On the subject of sugars, it's easy to believe that granulated white and caster sugar are made from the same thing, just ground to different fineness', as they taste and feel the same. Is icing sugar made from the same original sugar? I'm assuming it is, and if it is, why does making the sugar really fine (i.e. making icing sugar) make it taste very different to other sugars?

Some sources say that carbon dioxide has no taste or smell but others say that it is acid/sour (this is the same word in German).

I think the latter are right in every aspect because if you open a bottle of sparkling water and let the gas above the water into your mouth it definitely tastes sour.

But why are there sources that say it has no taste or smell? Do they just mean you can't smell it in the concentration in which it is present in rather bad air? Or do they mean that the gas itself is neutral to our receptors, and they respond only to the carbic acid it forms with water? But it would be rather difficult to try to smell/taste DRY carbon dioxide, wouldn't it?

It's happened a couple of times now that directly after I have a vaccination (the most recent was the rabies vaccine) that I get a slightly acrid taste in my mouth. What causes this?

What I mean by that is, when you eat or drink something (eg. a chilli) sometimes you only get the spicyness after a while. This also happens with cranberry juice- you get a bitter aftertaste.

Why does this happen?

We're all no doubt familiar with the somewhat metallic taste of blood, but seeing as the tongue has a healthy supply of the stuff, how can it detect it at all?  Surely the tongue should be so used to the presence of blood that any extra should effectively taste of nothing at all?

Most of us will be familiar with the somewhat metallic taste of blood, but how are we able to detect the taste of blood at all, when the tongue already has a healthy supply of the stuff?  Surely with this blood supply adding itself to the taste of everything we, er, taste, then blood itself would effectively taste of nothing?

I live part of the year in an area with chlorinated water, and part of the year in an area with well water. For a few days when switching from chlorinated to well water, the well water tastes bitter. After awhile, the well water tastes delicious. Bottled water also tastes bitter when I've been drinking chlorinated water. What’s going on with my taste buds?

When I have an upset stomach, I sometimes take a strong mixture of baking soda and water. Immediately after drinking this nasty, salty concoction (which works very well, by the way), I drink plain water to wash the taste away. This water invariably tastes extremely sweet, as if it contains sugar. What’s going on with my taste buds?