bicarbonate of soda / soda crystals

[John Stumbles]

I wonder if bicarb is an ingredient of dishwasher detergent which is also very good for degunking teapots and vacuum flasks?

[Owain]

Denture tablets are good for teapots etc.

Owain

[Stuart Noble]

So is Ribena oddly enough, it being acidic

[Andrew Gabriel]

Dishwasher detergent is normally a strong alkali, based on caustic soda and other ingredients.

[Andy Hall]

This is an area where there is a lot of marketing.

A recently purchased pack of dishwasher cleaner claimed to have X% of non ionic surfactant which all sounds very innocent and like the instruction book for a 1960s girl's chemistry set.

Reading in more detail and looking at the MSDS revealed that it was our old friend, NaOH. No other ingredients were mentioned.

[Clive George]

That'll be what does some of the work, but there will be a non ionic surfactant as well, since NaOH doesn't fit that definition at all.

cheers, clive

[Andy Hall]

I see.

What things fall within that definitiion?

[Andrew Gabriel]

A wetting agent, like a detergent (except they are more commonly ionic surfactants). It's a long time ago since I knew this, but IIRC ionic surfacants tend to foam easily as they skin over water one molecule thick with the charged end of the molecule in the water and the uncharged end sticking out, aiding bubble formation. This is a bad thing in a dishwasher as anyone who's tried using regular washing up liquid in one will tell you. Non-ionic surfactants don't do that.

The surfacant ensures the food can be quickly wetted by the caustic soda, so it can quickly get to work on it. The surfacant also has cleaning properties in that it can break dirt down into small particles and surround it, making it appear to be soluable when in fact it isn't by itself.

[Stuart Noble]

A domestic cleaning product is only likely to contain sufficient caustic soda to make it alkaline i.e. bugger all. It has to be mentioned in the safety data though, whereas the main ingredients are probably not considered hazardous. IIRC surfactants are either non-ionic (non-foaming), anionic (foaming), cationic (forming a film on the surface- hair conditioner etc). I remember an occasion many moons ago when every hotel room in London was taken because of a....surfactant conference. Obviously very big business, even then.

[Andy Hall]

OK.

By dishwasher cleaner here I meant the product that can be put in periodically to clean the machine itself.

[Clive George]

Makes no difference. You still don't want a foaming surfactant. You could well have more NaOH to attack the stubborn stuff a bit more, but that still doesn't make it a) non-ionic b) a surfactant, or c) miscible with oil/grease. You still need the surfactant as Andrew said above.

cheers, clive

[Frank Erskine]

Water?

:-)