Randy Holmes-Farley
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We are having a long discussion in a different thread about if and how Seachem Prime might detoxify ammonia.
I have never understood how the claimed ingredients in Prime (not clearly stated by Seachem, but probably close enough) would actually detoxify ammonia. I said that explicitly in an old ammonia article of mine, not doubting it could work, just not understanding.
In looking in more detail at known possible reactions for that thread, I have developed a hypothesis of how it may work. I wanted to detail it here as a stand alone thread since the other thread is very long and it could get lost in the shuffle there.
https://www.reef2reef.com/threads/does-prime-actually-detoxify-free-ammonia-nh3.849985/ (post #249 duplicates this post)
Here's a hypothesis that may be the reaction of Prime with ammonia based on known literature reactions and the exact composition claimed by Seachem. The product is NH2SO3-, a sulfamate. The reaction is analogous to the reaction with hydroxymethansulfonate, and according to one person writing about this years ago (Boomer), Prime was the Seachem way around the hydroxymethanesulfonate patents (I do not independently know that part)..
Here's the full justified rationale:
Seachem says Prime contains hydrosulfite salts and bisulfite. Hydrosulfite is a chemical synonym for dithionite. Seachem has been adament online that the product does not contain dithionite, despite them seemingly adding it. Why? Perhaps because it decomposes to trithionite as noted below, and trithionite is the actual active ingredient.
A mixture of sodium hydrosulfite (= sodium dithionite) and sodium bisulfite results in a variety of products, including trithionite:
"The decomposition of sodium dithionite in concentrated bisulphite buffer solutions follows first-order kinetics........Two sets of stable products, (½Na2S2O3+NaHSO3) and (Na2S3O6), found in ratios between 9 : 1 and 1 : 1, probably result from common intermediates in reaction (3)."
Note that Na2S3O6 is trithionite.
This reference shows that structure for the potassium salt:
Then this reference shows how trithionite reacts with ammonia in aqueous solution to form NH2SO3- (a sulfamate):
THE REACTIONS OF POLYTHIONATES: KINETICS OF THE CLEAVAGE OF TRITHIONATE ION IN AQUEOUS SOLUTIONS
"In the cleavage of trithionate in aqueous ammonia solutions, therefore, the following reaction is considered to proceed in parallel with reaction (1) described previously."
S306-- + 2NH3 = S203-- + SO3NH2- + NH4+
I have never understood how the claimed ingredients in Prime (not clearly stated by Seachem, but probably close enough) would actually detoxify ammonia. I said that explicitly in an old ammonia article of mine, not doubting it could work, just not understanding.
In looking in more detail at known possible reactions for that thread, I have developed a hypothesis of how it may work. I wanted to detail it here as a stand alone thread since the other thread is very long and it could get lost in the shuffle there.
https://www.reef2reef.com/threads/does-prime-actually-detoxify-free-ammonia-nh3.849985/ (post #249 duplicates this post)
Here's a hypothesis that may be the reaction of Prime with ammonia based on known literature reactions and the exact composition claimed by Seachem. The product is NH2SO3-, a sulfamate. The reaction is analogous to the reaction with hydroxymethansulfonate, and according to one person writing about this years ago (Boomer), Prime was the Seachem way around the hydroxymethanesulfonate patents (I do not independently know that part)..
Here's the full justified rationale:
Seachem says Prime contains hydrosulfite salts and bisulfite. Hydrosulfite is a chemical synonym for dithionite. Seachem has been adament online that the product does not contain dithionite, despite them seemingly adding it. Why? Perhaps because it decomposes to trithionite as noted below, and trithionite is the actual active ingredient.
A mixture of sodium hydrosulfite (= sodium dithionite) and sodium bisulfite results in a variety of products, including trithionite:
Chemistry of sodium dithionite. Part 1.—Kinetics of decomposition in aqueous bisulphite solutions
The decomposition of sodium dithionite in concentrated bisulphite buffer solutions follows first-order kinetics with an activation energy of 18 kcal/mole. The rate is also first order in bisulphite ion, variable fractional order in hydrogen ion and shows zero salt effect. The reaction...
pubs.rsc.org
"The decomposition of sodium dithionite in concentrated bisulphite buffer solutions follows first-order kinetics........Two sets of stable products, (½Na2S2O3+NaHSO3) and (Na2S3O6), found in ratios between 9 : 1 and 1 : 1, probably result from common intermediates in reaction (3)."
Note that Na2S3O6 is trithionite.
This reference shows that structure for the potassium salt:
Then this reference shows how trithionite reacts with ammonia in aqueous solution to form NH2SO3- (a sulfamate):
THE REACTIONS OF POLYTHIONATES: KINETICS OF THE CLEAVAGE OF TRITHIONATE ION IN AQUEOUS SOLUTIONS
The reactions of polythionates: Kinetic of the cleavage of trithionate ion in aqueous solutions
A kinetic study of the cleavage of trithionate has been made in water over the temperature range of 40–80°C, and in aqueous ammonia solutions over the…
www.sciencedirect.com
"In the cleavage of trithionate in aqueous ammonia solutions, therefore, the following reaction is considered to proceed in parallel with reaction (1) described previously."
S306-- + 2NH3 = S203-- + SO3NH2- + NH4+