[Nhcoll-l] Acidity in alcohol

[Dirk Neumann]

Dear Nicolas,


it might be worth to compare the attached paper; my colleague did some 
tests which are summarized therein. Normal pH-paper tests will not work, 
you need to dilute the alcohol to get reliable measurements (see 
attached paper).

If your tap water is not chlorinated and pure but calciferous, you might 
dilute your 96% EthOH with tap water to 80%; the dilution needs to rest 
for at least one day, as calcium carbonate starts to precipitate; the 
residual carbonate in solution gives you some sort of buffer capacity.

Hope this helps
Dirk


Am 18.10.2016 um 16:00 schrieb Margraf Nicolas:
>
> Dear all,
>
> The MHNC is a small natural history museum located in the hearth of 
> the Jura Mountains in La Chaux-de-Fonds, Switzerland. The MHNC team is 
> currently re-conditioning the alcohol collection, changing containers 
> and alcohol using an 80% Ethanol solution. The team was told to check 
> the acidity of the alcoholic solution as acidity is not good for the 
> specimens but had trouble doing so.
>
> Is a 9.6 mg/l acidity expressed as acetic acid too acidic? (12 mg/l in 
> 96% Et-OH diluted to 4/5)
>
> Additional questions:
>
> The alcohol dealer was asked about the acidity of the 96% Ethanol he 
> provides us with. The value he gave us is 12 mg/l of acidity expressed 
> as acetic acid. We tried to calculate the pH based on that value and 
> obtain a value of 4.23. Does that sound right?
>
> We tried measuring the pH of the solution with both pH-paper and a 
> pH-meter and found conflicting values. Is the pH-paper reading valid 
> for an alcoholic solution? Or is the pH-meter value valid for an 
> alcoholic solution?
>
> A pH of 4.23 seems too acidic to preserve specimens so we tried to 
> calculate the amount of Na2CO3 necessary to neutralize the 12 mg/l of 
> CH3COOH and obtain 10.6 mg/l. Is it correct (and sufficient) to add 
> this amount of Na2CO3 to every liter of our 96% Et-OH solution?
>
> Any advice or help would be greatly appreciated.
>
> Thanks,
>
> Sincerely,
>
> N
>
> *****************************************
>
> Nicolas Margraf
>
> Collaborateur scientifique
>
> Musée d'histoire naturelle de La Chaux-de-Fonds
>
> Av. Léopold-Robert 63 - CH 2300 LA CHAUX-DE-FONDS
>
> T +41 (0)32 967 60 71 - mhnc at ne.ch <mailto:mhnc at ne.ch>
>
> www.mhnc.ch
>
>
>
> _______________________________________________
> Nhcoll-l mailing list
> Nhcoll-l at mailman.yale.edu
> http://mailman.yale.edu/mailman/listinfo/nhcoll-l
>
> _______________________________________________
> NHCOLL-L is brought to you by the Society for the Preservation of
> Natural History Collections (SPNHC), an international society whose
> mission is to improve the preservation, conservation and management of
> natural history collections to ensure their continuing value to
> society. See https://urldefense.proofpoint.com/v2/url?u=http-3A__www.spnhc.org&d=CwID-g&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=awiDiMv0NtCLLz5-uNP7bpumXx_y47hSNPzjP1ztGHQ&s=ah02X65SM_HBrY5-9DCrbp-5750s6QV7TN5G1ffufrM&e=  for membership information.
> Advertising on NH-COLL-L is inappropriate.


-- 
Dirk Neumann

Tel: 089 / 8107-111
Fax: 089 / 8107-300
email: Dirk.Neumann(a)zsm.mwn.de

Postanschrift:

Staatliche Naturwissenschaftliche Sammlungen Bayerns
Zoologische Staatssammlung München
Dirk Neumann, Sektion Ichthyologie / DNA-Labor
Münchhausenstr. 21
81247 München

Besuchen Sie unsere Sammlung:
https://urldefense.proofpoint.com/v2/url?u=http-3A__www.zsm.mwn.de_ich_&d=CwID-g&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=awiDiMv0NtCLLz5-uNP7bpumXx_y47hSNPzjP1ztGHQ&s=ZAb7gDSyAGwhQGWD5e_OD-UJZa03v9DimjLmwivi2aM&e= 

---------

Dirk Neumann

Tel: +49-89-8107-111
Fax: +49-89-8107-300
email: Dirk.Neumann(a)zsm.mwn.de

postal address:

Bavarian Natural History Collections
The Bavarian State Collection of Zoology
Dirk Neumann, Section Ichthyology / DNA-Lab
Muenchhausenstr. 21
81247 Munich (Germany)

Visit our section at:
https://urldefense.proofpoint.com/v2/url?u=http-3A__www.zsm.mwn.de_ich_&d=CwID-g&c=-dg2m7zWuuDZ0MUcV7Sdqw&r=CLFZJ3fvGSmDp7xK1dNZfh6uGV_h-8NVlo3fXNoRNzI&m=awiDiMv0NtCLLz5-uNP7bpumXx_y47hSNPzjP1ztGHQ&s=ZAb7gDSyAGwhQGWD5e_OD-UJZa03v9DimjLmwivi2aM&e= 



-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.yale.edu/pipermail/nhcoll-l/attachments/20161018/5611b3a2/attachment.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: KotrbaEt2009.pdf
Type: application/pdf
Size: 47197 bytes
Desc: not available
Url : http://mailman.yale.edu/pipermail/nhcoll-l/attachments/20161018/5611b3a2/attachment.pdf