 p.m.
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