Posts Tagged ‘Science Communication’

The Safety of Liquid Nitrogen Cocktails

October 28, 2012
Cocktails cooled with liquid nitrogen

Cocktails cooled with liquid nitrogen. Picture from Canadian Content

I was horrified to hear of the young woman, Gaby Scanlon, who suffered stomach injuries after drinking a cocktail laced with liquid nitrogen.

My interest in this case is to find out exactly how Ms. Scanlon came to be harmed. I often use liquid nitrogen for both scientific applications (cooling) and for scientific demonstrations. And over 30 years I have never heard of anyone who has suffered anything other than the most minor of injuries, so I was shocked to hear this news. How had it happened?

Liquid nitrogen can cause harm in one of three ways. The first and most obvious way is that it can cause cold burns. The second is that it can displace oxygen in the air and asphyxiate people. And the third is that it when it turns to a room temperature gas – which it can do rapidly – it increases in volume by a factor of roughly 600.

Normally the extreme cold is viewed as the primary hazard, but in fact that is usually not the case. The reason is that even though liquid nitrogen at -196 °C is extremely cold, on contact with objects at room temperature it immediately turns to gas. The gas has a low thermal conductivity and transiently insulates the hot object from the extreme cold. This film-boiling or Leidenfrost effect usually makes the handling of small quantities of liquid nitrogen extremely safe – much safer than the handling of hot coffee.

The effect is so strong that one can pour liquid nitrogen over one’s hand and barely feel the cold. However, after a second or two, the gas film collapses, and the cooling rate of the hot object increases dramatically. So prolonged contact – more than a second or so – with the liquid will rapidly cause cold burns or frostbite.

My speculation is that in this case, Ms. Scanlon swallowed the drink relatively quickly and because of the Leidenfrost effect, she recieved no feedback in her mouth about how cold the liquid was. The nitrogen would have travelled in droplets along with the cocktail into her stomach, probably relatively harmlessly. At this point the liquid – probably only a cubic centimetre of so – was trapped in a confined volume, and would have rapidly turned to more than 500 cubic centimetres of gas. I suspect it was this rapid expansion which caused the damage to her stomach.

Apparently the use liquid nitrogen in cocktails is commonplace. Wow! That passed me by! And so it is somehow shocking that Ms Scanlon was the first casualty – because there is no way to drink liquid nitrogen safely. But there is a way to safely consume drinks which are bubbling with gas and emanating large amounts of mist.

The key is to use dry ice -solid carbon dioxide – not liquid nitrogen. The difference is that liquid nitrogen floats on drinks – and so it is impossible to consume the drink without the possibility of ingesting a small droplet of the liquid nitrogen. In contrast, solid carbon dioxide sinks in water.

Michael de Podesta safely drinking 'potion'

Michael de Podesta preparing to safely drink ‘potion’

But there is a trick! The trick is to use both a glass and a liquid which are transparent and to put in just a single large piece of solid carbon dioxide. By large I mean roughly a cubic centimetre. The reason that a large piece is necessary is that the solid carbon dioxide immediately freezes water around it and if a small piece of solid carbon dioxide is used – the ice will cause the carbon dioxide to float. If prepared correctly one can see the single large piece of dry ice in the base of the beaker – and be sure that there are no other pieces lurking on the surface of the liquid.

Here’s to your health… Cheers

Protons for Breakfast 12

April 2, 2010
Protons Week 2: Looking at Light

Protons Week 2: Looking at Light

It is the evening of Good Friday 2010 and the 12th presentation of Protons for Breakfast finished on Wednesday. I am exhausted. Not so much from the course, but from the course on top of the hardest project on which I have ever worked.

The course was possibly the most successful yet, with the most attendees and the best retention rate. At the end of the course we collect feedback which is read by me and then included in a report to NPL management. I always find the feedback intriguing and this session’s is the typical. I can’t really post it all – there is too much, but I will post everything people wrote on two sections: One thing you have learned and Feedback for NPL Management. I post it here for you make of what you will. Reading this makes me want to do it better next time. And together with the team of fantastic colleagues, I will. But now I intend to enjoy a break – by which I mean devoting myself whole heartedly to my regular job!

One thing you learned…

  • What heat is?
  • Have broaden my understanding of physics from my a-level course. Also that mobile phones aren’t as harmful as I initially thought!
  • The Sun is bigger than the Earth!
  • Which way round the changes are in static electricity.
  • Not much.
  • Hard to think of just one thing – there are so many! Memorable moments; depiction of light-wave through sticks and jelly beans, heat hand-print on the wall (+ others). So the movement of light along a line of consecutive elements. And how one body affects another and for how long this lasts.
  • That mobile phone transmitters are nothing to be too worried about.
  • How atoms and particles act/react. How not to wear egg!
  • If you put an egg in a microwave and put a glass on it, leave it for a while then take it out, the egg explodes.
  • There are loads of atoms in our body.
  • That static will impact any material including wood and food stuffs.
  • That absolutely everything is electric!
  • All about infra-red and the global warming.
  • Eggs explode! Microwaves and telephones are not a problem.
  • Science is full of surprising facts.
  • Mobile phones.
  • Whatever the topic someone has written a song about it!
  • A lot.
  • Mobile phones experiments have all ended up inconclusive.
  • Where to begin – motion – that particles are in constant motion and it changes. How temperature changes the way particles move.
  • More about light spectrum.
  • That there’s atoms in everything apart from fields.
  • Duck eggs unreliable under stress.
  • Don’t put eggs in the microwave.
  • Mobile phones are not bad as I had thought.
  • There is electricity in everything.
  • Water bends!
  • About waves and mostly mobile phones. LOADS!
  • Loads about atoms.
  • How to make experiment.
  • Nuclear power.
  • How atoms and protons work.
  • I understand and can now argue about global warming. I was able to work out why a wok gets hotter than an frying pan.
  • Science is not scary! It’s all around us, from the air we breathe to the protons we drink.
  • That liquid nitrogen when poured briefly over skin will not burn or scald.
  • How make ice cream using liquid nitrogen.
  • I learnt how a mobile phone works and about infrared rays and how they ‘fry’ your brain.
  • Absorpion/emission of light emission frequencies/’jiggling’ + spectroscopy.
  • Different heats atoms move faster.
  • How to make ice cream out of liquid nitrogen.
  • That everything is electrical!
  • Atoms jiggle at different rates depending on whether it’s a solid/liquid/gas.
  • That water can hover.
  • A better understanding of how global warming is occurring.
  • I didn’t realise that every “single thing” had atoms. I was fascinated to learn about light electricity and heat.
  • We are all electric!
  • How weak the radiation from mobile phones really is.
  • How electrons and temperature work.
  • The theory behind atoms as being building blocks of our universe.
  • A lot about atom and how they’re moving when/when not being affected.
  • All that electricity everywhere!
  • Science is fun (world’s away from the dull and boring lessons I remember from school).
  • Lots about the application of science – I never thought I would understand oscillation and hertz.
  • The amount of fun with a microwave over (including Mr Egg).
  • The whole world jiggles.
  • Jelly baby waves!
  • Why energy saving light bulbs are saving!
  • That everything is made of atoms.
  • Light is a wave. Colour perception – loved Andrew’s slot in week 2.
  • That light is everywhere, and about phones! and how to spell ciao! Thanks for that ☺
  • Wave patterns – everything has electricity – that you can keep a metallic strip in the air with bursts of electricity. I wish I could remember some of the things I learned!
  • How mobile phones work. I have A level physics (1984) and so much had an air of familiarity but a fair proportion of it was new.
  • Temperature is a measure of the speed things are moving at.
  • Gherkins can conduct electricity! Different uses for electromagnetic radiation.
  • Lego men are cool …… being realistic ….. exploding eggs are cool.
  • How little I know.
  • Nuclear power ultimately stellar not solar.
  • The really neat way of describing the  relationship between electricity/heat/??? waves and atoms.
  • Too many to name!
  • That we are not running out of carbon fuels. I had thought that when the oil became scarce we would be forced to find more sustainable fuels – but oh no! Too much coal nothing to stop us overheating the planet, except ourselves.
  • How to get to the pub in 90 seconds. Many things. And especially developing understanding of how global warming occurs – and the small ????? proportion of carbon. And how mobile phones work.
  • Sausages conduct electricity.
  • Sausages conduct electricity.
  • I especially like week 1 (I sadly missed week 2 and 3) but for the first time I felt I had a skeleton framework to hang my science on.
  • Electromagnetic field, atoms and their purpose!
  • Atoms jiggle!
  • How large the sun is in relation to earth.

Is there any message you would like to give to the NPL management team…

  • No
  • Thank you for organising such interesting lectures – more should be able as it really enriched my learning in physics! I really enjoyed it!
  • I am very glad to have attended the sessions.
  • I understand this course was given by volunteers – I hope you give them a Christmas bonus!
  • Just thank you.
  • No. Thank you!!!!
  • How big is NPL?
  • Thank you for the opportunity!
  • Thank you!
  • Well done! And thank you.
  • A huge thanks for giving up your time and making this an interesting and entertaining course for a wide age group.
  • Thank you very much your all team members.
  • More courses like this! It’s a great way to engage with the local community.
  • You are the best!!!
  • You were all great, very smart, and a true inspiration. Everything was explained simply whilst not patronising, few people can do that. Thank you very much.
  • Do you have more ways of accessing what the NPL does. It would be fascinating to know/see more.
  • Michael and helpers v. enthusiastic.
  • Your doing an excellent job and keep it up.
  • Brilliant initiative. Wish more places did similar, credit to NPL.
  • Thanks, it was good.
  • Well done! And thank you!
  • See comment under ‘anything else’. Shouldn’t there be a museum on this site possibly linked to Bushy Park, Americans in WWII. If you want to talk about this I’m on
  • Need to let more schools know about the course. Keep doing this. Excellent course.
  • Fantastic course. You should blow your own trumpet more often about what happens here.
  • Great work!
  • No.
  • You guys are great!!
  • Brilliant. Please keep the talks! You are one of the only groups that makes adult lectures suitable for kids.
  • Publicise these much more widely. Take PfB on the road?
  • Thanks for a well run course.
  • You’ve done well.
  • This has been a fantastic experience. I wish you could do more outreach work to local state secondary schools.
  • Thank you – it has been great fun. Michael is an amazing presenter – so enthusiastic.
  • Keep up the good work!
  • The course is fantastic and I never learned anything at school. They should take in on tour.
  • Brilliant course, fantastically run by truly enthusiastic people.
  • Thank you very much for the time and effort you put in to this course. It is wonderful. Thank you very much Michael.
  • I think these sessions are a great way of bringing science to life for kids and making creating some excitement about the topic. I work at BP (here as a parent) but I am involved with the BP schools link scheme. I have told my link school about this course and the BP ext affairs people.
  • No, not really! But I like your powerpoints. Very well done!
  • Keep it up.
  • This has been the most amazing course. Keep employing these wonderful people.
  • I am now truly able to share Michael’s immense passion for physics! Physics Woo!!
  • No.
  • I admire your engagement and enthusiasm.
  • Thank you for all your hard work this is a very valuable.
  • What a super way to advertise what NPL is all about,  why you exist and why science is ???
  • Thank you very much for all efforts have been done!
  • The course should be filmed and shown in schools. If every one knew about it the demand would be huge. Same about people attending in person. Michael is a star and his enthusiasm infectious. His powerpoints were brilliant. Michael is the Jeremy Clarkson of the Physics World.

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