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               Mercurous Chloride (Hg2Cl2) synthesis by AtomicDog
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Mercurous Chloride is a simple mercury salt with the form of Hg2Cl2. The
reaction described herin was thought to produce Mercuric Chloride (HgCl2)
instead, which is used for making amalgams. But it turns out that Mercurous
chloride does a perfectly fine job for amalgams and is thus a good substitute.
Hg2Cl2 is insoluble in alcohol and only slightly soluble in water but it still
manages to coat aluminum in a sol'n of either solvent. It is suggested that
Hg2Cl2 amalgams be made in mildly acidic water (pH 5-6) because it is at least
somewhat soluble in water and acidity increases that solubility. Apparently even
plain Hg in acidic water can work but Atomic feels that this is very difficult
to measure out plain mercury and thus get the same results. This reaction is
super easy and takes only a few hours at most.

On the plus side, Mercurous Chloride isn't quite as dangerous as HgCl2. That
insolubility makes it difficult for your body to absorb, the Merck even says
that if ingested, a saline laxative should be administered to prevent mercury
poisoning, try that with HgCl2! (joking, don't try that). Hg2Cl2 is a white,
odorless, tasteless powder. Protect it from sunlight or it will slowly degrade
into HgCl2 and Hg. Hg2Cl2 sublimes at 400-500C without melting. Please note that
any solution of mercury should be considered EXTREMELY dangerous and poisonous
and be handled using vynal gloves with extreme care.

We'll be making Hg2Cl2 today by passing chlorine gas over elemental mercury at
room temperature and pressure. You'll need elemental mercury from an old
thermometer or thermostat, and muriatic acid (31.5% HCl), and sodium
hypochlorite sol'n (Clorox bleach). Atomic has found that a 2:1 ratio of bleach
to acid is about right or you could use liquid chlorine (stronger stuff) from
the same pool store you got the acid at go 1:1. Chlorine gas is a nasty green
gas that will drive you out of the lab in very small amounts and is so corrosive
that in time it will turn steel into dust. You don't want any leaks in your
setup for gas to escape! 200ml of acid and 400ml of bleach will give you 15-20
min of gas and that should do it for you. In an ideal setup, your Sodium
Hypochorite sol'n drips from an addition funnel into a flask filled with your
acid and is stirring away. If you don't have mag stirring then you'll have to
swirl the flask occasionally to get everything to react. A tube leads the gas to
another where it bubbles through water to clean the gas and then another filled
with CaCl2 to dry it, and then to another where the mercury waits. Atomics
experience is that the water and drying aren't really necessary because not much
else will react with the Hg and since Hg2Cl2 isn't really H2O soluble or
nightmarishly dangerous that drying the gas is no big either. But be warned! The
best way to go is clean and dry.  If you use water to clean the gas be aware
that for a few minutes it will absorb your gas until it becomes saturated and
lets it pass through, be patient. When the green gas does hit the mercury you'll
se it right away: Your fast moving, T2 looking blob will turn a dull dark gray
instantly and slow down or freeze up entirely. This is a hard layer of Hg2Cl2
forming on the outside of your mercury, protecting it from the gas all around
it. You have too pick up the flask and shake that baby to break out the Hg
inside and spread it all around the flask so it can react, expect to be doing a
lot of this. 

And try to use only as much Hg as you think will coat your flask or you'll have
a hard time getting it all to react. At this point Atomic should point out how
nice it is to use surgical tubing for this reaction instead of regular chem
tubing. Surgical tubing is very flexible and allows you to really pick-up and
shake that flask without pulling your setup apart. Once you have that stuff
spread all around it will probably be dark grey with white at any tips. If you
can see that the flask is full of green chlorine gas then you can stop the gas
for now and wait. You need to wait for the mercury to react, you'll be done when
it's almost completely white and even looks reacted from underneath. You'll
probably never get it 100% reacted unless you take the flask out of the setup
(hold your breath!) and use a spatula to 'scratch' around in there and break-up
any remaining clumps and unreacted patches. This is especially true if you use
too much Hg for the size flask you're using. Once finished you can use that
spatula to scrap out all you can and put it in a suitable container. Then pour
some water in the flask and swirl that baby to lift the remaining Hg2Cl2 off the
flask walls and quickly pour it into a Pyrex dish. When the water evaporates you
can scoop the rest of your Hg2Cl2 into your container.

There you have it, the new and improved doc, now go forth and bee fruitful!



