Temperature & Video Friday

A few months ago* I’m a Scientist asked for people to name how many elements in the periodic table were liquids at RTP.  Mercury and bromine obviously…or is it?

The key is in the question and I’m going to be pedantic.  RTP stands for room temperature and pressure which is really going to depend on how we’re defining room temperature.  Put another way – a lab in Scotland in the winter is probably going to have a different room temperature to a non-air conditioned lab in California in the middle of summer.  RTP is often used interchangably for STP.  Standard temperature and Pressure is clearly defined as 273 K (0 degC) and 100 kPa (0.98 atm) by IUPAC, and as 293 K and  approx. 101 kPa (1 atm) by NIST.  Under either of those definitions 2 elements as liquids is correct.

The one that doesn’t belong (and where we need to take care to define ‘room temperature’) is gallium with a melting point of 29.7 deg C.

And that brings me to Video Friday…watch this then read on!

Anyway, all of this got me thinking about the temperature at which we conduct reactions. In general chemists use quite a limited range of temperatures for reactions, governed mainly by convenience.  Those tend to be: freezing point of water with or without specific additives (like salt), boiling point of specific solvents (or mixtures of solvents and reagents – reflux), other sub-zero (deg C) temperatures achieved by combinations of dry ice (solid carbon dioxide) or liquid nitrogen with solvents or additives.  I don’t remember ever seeing a procedure that required a constant temperature of 15 degC which is just as well because it would be quite difficult to achieve.

A lot of reactions are just done at room temperature, no more specific than that.  It is usually an indication that the reaction requires neither heating nor cooling and therefore can happily sit on the bench.

* yes, the bulk of this post has been sitting in the drafts folder since July waiting to be finished off.  Disgraceful!

3 Replies to “Temperature & Video Friday”

  1. Doesn’t Caesium have a similar melting temperature to Gallium? Why don’t they repeat the experiment with one of those spoons?

  2. I recently attempted to repeat work from 2 separate publications – one at 15’C and one at 13.5’C and yes, it is very hard to achieve. I sort-of managed it using a hot water bath and an open window. Luckily the reaction didn’t work as reported so I shouldn’t have to stand in that room with the window open during a Scottish winter again.

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