# How to use Sodium Thiosulfate for fixing dicopper (I) tetraiodomercurate (II)?

DISCLAIMER

DO NOT TRY TO DEMERCURATE USING DESCRIBED PROCEDURE. CONSULT YOUR EMERGENCY SERVICE.

I found a discrepancy between a government-approved procedure of living quarters demercuration and the patent RU 2081198 C1 the procedure is based on.

The last phase of cleaning involves fixing remaining mercury salts $$\ce{HgI2}$$, $$\ce{Hg2I2}$$, $$\ce{Cu2Hg2I2}$$ (I didn't find any mentions of $$\ce{Cu2Hg2I2}$$ in literature), and $$\ce{Cu2[HgI4]}$$ using $$\ce{Na2S2O3}$$. According to the patent one should use acidified $$\ce{Na2S2O3}$$:

$$\ce{Na2S2O3} + 2\ce{H+} \rightarrow \ce{H2SO3} + \ce{S} + 2\ce{Na+}$$ $$\ce{mercury salts + S -> \ce{HgS} + other products}$$

However, the government-approved procedure suggests using not acidified $$\ce{Na2S2O3}$$ or $$\ce{HOOC-COOH}$$. I am wondering if it is a mistake. I found that $$\ce{HgI2}$$ is soluble in $$\ce{Na2S2O3}$$ in the Russian book on analytical mercury chemistry. So using $$\ce{Na2S2O3}$$ for $$\ce{HgI2}$$ removal makes sense.

My question

Is $$\ce{Cu2[HgI4]}$$ soluble in presence of $$\ce{Na2S2O3}$$ or $$\ce{HOOC-COOH}$$? Or are there other reactions that make it less dangerous or make $$\ce{Cu2[HgI4]}$$ easy to remove?

Reactions involved in demercuration according to the patent RU 2081198 C1

$$2\ce{CuSO4} + 4\ce{KI} \rightarrow \ce{Cu2I2} + \ce{I2} + 2\ce{K2SO4}$$ $$\ce{Hg} + \ce{I2} \rightarrow \ce{HgI2}$$ $$\ce{Hg} + 2\ce{KI} + \ce{I2} \rightarrow \ce{K2[HgI4]}$$ $$\ce{Hg} + \ce{Cu2I2} + \ce{I2} \rightarrow \ce{Cu2[HgI4]}$$ $$\ce{HgI2} + 2\ce{KI} \rightarrow \ce{K2[HgI4]}$$ $$\ce{K2[HgI4]} + \ce{Cu2I2} \rightarrow \ce{Cu2[HgI4]} + 2 \ce{KI}$$ Binding mercury wapors??? $$\ce{Hg} + \ce{Cu2I2} \rightarrow \ce{Cu2HgI2}$$

The method of demercuration from the patent RU 2081198 C1

Materials

1. $$\ce{CuSO4} \bullet \ce{H2O}$$ $$10\%$$ aqueous solution
2. $$\ce{KI}$$ $$10\%$$ aqueous solution
3. $$\ce{Na2S2O3}$$ $$25\%$$ aqueous solution
4. $$\ce{HOOC-COOH}$$ $$5\%$$ aqueous solution
5. sawdust (if a floor in demercurated room is made of material with many cracks, e.g. parquet)

Procedure

1. Remove visible mercury droplets
2. Spray copper sulfate until the floor is moistened
3. Spray double volume of potassium iodide over the floor
4. Wait for 10 days. Mercury droplets are located as red spots on the white layer of salts
5. Remove located mercury and salts from the floor
6. If the floor is made of material with many cracks, the floor is covered by a layer of sawdust impregnated by the mixture of $$\ce{CuSO4}$$ and $$\ce{KI}$$ and exposed for another 10 days. There may be several repeats of sawdust mercury absorption.
7. Fix remaining salts of mercury by the spraying of $$\ce{Na2SO3}$$ and then spraying of $$\ce{HOOC-COOH}$$.
8. Wait for 1 day
9. Wet cleaning.

The method of demercuration according to government-approved procedure

Materials

1. $$\ce{CuSO4} \bullet \ce{H2O}$$ $$10\%$$ aqueous solution
2. $$\ce{KI}$$ $$10\%$$ aqueous solution
3. $$\ce{Na2S2O3}$$ $$25\%$$ aqueous solution or $$\ce{HOOC-COOH}$$ $$3-5\%$$ aqueous solution

Procedure

1. Remove visible mercury droplets
2. Spray copper sulfate $$0.1 - 0.15 L/m^2$$
3. Wait for 2-3 minutes
4. Spray potassium iodide $$0.2 - 0.3 L/m^2$$
5. Wait for 1-3 days exposition for spilled mercury or 5-10 days if mercury is removed from the air
6. Remove mercury and salts
7. In rooms with the floor made of material that is not penetrable for mercury one turn of $$\ce{CuSO4}$$ and $$\ce{KI}$$ cleaning is enough
8. If the floor is made of parquet mercury droplets are removed from cracks using a flat knife
9. In living quarters, schools, and kindergartens remaining mercury salts are fixed using $$\ce{Na2S2O3}$$ or $$\ce{HOOC-COOH}$$ $$0.15 - 0.2 L/m^2$$.
10. Wait for 1 day
11. Wet cleaning

My question

Is $$\ce{Cu2[HgI4]}$$ soluble in presence of $$\ce{Na2S2O3}$$ or $$\ce{HOOC-COOH}$$? Or are there other reactions that make it less dangerous or make $$\ce{Cu2[HgI4]}$$ easy to remove?

Related questions:

• Could you add the actual question at the end? I am finding it hard to understand what it is that you are asking for.. Apr 12 at 14:14
• @SafdarFaisal Done. I have 4 questions. Should I make them separate posts? Apr 12 at 14:59
• Separate questions would be great. I was just about to ask if you could do that. Apr 12 at 15:06
• @SafdarFaisal I left 1 question is this post and created a new chemistry.stackexchange.com/questions/149855/… I'll create a question about $\ce{Cu2[HgI2]}$ and $\ce{HgI2}$ toxicity in 30 mins. Apr 12 at 16:04
• @SafdarFaisal question about toxicity chemistry.stackexchange.com/questions/149860/… Apr 12 at 17:13