" A sol.n containing acetic acid, CH3COOH, and sodium actetate, NaCH3COO, is an example of this kind of buffer soln. The acidic component is CH3COOH. The basic component is NaCH3COO because the CH3COO- ion is the conjugate base of CH3COOH, The operation of the buffer depends on the equiibrium.
CH3COOH + H2O +---+ H30+ + CH3COO-
(high conc.) (high conc from salt)
When a strong base, such as NaOH, is added to the CH3COOH-NaCH#COO buffer solution, it is consumed by the acidic component CH3COOH. This occurs in the following way. The additional OH- causes the water autoionization reation to proceed to the left.
2H2O +---+ H3O+ + OH-
This uses up some H3O+, causing more CH3COOH to ionize.
CH3COOH + H2O +---+ CH3COO + H3O+ (shifts right)
Because the [CH3COOH] is so high, this can occur to a great extent. The net result is the neurtalization of OH- by CH3COOH.
OH- + CH3COOH -----+ CH3COO- + H2O (~100%)
added base acid weaker base water
"The solution, it turns out, would have to be very high is acetic, but not glacial, as it would need water. Here's some related info.
When we add 0.0010 mol NaOH
We have 1 L of original soln ph increases H3O decreases
Buffer soln +0.008 ph unit 1.2
(0.10 M NaCh3COO +
0.10 M Ch3COOH )
0.10 CH3COOH 0.91 8.1
Pure H2O 5.00 100,000
General Chemestry with Qualitative Analyses 6/e
2000 Harcourt College Pub. Orlando, FL.
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Basically, since such small changes in ph are possible using a buffered solution, differing alkaloids can be seperated based on the (minute) differences in ph.
The idea was mentioned in general in Indole Alkaloids, I don't have this around to ref the author or mention, but it was something like " A buffered soln was washed to yeild alkaloids of differing strengths based on their ph"
Today is opposites day. Everything I say, I mean the opposite.
