Talk:Sodium sulfite

message: I have conflicting data on the temperature at which the heptahydrate loses water. Lange's gives 33.4°C, which seems reasonable for a substance that effloresces at room temperature. 44th CRC gives 150°C, but I expect that this is in an atmosphere of pure steam. In reality there are two variables controlling whether heptahydrate loses water. One is temperature and the other is the ambient vapor pressure of water. Karlhahn 03:22, 23 August 2006 (UTC)
thread_title: Heptahydrate

message: Is this a safe food additive?
Teresa Harnden, MS, RD  —Preceding unsigned comment added by 153.48.52.241 (talk) 23:54, 5 May 2008 (UTC)
thread_title:  NaSo3 as a food additive? 

message: H2SO3 does not exist in solution.  As far as I know, it is not commonly found at all.
My old 3rd Ed. Cotton and Wilkinson (Advanced Inorganic Chemistry) claims it is not known (pg 447).  Certainly, if the free acid was not known in 1972 then this is NOT at all likely to be a preparative reaction in the lab.  I believe it is nonsense.  Comments?  This article cites a 1976 Merck Index as its only source.  This is laughable.  The Index is a compilation of older sources and can certainly NOT be relied on for this type of information.  I am going to change the article and remove the questionable part.  Here it is, in case someone who actually is knowledgeable about this knows I'm wrong.
{
reacting sodium carbonate with sulfurous acid:
:Na2CO3 + H2SO3 → Na2SO3 + CO2 + H2O
The second way of prepare it in lab is 
}
173.189.74.87 (talk) 19:37, 1 October 2012 (UTC)
replies: text: Most recent C&W says, that it does not exist per se, but that a hydrated sulfur dioxide does exist.  Therefore, the reaction should be H2O + SO2 + NaCO3 gives the products shown.JSR (talk) 19:56, 1 October 2012 (UTC)
replies: text: So that means that you difinively exclude all acidic gaseous oxides from being converted to acids in water? Carbonic acid is a weaker elecrophile and it exists in water as both Carbon Dioxide and Carbonic acid, a very well known equilibria (crucial in Medical science). Being a stronger electrophile the expectation is SO2 would react more completely with water molecules to make sulfurous acid. Fascinating that articles like http://www.ncbi.nlm.nih.gov/pubmed/12212735 find ample HOSO2- in SO2/water solutions. And solutions of Sulfur Dioxide in Water have a pH of 2 so assume 1% HSO3- versus H+. http://pubs.rsc.org/en/content/articlelanding/2014/dt/c3dt52890a#!divAbstract shows equilibrium concentration H2SO3 at pH 2.
Shjacks45 (talk) 20:16, 5 April 2014 (UTC)
thread_title:  I believe this is wrong. 

message: In reducing Silver Halide to Silver the Developer, typically Hydroquinone (or para- methylaminophenol, Metol) is oxidized to Quinone. Sulfite adds to the activated double bond of Quinone to make Hydroquinone Sulfonate. Sulfite (Bisulfite for non-acidic compounds) adds to a wide variety of double bonds from Resorcinol to Oleic Acid. The purpose of "Hypo clear" is to remove chemicals that can react with the Silver photograph image: Thiosulfate lowers Silver's EMF allowing it to be air oxidized and Thiosulfate decomposes (acidic solution, another purpose of washing is to remove acidity from the "Fixer") to Sulfur which attacks (bleaches) the photo image . Sodium sulfite does form complexes with metals and is used as cyanide replacement in Gold (and Silver) plating. Washing with sulfite in addition to leaving harmful salts on the filmstock would also cause long term deterioration of the film image. Shjacks45 (talk) 17:59, 5 April 2014 (UTC)
thread_title:  Photo Developer reference wrong.