DCHAS-L Discussion List Archive
About This Archive | DCHAS-L 2025 Index | DCHAS-L Yearly Index | DCHAS-L Home Page
About This Archive
DCHAS-L 2025 Index
DCHAS-L Yearly Index
DCHAS-L Home Page
Next by Date
Subject:
[DCHAS-L] New Article
Date:
Apr 6, 2025 17:38 UTC
Author:
000006c59248530b-dmarc-request**At_Symbol_Here**LISTS.PRINCETON.EDU
From:
Neal Langerman <chemsaf**At_Symbol_Here**GMAIL.COM>
Subject:
Re: [DCHAS-L] A real-world question 04.04.2025
Date:
Apr 5, 2025 01:44 UTC
Reply-To:
chemsaf**At_Symbol_Here**gmail.com
Message-ID:
<CAOo07ZqTnMaMa+5pHsRdpWZRCqzMDViCgs+cjvbO=U9x57GOVA**At_Symbol_Here**mail.gmail.com>
In-Reply-To:
<1229307199.1572792.1743789944531**At_Symbol_Here**mail.yahoo.com>
We often use a calcium chloride solution for dust control. You want the pH above 9.5 to prevent HCN formation. Calcium hydroxide is not soluble enough. Perhaps a sodium hydroxide solution at about pH 9.5-10.0. Phenolphthalein or thymolphthalein could be used as an indicator. Ammonium hydroxide is too irritating. You will substitute 1 hazard for another.
You will need to control overspray and dispersion to prevent exposing your workers to the spray.
This is a tricky balance of HCN control versus worker exposure. Since it is outdoors, you might consider cyanide cartridges for the workers and then applying the caustic solution to the drummed or trucked dirt. Water or calcium chloride could be used on the open area for dust control.
You will want some real time monitoring for cyanide during the project.
NL
-----------------------------------------------------------------------------------------------------
NEAL LANGERMAN, PhD
+1 (619) 990-4908
Dear all: 04.04.2025
I am working with a team responsible for excavating soil where a plating facility used to exist ... before the fire. Sodium cyanide and potassium cyanide have both been identified in the soil.
Misting will be part of the dust-suppression protocol whenever the soil is disturbed. Since cyanides in an acid environment will evolve effective levels of hydrogen cyanide, I have required that the mist be treated with an alkali to maintain a pH of the water at a level high enough to preclude the formation of airborne hydrogen cyanide.
My questions are:
-- Would ammonia be an effective agent to raise the pH of the water to levels well above neutrality ... depending upon the concentration of ammonia added?
-- Is there a preferrred alkali additive?
-- Is there not a colorimetric pH indicator that could be added to the water to be able to provide a readily evident assurance that the water is maintaining its higher pH level?
I will appreciate every and all suggestions. I have a deadline of Monday, April 7, 2025 to submit my recommendations.
Nancy Carraway
626 676 7681
---
For more information about the DCHAS-L e-mail list, contact the Divisional membership chair at
membership**At_Symbol_Here**dchas.org
