Carbonate/bicarbonate buffering of ph

[caliban07]

I recently read an article that a buffer that increases alkalinity to achieve a desired ph has it's in preferred ph value.

For example, sodium bicarbonate holds water at a ph of 8.4.

The article also went on to state that buffers don't always raise ph they can lower it too.

The article states:

"Below 8.4, Bicarbonate absorbs H+ ions and the equation moves to the left, making the water more alkaline. This continues until the pH reaches 8.4 when the process stops.

Above 8.4, Bicarbonate releases H+ ions and the equation moves to the right, making the water more acidic. This continues until the pH is 8.4 when the process stops"

The second paragraph doesn't make sense. How can bicarbonate release H+ ions and move ph down if we are adding a base?

Here is the full article it's only a page long.

(link removed by Borek)

 

[Borek]

My advice: don't bother, this article is full of nonsense.

Actually it is so bad I am deleting the link from your post.

 

[caliban07]

My advice: don't bother, this article is full of nonsense.

Actually it is so bad I am deleting the link from your post.

Ok perhaps you could provide me with a more accurate link?

 

[Borek]

Chemguide is typically OK:

http://www.chemguide.co.uk/physical/acidbaseeqia/buffers.html