MadSci Network: Chemistry |
I personally have a real moral dilemma with this sort of question. Liquid oxygen is an EXTREMELY dangerous material. It is perilously easy to produce using liquid nitrogen and ordinary air. I really would not want to post such details on an open web page. I do not have the details at my fingertips -- would need to go away to search for them anyway. On the other hand I believe in the free flow of information and am against censorship in general principle, if not always in detail. In instances like this, I think that the need to have enough knowledge and resources to find the recipe for oneself (it is certainly available in the public domain) might be a useful filter in restricting the details to those who might have enough intelligence and responsibility to use the knowledge wisely. Oxygen gas is about 21% of ordinary air. At ordinary temperatures, a mole of oxygen gas in air occupies about 120 litres. When condensed to a liquid, a mole of oxygen occupies about 60 mL -- that is, it is 2000 times more concentrated. Of course at liquid oxygen temperatures, many chemical reactions go very slowly. But most oxygen reactions involve free radicals. And free radical reactions are often not much affected by temperature. So there is the potential for a reaction to get started if any combustible material contacts liquid oxygen. And if it does get started, the high oxygen concentration will produce dramatic and disastrous effects. There will be a huge concentrated supply of oxygen present to sustain any reaction that does get started. The heat produced from the reaction will cause rapid evaporation of the liquid, accompanied by a 2000-fold expansion. The probable result will be an explosion with spot fires at the periphery. It is almost certain that insurance would not cover damage to any premises or property where liquid oxygen was being prepared or used. When I started my University studies in Australia in the early 1960s, liquid air (not liquid oxygen, but about 20% liquid oxygen in nitrogen) was still being used as a coolant for vacuum lines and the like. Everyone was terribly scared when using it, and there were tales of some awful accidents. It was universally replaced with liquid nitrogen around 1965, and use of liquid air was discontinued.
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