Mercuric Chloride Synth Problems

[Potential]

OK, I am at the end of my rope...I have done the HgCl2 synth (per Rhodiums site) once and have not been able to repeat it!  I have no idea what I keep screwing up...so here goes:
1. 20g of Hg and 60ml of H2SO4 in a flat bottom flask
2. Contents of flask are heated and things get bubbly
3. HgSO4 is produced
4. Solution is allowed to cool and excess acid is poured off.  HgSO4 crystals are dumped into 750ml of hot water.
5. The crystals turn bright yellow in the hot water.
6. The solution is filtered (While still warm?).
Now, should any of the yellow crystals come through the filter?  Should the filtered solution be clear or have a yellow tint?

This is where I think I am screwing up but I am not sure.  It is driving me crazy...I've done the Benzo Wacker and MM's Nitro Al/Hg but am getting stopped cold by that damned Hg reaction...

I know there is more to the synth and I realize pH is important during the last evaporization of the water (I've been using pH test strips just to make sure I wasn't way off).

[Tdurden969]

Why not make HgI2  or Hg2Cl2?

Much safer (for you) and easier to make.

Both  amalgamate pretty much the same as HgCl2 - just takes a little longer.

[hypo]

> Now, should any of the yellow crystals come through the filter?
> Should the filtered solution be clear or have a yellow tint?

what is your problem here? iirc, the solution stays yellow and of
course the crystalls stay in the filter paper.

iirc, the only tricky thing is to not over acidify in the end.

(i always thought this filtering step is quite wasteful. the yellow
crystalls are a mercury salt, maybe one could add those to the next
reaction?)

[yinga]

Here's another (and IMO better, although I haven't tried it) synth for HgCl2 from

http://www.sciencemadness.org/talk/viewthread.php?tid=706&page=2

:

Mercury salts aren't as precious as they're made out to be. It was easy to prepare HgCl2 by stirring rapidly (with a magnetic stirrer) with an excess of 27.5% H2O2 and 38% HCl, then boiling to remove remaining H2O2 and HCl, and then crystallizing. 

[Potential]

Alright...
I just took another crack at the HgCl2 synth and ended up with a pile of bright yellow crap...

Here's what I did:
1. heated the H2SO4 and Hg until it bubbled
2. let it do so until all Hg was converted to HgSO4
3. let it cool
4. poured off the excess acid
5. dumped into 700ml of hot dH2O
6. filtered...filtered liquid was clear this time (I hadn't been using fine enough filter paper)
7. added sat. bicarb solution
8. it fizzled...I kept adding it...after some addition, it turned yellow, then it a red/brown precipitate formed
9. solution was filtered and red/brown/yellow stuff was left on filter paper
10. the filtrate was washed with dH20 then mixed with 20ml of dH20 to form a suspension.
11. the HCl solution was made with 31.45% HCl
12. it was dripped in the suspension...after some time, it started to turn yellow
13. when I thought I saw some white precipitate (how obvious is the appearance of this white precipitate?), I stopped the addition of HCl solution.
14 I put it on the hotplate and boiled off the excess water then filtered...

Result:  one pile of fine bright yellow powder!  What in God's name am I doing wrong???

[Potential]

So, the pile of bright yellow crystals dried to a lighter, pale yellow overnight...just for shits and giggles, I put a bit of the yellow crystals in a flask with some methanol and some ground Aluminum bits.  After a couple of minutes, the tiny bubbles started to rise...

I'm guessing there must be some mercury salt in that yellow crystal pile that is causing the aluminum to amalgamate.  Is there a way to purify/separate what I want from the yellow pile of crystals or would they suffice to be used in the Nitro Al/Hg reaction???

[hypo]

the yellow stuff _is_ a mercury salt. maybe some
mercury hydroxide or something. just use as is.

[yinga]

The yellow is probably still HgO.  I would add more HCl to convert it to the desired product.

[alphacentauri]

The yellow is not HgO, it's HgSO4. I know this because I use mercury sulphate to block Cl ions as a mercury sulphate complex to prevent Cl oxidation in the COD determination of waste waters. I buy sometimes lab grade mercury sulphate: it's a white cristalline heavy powder, very poisonous and expensive, and when you add water to it, it becomes yellow.

[yinga]

Post 266873

(Mountain_Girl: "Embellishment of Zygoat's HgCl2 synth", Methods Discourse)