pHing sodium Acetate

klein at mpimg-berlin-dahlem.mpg.de klein at mpimg-berlin-dahlem.mpg.de
Thu May 19 16:13:56 EST 1994


In article <DennisonC.6.2DCE9FD0 at biochem.unp.ac.za>, DennisonC at biochem.unp.ac.za (Clive Dennison) writes:
> In article <1994May4.161959.4328 at tower> afc at gnv.ifas.ufl.edu (Andrew Cockburn) writes:
>>From: afc at gnv.ifas.ufl.edu (Andrew Cockburn)
>>Subject: Re: pHing sodium Acetate
>>Date: 4 May 94 16:19:59 -0500
> 
>>In article <GREENWOODP.1.0010A911 at AGRESEARCH.CRI.NZ>,
>>GREENWOODP at AGRESEARCH.CRI.NZ (Penny Greenwood) writes:
>>> hi, We're having great difficulty getting 3M NaAc to pH 4.0, for use in a 
>>> polyA-enriched RNA extraction procedure. If anyone has any ideas or advice
>>on 
>>> how to achieve this please reply to the net.
>>> 
>>> Cheers Penny and happy little new netter Laurel.
> 
>>This is going to be about half HAc at this pH.  You could figure it out and
>>add the appropriate amounts of HAc and NaAc, or you could do it the lazy
>>way:
> 
>>Make up a 3M solution of HAc.
>>Make up a 3M solution of NaAc.
>>Mix the two until you get to pH 4.0.
> 
>>This is assuming that it is supposed to be 3N Ac-, not 3N Na+.
> 
>>Andrew Cockburn
>>USDA
> 
> Or, why not start with HAc, that will be 3M when made up to volume, make up 
> nearly to volume, titrate with NaOH of arbitrary concentration and then make 
> up to volume.  This approach works with most buffers and cuts down on the 
> number of weighings, etc.
> 
> Have pHun, 
> Clive - Biochemistry, Univ. of Natal.
----------------------------------------------------------------------------
Sodium acetate-acetic acid buffer (1 M), pH 3,6-5,8
      Walpole, J.C.S. 105, 2501 (1914)

Na acetate, 3HOH, M.W.=136,09 

......................................................
                 I    1M sodium    I                 I
pH at 18"C       I     acetate     I  1M acetic acid I
.................I.................I.................I
                 I      (ml)       I      (ml)       I
    3,6          I      0.75       I      9,25       I
    3,8          I      1.20       I      8,80       I
    4,0          I      1,80       I      8,20       I
    4,2          I      2,65       I      7,35       I
    4,4          I      3,70       I      6,30       I
    4,6          I      4,90       I      5,10       I
    4,8          I      5,90       I      4,10       I
    5,0          I      7,00       I      3,00       I
    5,2          I      7,90       I      2,10       I
    5,4          I      8,60       I      1,40       I
    5,6          I      9,10       I      0,90       I
    5,8          I      9,40       I      0,60       I
.................I.................I.................I

Live long and prosper....


Mathieu Klein




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