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Subject:
Re: [DCHAS-L] Phenolphthalein or Replacement?
Date:
Nov 11, 2025 22:13 UTC
Author:
Pemberton, Drew (apemberton**At_Symbol_Here**uidaho.edu) <0000231dd2f469c4-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU>
From:
Jeffrey Lewin <jclewin**At_Symbol_Here**MTU.EDU>
Subject:
Re: [DCHAS-L] Phenolphthalein or Replacement?
Date:
Nov 11, 2025 21:28 UTC
Reply-To:
ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
Message-ID:
<CAEwQnqhAv9xTK-7CshF1BWVPHwf4irOQOjnAadqgZ65NiVV9VA**At_Symbol_Here**mail.gmail.com>
In-Reply-To:
<CAFCR6uZ38qew20uN1qVSmN10ZBmt-5H6bwX2iBMCzRXv-tkzpQ**At_Symbol_Here**mail.gmail.com>
When I checked a couple of SDSs for phenolphthalein solution they indicated they were mixed with ethanol and had a flashpoint below 60c, which makes the stock solution ignitable and a characteristic hazardous waste. Presumably you are diluting it as part of a reaction. If the alcohol is diluted to less than 24% it is no longer a characteristic hazardous waste (by definition) but may still be ignitable and prohibited by the sewer authority.
I found two different SDSs for bromothymol blue solution, one of which used IPA and, again, a flashpoint less than 60C.
But, even if you use an aqueous based dye you might still be not allowed to sewer it; some sewer authorities have prohibitions from dyes being sewered.
Hence, it should be collected for waste disposal, the question is does it meet the RCRA definition of a hazardous waste (EPA code D001) or is it collected and disposed of as a nonRCRA (Liquid Industrial Byproduct in MI) waste?
Jeff
Our School's EHS responded to a question that was brought up about phenolphthalein:
"I verified this with the wastewater district, and they confirmed that it [phenolphthalein] cannot be disposed of down the drain. I want to be cautious here if we start discharging materials improperly, it could trigger a wastewater audit and potentially open Pandora’s box for the college."
What do you all do? Are you still using phenolphthalein or have you replaced phenolphthalein with something like bromthymol blue or something similar? Do you get the same results or better?
or...
Are you still using phenolphthalein, if so how do you deal with the waste? If collecting the waste, is it worth the cost of disposal?
Warm regards,
David EldrEdge
Co-Owner
NALTIC Industrials, LLC
888.891.0077 Main
435.503.4972 Cell
435.767.7714 Google Voice & Text
435.654.2727 Fax
ᐧ
-- Jeff Lewin
Chemical Safety
Environmental Health and Safety
Office of the General Counsel
Michigan Technological University
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