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<p class="MsoNormal"><a name="_GoBack"></a>Reposting this from John Simmons on a similar question on the Natural History Collections Facebook page (because I couldn’t have said it better myself):<o:p></o:p></p>
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<p class="MsoNormal" style="background:#F0F2F5"><span style="font-size:11.5pt;font-family:"inherit",serif;color:#050505">What is recommended is a 1:9 mixture of formaldehyde and deionized water, buffered with two salts, which is to say, use 4.0 g of monobasic
sodium phosphate monohydrate plus 6.5 g of dibasic sodium phosphate anhydrate per 1 liter of a 1:9 mixture of formaldehyde and deionized water, which will yield a mixture with a pH of approximately 7.0, which is good. Tap water should not be used because its
pH varies widely from place to place and over the course of the year—to make reliable formaldehyde mixtures with tap water you need to test the pH of the tap water each time and adjust your buffering agent accordingly (and even then, you will not know what
buffers the tap water already contains from its processing, or if it is acidifying from chlorination, etc.). Distilled water tends to be too acidic and, in any case, its pH tends to be that of untreated tap water, which will most likely not be in a suitable
range. In the field it is usually impractical to use deionized water but carry a supply with you if possible.<o:p></o:p></span></p>
<p class="MsoNormal" style="background:#F0F2F5"><span style="font-size:11.5pt;font-family:"inherit",serif;color:#050505">Unbuffered formaldehyde is very acidic. The pH of full-strength formaldehyde is around 2.5 to 3.5 and when diluted 1:9 it will still be
around 3.0 to 4.6.<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Andy<o:p></o:p></p>
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<p class="MsoNormal"><span style="color:black">Andy Bentley<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Ichthyology Collection Manager<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">University of Kansas<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Biodiversity Institute<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Dyche Hall<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">1345 Jayhawk Boulevard<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Lawrence, KS, 66045-7561<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">USA<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Tel: (785) 864-3863<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Fax: (785) 864-5335 <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black">Email: <a href="mailto:abentley@ku.edu">abentley@ku.edu</a> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:black"><a href="http://ichthyology.biodiversity.ku.edu/">http://ichthyology.biodiversity.ku.edu</a><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">Nhcoll-l <nhcoll-l-bounces@mailman.yale.edu> on behalf of Esther Dondorp <esther.dondorp@naturalis.nl><br>
<b>Date: </b>Friday, February 12, 2021 at 3:27 AM<br>
<b>To: </b>"nhcoll-l@mailman.yale.edu" <nhcoll-l@mailman.yale.edu><br>
<b>Subject: </b>[Nhcoll-l] Question about buffered formalin, what buffer should I use?<o:p></o:p></span></p>
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<p class="MsoNormal">Dear colleagues, <o:p></o:p></p>
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<p class="MsoNormal">I need your advice on what buffer to use to fixate a large eel in formalin. I have to order 10% buffered formalin but I get the question from the chemical company what buffer they should add. The pH should be around 7 I guess?<br clear="all">
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<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Many thanks and best regards,</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Esther Dondorp</span>
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<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Senior Collectiebeheerder</span><o:p></o:p></p>
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<sub><span style="font-family:"Arial",sans-serif">+31717519313 - - </span></sub><o:p></o:p></p>
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<p class="MsoNormal"><sub><span style="font-family:"Arial",sans-serif"><a href="mailto:esther.dondorp@naturalis.nl" target="_blank">esther.dondorp@naturalis.nl</a> - <a href="https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.naturalis.nl%2F&data=04%7C01%7Cabentley%40ku.edu%7C9f0bd8bfe9f047f5c22b08d8cf387845%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C637487188763988014%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=PxOFtU4a7Pf%2B3zsWYin18T9dd9zsH2hYIKdf43uYebs%3D&reserved=0" target="_blank">www.naturalis.nl</a></span></sub><o:p></o:p></p>
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