Saturday, August 30, 2008


I like to know the derivations of the terms I learn. During my first year of chemistry I discovered the word “pnictogen”, and spent a lot of effort discovering its meaning.

Likewise, I like to know where the trivial names of the fatty acids come from.

Let’s start with the saturated fatty acids:

  • Butyric acid(C4:0) (Four carbon atoms in the chain, no double bonds.) This name comes form butter, because the nasty smell of rancid butter comes from this fatty acid. Of course, with the short carbon atom chain it is pretty volatile.
  • Valeric acid. (C5:0) This name comes from Valerian, a perennial flowering plant. The free fatty acid has a very unpleasant odour, but its esters give valerian its pleasant odour.
  • Caproic acid (C6:0)
  • Caprylic acid (C8:0)
  • Capric acid (C10:0) These three fatty acids are named from the Latin caper, or goat. As you can imagine, these don’t have a pleasant odour.
  • Lauric acid (C12:0) Lauric acid is named after the laurel, in which oil it is found. The more common source however is coconut oil
  • Myristic acid (C14:0) This fatty acid is named after nutmeg, Myristica fragrans.
  • Palmitic acid (C16:0) Palmitic acid is name from the French palmitique, ultimately from the Latin palmus or palm. Of course it is one of the main constituents of palm oil.
  • Stearic acid (C18:0) Named after tallow, which in the Greek is stéar.
  • Arachidic acid (C20:0) This has nothing to do with spiders. The Latin word arachis means peanut.
  • Behenic acid (C22:0) This comes from a variant spelling of ben oil. This fatty acid is only a minor component of ben oil, but it was named after it because it was first discovered in the oil.
  • Lignoceric acid (C24:0) The Latin origin of this fatty acid’s name would translate into “wood wax”.
  • Cerotic acid (C26:0) Ultimately from the Greek keros or wax (which also gave us kerosene). Free cerotic acid is found in beeswax.

Wednesday, August 27, 2008

Conduction, radiation and ... yes, convection!

Today I discovered that the inlet and outlet legs of the GC column heat up to the set temperature quicker if the fan of the oven is switched off.

Tuesday, August 26, 2008

It needs to be long enough

Today's discovery: I discovered that when a quartz capillary is used in the place of a needle, it need to be about as long as the needle. At the very least it needs to be long enough to pierce the septum. Ten millimetres is not long enough. There's no point in getting the flow right but you can't get it inside the instrument.

Monday, August 11, 2008

Odd flow

Today I discovered two things. The first is a leak. This was fairly impressive: my prof and I stood at the whiteboard and discussed the symptoms, and diagnosed a leak as one likely thing that should be checked for.

The second thing I discovered is that when the valve says clack it does not necessarily mean that it is open. A bubble check told me that reality did not correspond to the computer screen. Suddenly the split inlet acts like a split inlet.

Monday, August 04, 2008


Today I discovered that the septa that we've been having problems with are actually 12 mm in diameter, and not 11 mm as the manual specifies. It explains a lot, amonst other things why the silicone gets squeezed into the most darned spaces when coring occurs.