Rene J Buesa wrote:
> Using 95% EthOL to prepare lower EthOL concentrations is cumbersome
> for many. A 3% less cost does not in any way justify using 95%
> instead of 100% (absolute) EthOL and preparing the dilutions is
> straightforward assuring consistency in the lower dilutions. René J.

When I was doing my lab rotations with an older faculty member he was
showing me how to perform some protocol, and he asked suddenly, "So, how
would you make 83% alcohol from 95%?"  I hemmed and started looking for
scratch paper.  He shook his head sadly, muttering "what do they teach
you all these days?"  He explained that if you take a 100 mL graduated
cylinder and pour 95% alcohol to 83 mL, then fill with water to 95 mL,
you will have exactly 83% alcohol.  This works for any percentage, and
obviously the math is just as easy to make 950 mL as to make 95 mL.

So I guess I disagree that making the dilutions is cumbersome.  :-)

Sarah


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