Preparing Zinc Chloride

[Arthur Dent]

Hi,

 

Quick question about the preparation of Zinc Chloride... I have been attempting to prepare a small batch of ZnCl2 using zinc cut up in small strips and some HCl (25ml of 32% HCl and 25ml distilled water) in a becher.

 

Zn + 2 HCl → ZnCl2 + H2

 

This is my first attempt at this and at first, the reaction was quite energetic, so I figured that when it would subside, the acid would be neutralized and the result would (mostly) a pure zinc chloride solution.

 

But 24 hours after the beginning of the process, a strip of ph paper indicates that the content is still strongly acidic, even though the remaining little pieces of zinc have stopped bubbling.

 

Should I gently heat the solution to complete the process and get the ph down?

 

Knowing that ZnCl2 is very hygroscopic, is there any way to keep it in solid form, even if a bit "wet"? Will a glass bottle with a teflon seal be enough to keep the moisture to a minimum?

 

Thanks in advance for your input

[ercdndrs]

The solution is still acidic because all of the zinc touching the HCl has turned into Zinc Chloride.

 

Here's an analogy: say you have 20 nuts and 10 bolts. The nuts represent HCl, the bolts represent the zinc. Once you combine one nut and one bolt, that represents a zinc chloride. After you've combined all zinc with chlorine, the remaining HCl doesn't just disappear. It's still there, there's just nothing for it to react with.

 

Soo.. the result is that you can make more zinc chloride

[Arthur Dent]

Thanks for the info, that makes sense. I also read that pure zinc chloride solution is acidic (a 6M solution has a ph of 1!). I added a few thin strips of Zn to see it it would react and it doesn't, so I think i'm pretty close to a good solution of ZnCl2.

 

And after evaporation and dessication, I figure the remaining traces of HCL will evaporate too. My next task will be to filter out the solution first to get the tiny bits of undissolved zinc, zinc oxide and gunk. Then on to the hotplate!

 

- Robert

[Arthur Dent]

I just tested the dessication method using CaCl2 in the form of a household "damp-trap" box sealed in with an amount of Zinc Chloride solution sealed in a ziploc bag... The ZnCl2 won... after a full week in the bag, there is still 30 ml of solution and it hasn't dropped even 1 ml, it doesn't work at all.

 

Or am I too hasty? Anyway, I just took my becher with 50 ml of Copper Sulfate solution, who already has beautiful spiky crystals growing at the bottom and see if this damp-trap process will dessicate the solution faster. I'll use a hotplate to dry up the ZnCl2 instead.

 

- Robert

[Charlatan]

Hi,

 

Quick question about the preparation of Zinc Chloride... I have been attempting to prepare a small batch of ZnCl2 using zinc cut up in small strips and some HCl (25ml of 32% HCl and 25ml distilled water) in a becher.

 

Zn + 2 HCl → ZnCl2 + H2

 

This is my first attempt at this and at first, the reaction was quite energetic, so I figured that when it would subside, the acid would be neutralized and the result would (mostly) a pure zinc chloride solution.

 

But 24 hours after the beginning of the process, a strip of ph paper indicates that the content is still strongly acidic, even though the remaining little pieces of zinc have stopped bubbling.

 

Should I gently heat the solution to complete the process and get the ph down?

 

Knowing that ZnCl2 is very hygroscopic, is there any way to keep it in solid form, even if a bit "wet"? Will a glass bottle with a teflon seal be enough to keep the moisture to a minimum?

 

Thanks in advance for your input

 

Why are you making this stuff? Idle hands are the devil's playthings! Lucky for you I got the answers you need.

 

If you take this mixture, and want it to become solid, just throw some liquid Nitrogen into it. The nitrogen will evaporate inside it and you will be left with a solid you will. No need for a formula, all you need to do is throw the stuffies together and then 'cool it off'. Even more accessible is ice blox!

[Arthur Dent]

I will use Zinc Chloride to test for the presence of gold in solutions.

 

Thanks for your suggestion, however liquid nitrogen is not something I can easily access nor do I want to play with, even though I know of a distributor in my neighborhood. But maybe dry ice (CO2) would work?