H2SO4 + NaCl Products, end point and how to find it?

[Larrystein]

Hi, this is my first post on the forum. So firstly, Hello. I am a late bloomer, in the science community, being 44 and father of two (just about)adults.

 

Secondly, as per the title. I have searched for but not found an answer. How can I tell when the end point or AN end point has been reached? I have read that the end point is reached when no more HCl(g) evolves. However, with the amount of reflux that happens how can you tell if the gas has stopped evolving? Or is the end point when the reflux starts?

 

I perhaps should say WHY I want to make HCl(aq). Well I cannot go out to a supplier as my disability means I cannot walk far or drive any more. I also cannot find a supplier willing to sell and post in small amounts, unadulterated quality, to experimenters. Possibly because of what it can be used to make? I was able to buy only H2SO4 in 38% Max or battery acid. So, the reaction is fairly slow in starting and I have to apply 185-190°C in my sand bath.

 

I have made two macro scale attempts at making HCl(aq). The first attempt the products were a yellow sol and HCl(g). From what I have been able to find on Google, that is what is supposed to happen. The HCl(g) was bubbled through DD H2O giving HCl(aq). I particularly like to watch the formation of the bubbles and them dissolving in the H2O before they can reach the surface . It seems to have made a fairly strong HCl sol. I tested it with a 5mm square piece of Al foil, which was fully dissociated after 2 mins.

The yellow sol I also tested with the Al foil, It dissolved in 3mins. However, I was not happy about the reflux towards the end of the experiment. I don't think any HCl(aq) was drawn into the reaction vessel but it could have?

 

So, with the second attempt I stopped as soon as the reflux activity started but ended up with a colourless product in the reaction vessel. This colourless sol dissolved the Al foil in less than one min! Have I just concentrated the H2SO4, have I stopped before the yellow product developed, not enough heat, too much heat or have I contaminated my experiment some how?

For the second experiment, the cooled HCl(aq) from the first reaction was used to absorb the HCl(g) from the second to give me a stronger concentration of HCl(aq).

The resultant HCl(aq) is indeed much stronger than before the second experiment. It dissolved the foil in less than 30 secs.

 

If it's a bit hard to follow my discription of the experiment. Ask me for clarification. I know there are a lot of questions in this post but I really want to understand what is happening in this experiment and why I had two different outcomes.

 

 

Any help please.

 

Larry

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I just realised you might wonder why I want HCl(aq) in the first place.

Well, I have no intention of making any narcotic drugs or psychotropic substances that's for sure. Nor indeed any other illicit experiments.

I have purchased A big chemistry set to do some learning. As I am recently divorced and housebound, I wanted something constructive to do with my time. Naturally it requires some HCl(aq) for some of the more interesting experiments. Which again Naturally are not included in the kit.

 

Thanks for any help.

 

Larry

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By the way: I used the same volume of H2SO4 in both experiments. However, I think I used more NaCl in the second as there was some NaCl remaining at the end and I don't have a reliable balance.

I know, I know, measure everything and record mass/volume/molarity. But I don't have a balance so cannot.

 

Any help Please!

 

Larry

[John Cuthber]

Hi

What aparatus do you have?

If you have a still (or the bits to make one) then (1) you are probably in breach of the law in many countries but

(2) you are well placed to make HCl.

You can distil a solution of HCl from a mixture of NaCl, H2SO4 and water (be careful mixing them).

Also, if you plan on doing much chemistry you should think about getting a balance- it makes things so much easier.

For reasons that I don't understand there are lots of blances on ebay marketed for people who want to measure "herbs". I'm not that fussy when I put a sprig of parsley on the fish before I serve it but I guess some people want to add exactly the right amount of mint to their sauce.

Whatever their reasons, there must be lots of them because they have established a market. I don't mind because it means that I can buy a half-decent balance for not a vast amount of money. I bought mine in an electronics shop and paid cash so if anyone is setting up a database of "People who worry to much about the weight of 'herbs' " I'm not on it.

I understand that it's difficult for you to get out to buy stuff but a lot of things are up for sale on eBay so you might want to look there.

[Larrystein]

I have made my own wine and sometimes beer in the past. And yes! I do have a home-made pot still. But, and this is important to understand, I would never distil any alcohol with it. It's far too dangerous to DIY alcohol. I made it for distilling water and only water. It is not a column still or fraction still it is a plain pot and coil still.

I only have a need for double distilled H2O and because of my painkillers I cannot partake of high alcohol liquor even if I wanted to.

 

Surely, if it was illegal to own a still or the parts to make said still. Wouldn't then every chemistry labs in the country be in breach of said laws?

 

Here in the UK, it is not illegal to run a still for the distillation of H2O. It is illegal to distil alcohol for human consumption. Well, I say illegal, but actually it is not illegal to do, just illegal to do without paying "Her Majesties Revenue & Customs" excise duty and registering your premises as a producer. There are lots of other regulations that you have to follow also.

Strangely, You can circumvent most of these laws if you are producing in small amounts for scientific or manufacturing purposes and can prove you cannot use denatured alcohol in your process. However, you must get consent from "Her Majesties Revenue & Customs" before hand. I have also read, on a biodiesel website, that for making Biodiesel you can distil your own ethyl alcohol(2.5lt max) However, I could not find this "Law" on HMRC site so don't know how lawful this really is.

 

I do have a kitchen scale that is fairly accurate(.5g) but no way of testing it. so, could not tell if it is truly accurate. But didn't bother to use it in this instance anyway.

 

If I didn't know about Ebay I would probably be one of a very few people in the world who don't. I have been looking at the balances on there but haven't had the balance (please excuse the pun) to afford it just now.

 

Lastly, I think when "people" need a balance to weigh "Herbs" they are weighing it prior to putting it into small zip-lock baggies for illegal retail, not for making Pot-pourri!

 

Thanks

 

Larry

[John Cuthber]

HM customs will assume that any still is used for alcohol and ask why it's not licensed. They don't care about science.

Most labs should have a license but don't bother.

Anyway, what do you know about azeotropes?

http://en.wikipedia.org/wiki/Azeotrope

 

if you have a mixture of water an HCl that's about 20.2% HCl by weight and distill it it will come over as 20.2% but if you start with a lower concentration then water distills over first then you get the azeotropic mix (about 20%).

Similarly, if you start with more than 20.2% then HCl gas will come over first (and fill up your room) until the concentration in the pot falls to 20.2% then that mixture will distill.

It's a bit more complicated if there's other stuff present but I'm fairly sure that if you make a mixture of H2SO4, NaCl and H2O that's equivalent to a little under 20% HCl and distill it you will get nice clean 20% HCl

Do you know how to calculate the proportions needed?

[Larrystein]

I guess that was my point, I know very little about azeotropes.

Are you saying HCl(aq) has an azeotrope constant of 20%?

What I mean is that at or over 20%, water then HCl will distil out of the solution. Below 20%, just the HCl distils, until we reach 20%, then water will come with it? I think that's how I understood what you said.

 

Proportions? You mean molarity? yes I do know how to calculate molarity and do titration. I just wasn't concerned about the product except the HCl(g) at the time. I am going to do it again only properly next time. With proper recording and measurements.

 

(and fill up your room) You forgot to mention KILL ME if I don't absorb and use a fume hood.

 

 

Anyway, can you shed any light on my main questions from my original post? What is the product and how to tell when the end point is reached? I know it should be Sodium Sulphate. Why have I ended up with two different products one colourless and one yellow?

 

Thanks

 

Larry

[John Cuthber]

You seem to have got the bit abnout the azeotropes and the British art of understatement.

 

The yellow colour is probably due to some trash in the acid. Iron compouinds in HCl give yellow colours and so do sugars (that means paper ad cotton dust from a towel as well as the stuff you put in the tea).

For the simple version of adding acid to salt and heating it you know the reactions over when the stuff stops giving off gas. Sometimes you can see this and sometimes it's basicly a judgement call. In this case, when there's no more gas being given off, the stuff will try to suck back into the gas generator (and you really don't want that.)

 

It's not entirely a joke when that say chemsitry is as much an art as a science.

[Larrystein]

Right, I understand now.

 

Thanks for your help.

 

Larry