HOKE PAGE 44

[INDY864]

I am removing nitric acid by Hoke's method of evaporating and treating with HCL. Once I concentrated the A/R to a syrup and then added HCL, the product changed from a dark yellowish brown solution to a light yellowish brown solution with precipitation. Hoke says the precipitant is possibly silver. The solution is far more cloudy than before. And I haven't raised the ph much after the first evaporation.

I realize I could use urea. I also realize I could add several flakes of gold. I just wanted to learn all I could and reach neutral ph the old way and learn about how things react. Should I just keep the evaporation/add HCL cycle going until I get the ph to neutral?

 

[Anonymous]

I just wanted to learn all I could and reach neutral ph the old way and learn about how things react. Should I just keep the evaporation/add HCL cycle going until I get the ph to neutral?

This process has nothing to do with neutralizing the PH. It is designed to remove the nitrates in the solution.

 

[Harold_V]

What mic said.

When you add HCl, it's normal for a (white) precipitate to form, and it's normal for the color to shift (you've diluted the solution). Key to knowing when you have eliminated the free nitric is when, upon addition of free HCl, you do NOT get any brown fumes from the solution. It should have been evaporated until it was quite thick---syrupy, before adding the HCl. Added too soon, there is no reduction of free nitric.

I endorse your effort to learn the basics. Having a firm understanding will permit you to make decisions in the future. Those that explore for reasons other than laziness often miss the boat, because they have no clue about what is to be expected. How does one improve anything when they have no clue at the outset?

Harold

 

[NoIdea]

Evening – I try to, when dealing with new procedures process, start small, get a feel for what happens at what time and under what condition.

I don’t ever recall something I have build or process tried, for it to work exactly the way it played out in my mind, sometimes not even close. Be Safe.

Just keep reading and trying, until you are happy with the result, then and only then do you move on to bigger things. Practice make perfect. Oh, don’t forget patients, and lots of it. It’s a virtue this forum has been teaching me. Be Safe.

Take/Make notes and photo’s.

Nothing worse than ending up, at the end of a hard working day, with a bucket of Yuck. OK, two buckets of Yuck :roll:

Just my two cents worth

Enjoy your evening

Cheers

Deano

 

[p13t_chan]

Key to knowing when you have eliminated the free nitric is when, upon addition of free HCl, you do NOT get any brown fumes from the solution.
Harold

How if nitric was no eliminated well then i put HCl,is syrup change be AR??can it reprecipitated?

 

[NoIdea]

Key to knowing when you have eliminated the free nitric is when, upon addition of free HCl, you do NOT get any brown fumes from the solution.
Harold

How if nitric was no eliminated well then i put HCl,is syrup change be AR??can it reprecipitated?

Hi p13t_chan, The nitrates are in the form of salts, or free nitric acid if you used too much, adding HCl will displace the more volitile nitrates, producing NOx gas and the more stable chlorides, and any nitric acid will tend to evapouate off first(lower boiling point), as well as a little HCl.

When using Poor Mans AR sodium chloride is one of the resulting salts in soulution along with your gold chloride.

Deano

 

[INDY864]

Thanks Guys, and especially for the support,
Don't I have to reach a neutral ph before I add precipitant?

 

[INDY864]

Guys, adding to my last question, I know better than to assume. I'm suppose to be an engineer. :lol: I just thought a neutral ph would result from the nitric releasing, and the HCL breaking down from the heat. Harold, I did get the solution to a VERY thick syrup and I did get a NOx release. Mic, I will use your suggest a few months ago to drop a flake of gold to use up the nitric the next trial. I will see the settling at my shop tomorrow. Since I used real A/R I will assume any gold is still in solution and not in the precipitated salt. But I'm not going to throw it away. i've read the first 150 pages of HOKE about 10 times and I'm taking experiments slowly. So clue me in on the PH.
INDY

 

[gold4mike]

Since you did get a release of nitric fumes when you added the HCl you'll want to repeat the process. Do this until you no longer see the red/brown fumes.

When you're done you will have just added HCl so, no, your solution won't be neutral. At this point I double the volume with water, precipitate, then continue with washing the resultant powder, etc.

 

[INDY864]

Thanks Man,
Just thought the heat would get rid of the HCL.
INDY

 

[samuel-a]

Hi INDY864

I think the confusion came from the use of the word "neutralizing", where in our case is in a sense of neutralizing the AR but not acidity.

I fact, your AuCl3 was previously dissolved in HCl to give Chloroauric acid (HAuCl4), with it in the solution will be some other metals chlorides, free nitric acid, and some dissolved NO3 salts of metals... the evaporation process convert them to chloride salts, releasing NOx gas in the process.

 

[Harold_V]

Thanks Guys, and especially for the support,
Don't I have to reach a neutral ph before I add precipitant?

No! Nor should you. The solution should be acidic. I kept mine near 1 pH intentionally, by the addition of free HCl, which does no harm aside from destroying filters on occasion.

All it takes to precipitate almost everything in solution is to change pH from acidic to basic. If you attempt to achieve neutral pH, you risk precipitating things that should stay in solution.

Harold

 

[INDY864]

Thanks Harold