December 16, 2013

Advent Chemistry: Titration

Titration is, like most of the concepts I’ve covered this year, basically quite a simple trick. You take an unknown amount of something, and you add somethig it reacts with in small, known amounts, until the reaction stops. Then you know how much of the...

December 15, 2013

Advent Chemistry: Dropwise

Sometimes – often – there are no shortcuts. If you wan to get the best results, you have to take time over them. You have to let your mixture reflux for long enough. You have to dry it off in the oven until it’s properly...

December 13, 2013

Advent Chemistry: Magnetic balances

One of the more curious devices in a chemistry lab is the magnetic balance. This is an extremely precise balance – as in, accurate to the nearest hundred thousandth of a gram or closer – with an electromagnet underneath. The balance lives in a nearly...

December 12, 2013

Advent Chemistry: Piping hot

I’ve mentioned concepts like making things hot before, but I haven’t gone into detail about how. The rather charming image of a chemist in a dark laboratory, tending to a bunsen flame, while the varnish on the wooden bench gleams in the light, and green...

December 11, 2013

Advent Chemistry: Hot Filtration

Filtration, like recrystallisation, is about physically seperating things. It’s not about doing a reaction. It’s just a way of getting the thing you want in a pot on its own. If what you want is solid, and everything else is liquid, this is quite easy,...

December 10, 2013

Advent Chemistry: Recrystallisation

Once you’ve collected your product, in its lovely freshly-grown crystal form, you need to purify it. This first version is full of bits of unspent reactant and solvent and side products and waste products, and everything would be better if it were not. Washing it...

December 8, 2013

Link to Precipitation

Advent Chemistry: Precipitation

Precipitation, when it doesn’t mean rain and snow, means roughly the opposite of dissolving. It means taking a solution, and persuading the interesting thing to come back out of solution and be a solid. We already covered rotary evaporation, which is one way of doing...

December 7, 2013

Link to Distillation

Advent Chemistry: Distillation

Distillation has a lot in common with reflux, except that instead of letting the condensate drip back down into the original mixture, you change the layout a bit and collect it into a second flask. Distillation is the usual method of making spirits from weaker...

December 6, 2013

Link to Refluxing

Advent Chemistry: Refluxing

As a general rule, heating a reaction up makes it go faster. Many reactions work better if you boil the solvent they’re happening in. Actually, many reactions happen fastest of all in the vapour that comes off the boiling solvent. The reaction takes place in...

December 5, 2013

Link to Rotary Evaporation

Advent Chemistry: Rotary Evaporation

Consider this: You’ve got a flask of liquid. In the flask is some solvent, and dissolved in it (along with probably some leftover bits and pieces of raw material that you don’t care about) is your product. How do you get the product out? You...