Church hyb solution questions

Edwin Fink fink at
Wed Mar 8 11:48:30 EST 1995

> Date:          8 Mar 1995 10:36:02 GMT
> From:          bckraev%wawona at ("Alexander Kraev" bckraev at
> Reply-to:      bckraev%wawona at ("Alexander Kraev" bckraev at
> To:            "bionet.molbio.methds-reagnts mail newsgroup" <bionet-news at>
> Subject:       Re: Church hyb solution questions

> In article <D50nuE.1DA at>, Anthony Tomlinson <tomlinson at> writes:
> >In article <3j7due$mca at> Glen Shearer,
> >gshearer at writes:
> >>
> >>Just mix equal molar amounts.  0.5 mole/L monobasic + 0.5 mole/L
> >>dibasic and there's your 1M stock.  For the hyb soln' mix up
> >>2 parts NaPO4 stock, 1 part water, 1 part 20% SDS.
> >>
> In the original paper it is suggested to titrate Na2HPO4 with phosphoric
> acid to pH 7.2. The only difficulty you may get here is that this chemical
> is available with 2H2O and 10H2O, so watch the MW on the bottle. And, 
> although it is kind of textbook reminder, "1 M Na2HPO4" is 1M with respect
> to sodium and 0.5 M in phosphate, so in practice you divide the MW by 2 and
> weigh that out to be dissolved in 1 liter. It is impossible to dissolve one
> mole of this salt in 1 liter at r.t., but I saw many people hopelessly waiting
> by the stirrer for it! Cheers,
> *************************************************************************
> Alexander Kraev, Ph.D.                 Internet: bckraev at
> Lab. of Biochemistry III               Phone: 0041-1-632-31-47
> Swiss Federal Institute of Technology  FAX:   0041-1-632-12-13
> Universitaetstr.16
> CH-8092 Zurich
> "Some ideas are obscure not because they are complex, but because they 
>  are excluded from our circle of comprehension" - Kozma Prutkov

Sorry, Alexander, but I have to correct you:

"1 M Na2HPO4" means that 1mol of Na2HPO4 is contained in 1 l of 
solution, thus the solution is 2 M in  Na and 1 M in PO4. But, of 
course, if you need a solution which is 1 M in Na than you titrate a 
0.5 M Na2PO4 with phosphoric acid as originally described.
Cheers,    Edwin
Edwin Fink
Department of Clinical Biochemistry
University of Munich
E-Mail: fink at
Tel.: +49 89  5160 2601
Fax:  +49 89  5160 4735

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