Tuesday 27 October 2020

The death of butane

Down the rabbit-hole: you never know where you'll pop out. Because National Math Week, I was writing a little teaser about mathematical series and suddenly we were back to chemistry class 50 years ago. You might think that iso-butane, the branched carbon backbone version of n-butane, would be chemically identical: they are both C4H10 after all. It's subtle but they are different in their physico-chemical properties.

Name Propane iso-Butane n-Butane
BP°C -42°C -11.7°C -0.5°C
Vap.pressure 859kPa 215kPa 311kPa
Sol.water 47mg/L 49mg/L61mg/L
Butane is not much good in Nunavut or Siberia during the winter, because it won't vaporise in freezing temperatures. Propane is more volatile and so handier in those chilly circumstances. Iso-butane [-11.7°C] is a superior fuel compared to n-butane and there is indeed a price premium on it. Vapour pressure otoh is much less for butanes than propane and so butane is the alkane of choice as a propellant. Propel what? Bullets! [it's a boy thing].

I've lived a very sheltered life, and a privileged one, too. It never occurred to me that solvent abuse was an option. But it seems that "Inhalation of butane can cause euphoria, drowsiness, unconsciousness, asphyxia, cardiac arrhythmia, fluctuations in blood pressure and temporary memory loss". Jakers! I can only imagine doing butane if I had a very short attention span and stopped reading the effects list immediately after "euphoria". Butane is readily absorbed through the lung epithelium and its solubility in water/plasma is about the same as oxygen [40mg/L], and like oxygen it can cross the blood-brain barrier and start tricking about with the neurotransmitters and their receptors.

The problem is that when "they" spray liquid butane directly down the gullet it gets colder as it vaporises and can deliver -20°C to the wet epithelium. That causes a laryngospasm as the vocal chords clamp shut to protect the even more delicate lung tissue from freezing. It's call SSDS sudden sniffers death syndrome and causes about half the deaths each year among the inhalant community.
DON'T DO THIS AT HOME: effin' heartfelt plea from survivor. Another confessinfo from chemistry Prof who got high on white-board markers - it's the xylene, silly!

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