View Full Version : How did I get hydrogen sulfide?

Antti Aalto
23-Jul-2005, 12:33
Hi,I've just tried out the DS-12 film developer formula by Ryuji Suzuki at http://silvergrain.org/Photo-Tech/film-dev-recommend.html . It seems hydrogen sulfide was formed at two stages and I'd like to know why. I've got a clue, but I just want confirmation and some assessment of the risks if you can. For reference, the formula goes:
metol 0,4 gascorbic acid 1,0 gsodium sulfite 20 gsalicylic acid 0,2 gtriethanolamine 2 mlsodium carbonate 2,0 g and water to 1 litre. What I made was three litres of developer starting with about 0,2 litres initial dissolving volume, just tap water. Of course it didn't all go into the initial 0,2 litres, so it was more like immersed for sodium sulfite. So three times the amounts above in three litres (if any of this counts). The thing I did wrong was to dissolve metol only after ascorbic acid, because this was my first time with the home scale and fume cupboard so I thought it would be safer to check the scale this way. I think I got the rotten egg smell, which I now take was hydrogen sulfide, after I added metol to the mix.
Since I did this in a fume cupboard there was little smell, but it smelled outside the house when I left the room, so maybe there was much more blown out in the exhaust. The second time the smell appeared was in the toiler-for-a-darkroom when I dipped my gloved hands in the same washing bucket after immersing them in both the developer and the fixer (Ilford Hypam).I just checked the metol I was provided with and realised that it's of the p-Methylaminophenol sulfate-variety. Is the variety referred to in the formula supposed to be plain metol? I'm a bit poor at chemistry, but the way I see it, sodium sulfite's there to provide alkalinity, but can it be said that the sulphur in sodium sulfite is more stable than the one in the metol I got? It's bound to three oxygens instead of the four in the metol. Would this mean there's little or no risk of hetting hydrogen sulfide with the DS-12 formula as such if the metol's sulphur free? I'd say this is the case, but I'm no chemist and I don't know how marked the difference im the sulphur compound stabilities is here and how much hydrogen sulfide I might get? I read that the nose is highly sensitive for H2S, but then again nose does adapt, the toxic amounts are very low and I don't have room to faint anywhere but ON the chemicals.The CAS number for the metol I got is 55-55-0, whereas plain metol has the number 150-75-4 (searched ChemId). The MSDS I got for the 55-55-0 -stuff has "information not available" in the stability/reactivity field, but the English version found on www.acros.com (the provider) says about hazardous decomposition products : Oxides of sulfur, sodium oxide and not compatible with acids. To return to my main question: Does the DS-12 normally generate hydrogen sulfide when combined with acids? Sorry for lack of coherence above, but if I really had a very specific idea, I wouldn't have to ask. Cheers! Antti

Donald Qualls
23-Jul-2005, 13:16
Hydrogen sulfide evolves when sulfite comes in contact with acids. One source is when sulfite bearing developer is carried over into an acid stop bath, though commercial acid fixers contain sulfite in an acidic solution and evolve some hydrogen sulfide at all times. In mixing as you did, with incompletely dissolved sulfite (a weak alkali), the (slightly acidic) metol or the salicylic acid may have cause evolution of H2S before the TEA and carbonate could alkalize the solution. You should mix each ingredient until completely dissolved before adding the next.

BTW, if you get enough hydrogen sulfide built up to faint, you'll die. The stuff is heavier than air, and when you fall on the floor, you're hitting the highest concentration. However, if your darkroom is ventilated it shouldn't be that big a problem; the usual issue is that people get lung irritations that mimic asthma from prolonged exposure at low levels. If your darkroom isn't ventilated, change it so it is.

Paul Coppin
23-Jul-2005, 14:31
H2S is also flammable, in addition to being poisonous...

Ole Tjugen
23-Jul-2005, 14:40
As long as you can smell it, H2S isn't all that bad. The nose shuts down in protest long before you reach fatal concentrations!

Mike Gudzinowicz
23-Jul-2005, 16:05
"Metol" is the sulfuric acid salt of p-methylaminophenol. It will not generate

hydrogen sulfide.

The "sulfur" odor isn't hydrogen sulfide - it's sulfur dioxide (SO2) which

is formed from sulfite under acidic conditions.

SO3-- + 2 H3O+ -> H2SO3 + 2 H2O

H2SO3 -> SO2(g) + H2O

Any hydrogen sulfide formed in an alkaline sulfite solution will react with

sulfite to form thiosulfate (hypo).

It is very likely that you could avoid this sort of problem by following the

usual practice of dissolving chemicals in water with a volume of at least 75%

of the final solution volume (750 ml+ for 1 liter).

I don't use that developer.

23-Jul-2005, 18:05
Maybe THAT's what the smell is in my darkroom after I've been standing at the sink for a few hours. And all the time I thought it had something to do with my diet and digestive tract.

Jorge Gasteazoro
23-Jul-2005, 18:18
Maybe THAT's what the smell is in my darkroom after I've been standing at the sink for a few hours. And all the time I thought it had something to do with my diet and digestive tract.

Could be, could be Bill. It all depends whether you had beans or not before the DR session... :-)

23-Jul-2005, 20:38
Jorge, it's a Leica enlarger so schnitzel and Sauerkraut....

Antti Aalto
8-Aug-2005, 03:05
Closing the thread so it won't make anyone doubt the DS-12 formula. Apparently it is the fume cupboard that brought hydrogen sulphide up the drain. I've tried out mixing the developer several times and there's no gas formation whatsoever to be seen. As a reminder, I didn't see the gas form in the developer in the first place, I just smelled it. Lacking a pH meter or indicator slips this is only a guess and I don't know if the pH change was buffered or not (and didn't bother to solve it), but I added 10% acetic acid to about 1/3 the volume to simulate a lower pH due to incomplete dissolving of alkalising constituents in the mixing. This didn't release detectable hydrogen sulphide, so all in all I'd say the problem I postulated above isn't real.Also Mr. Suzuki kindly replied that rather great energy would be needed to have H2S form.I've learned that the fume cupboard was installed without considering how to bring in adequate replacement air so it's brought in from the sewage system. Obviously this is something that has to be fixed as there is no knowing how much H2S can be released into the room this way and how rapidly the levels can change.