DIY Alkatronic reagent

[dwest]

According to @dwest 50ml of 1M sulfuric will make 5 liters of reagent.

If correct then, 10ml of 1M sulfuric will mix with 990ml of rodi.

I think the confusion might be from the fact that when you buy alkatronic reagent (at least in the past), it was 0.1N. You had to dilute to 0.02N to use it.

 

[Kershaw]

I think the confusion might be from the fact that when you buy alkatronic reagent (at least in the past), it was 0.1N. You had to dilute to 0.02N to use it.

I read through all the pages of this thread. And there seemed be inconsistent information. But I am far from a chemist and am just looking for a recipe that will work with what I bought. I need easy math lol.

 

[dwest]

I read through all the pages of this thread. And there seemed be inconsistent information. But I am far from a chemist and am just looking for a recipe that will work with what I bought. I need easy math lol.

If I were making it, I would use 10 ml of your 1M (2N) sulfuric acid and 990 ml water.

 

[Kershaw]

If I were making it, I would use 10 ml of your 1M (2N) sulfuric acid and 990 ml water.

I’ll try that. Just realized I need to order the small tubing for the alkatronic. Thank you!

 

[Asthix]

Oh oh. I was just reviewing this thread because I am again facing the prospect of coming up with a DIY replacement for the OEM reagent. The 4L of Coralvue reagent that I was able to purchase for $70.49 is now $154.00 since Coralvue stopped selling their version and my LFS can only get the BRS version.

I did work out the required dilution factor (1:99) a couple of years ago for a 20 baume 4L bottle of muriatic acid I have on hand, but your comment was years before that, and I am now wondering if this means that the 4L bottle would have become less concentrated in the meantime. If so, this would negate the possibility of using it as a suitable replacement for the OEM.

@Randy Holmes-Farley can you comment on the accuracy that muriatic acid will diffuse through the PET bottles it comes in?

Didn't know about that but i'm using my DIY Reagent for the last 4 years with no issue at all.
I make 5L batch that got used in about 6 month with not much difference from beginning/end.
I'm curious where you got this information, maybe with our/store concentration that's not an issue.

 

[Dennis Cartier]

Muriatic acid doesnt work because it evaporates to the air. It also diffuses through the walls of a pet bottle.
For a onetime measurement its good. Sulfuric acid does not evaporate in low concentration. 98% leaves a smoke that will damage Your lungs. If the air humidity is low spill will become more concentrated and cause rust on metal.
I would use citric acid. Does not evaporate or interact with air humidity. But of coarse the water its solved in can evaporate if kept open.
I would use drip bags as in a hospital to minimize the evaporation.

Didn't know about that but i'm using my DIY Reagent for the last 4 years with no issue at all.
I make 5L batch that got used in about 6 month with not much difference from beginning/end.
I'm curious where you got this information, maybe with our/store concentration that's not an issue.

The post that led me to pose the question is quoted above. Hopefully Randy will shed some light on the veracity of the statement.

 

[Randy Holmes-Farley]

I’m addressing the top quote? It does have several statements that I think are untrue or misleading.

Citric acid does not seem at all suitable for doing seawater alkalinity titrations. Alk titrations are usually done with a strong acid. That is, an acid (HA) where at any pH attained in the titration, all if it is in the ionized state, H+ and A-. Citric acid is a weak acid with pKa values for its three releasable protons at much higher values, and even at pH 6, much of it is not fully ionized.

One could do an alk titration with it, but in preparation for that complex experiment, one would need to first determine exactly how ionized the citric acid is at various pH values near the normal pH endpoint of an alk titration (low to mid 4’s).

 

[Randy Holmes-Farley]

The comments about muriatic and sulfuric acid seem misleading. Folks are not using highly concentrated acids for alk titrations.

0.1 N HCl and H2SO4 are not releasing to the air to any important extent. In fact,without looking carefully into it, I’m not even sure whether at very long times open to the air, 0.1 N HCl gets stronger or weaker over time. It will not penetrate plastic to any important extent.

 

[Dennis Cartier]

The comments about muriatic and sulfuric acid seem misleading. Folks are not using highly concentrated acids for alk titrations.

0.1 N HCl and H2SO4 are not releasing to the air to any important extent. In fact,without looking carefully into it, I’m not even sure whether at very long times open to the air, 0.1 N HCl gets stronger or weaker over time. It will not penetrate plastic to any important extent.

Thank you Randy.

 

[Dennis Cartier]

The comments about muriatic and sulfuric acid seem misleading. Folks are not using highly concentrated acids for alk titrations.

0.1 N HCl and H2SO4 are not releasing to the air to any important extent. In fact,without looking carefully into it, I’m not even sure whether at very long times open to the air, 0.1 N HCl gets stronger or weaker over time. It will not penetrate plastic to any important extent.

Would that apply to 10M muriatic acid as well Randy? I would be using 10M HCL (muriatic acid) to dilute down to 0.1N.

I just want to make sure that the concentrated solution, which could last me for a very, very long time, would not slowly weaken over time.

 

[Randy Holmes-Farley]

Would that apply to 10M muriatic acid as well Randy? I would be using 10M HCL (muriatic acid) to dilute down to 0.1N.

I just want to make sure that the concentrated solution, which could last me for a very, very long time, would not slowly weaken over time.

If left open, I am not certain if it gets stronger or weaker over time. The answer may depend on the humidity. If it is generally kept closed, it’s no concern.

HCl is a curious situation since both the HCl and the water can evaporate. In a mix that is 20.2% HCl, then you can boil it and even though both water and HCl are leaving, the concentration is unchanged. At lower HCl it gets more concentrated as it boils until you reach 20.2%. At room temp open to zero humidity air it will concentrate. In humid air, the effect will depend on humidity. At 100% humidity it will weaken.

Best to keep them closed when not in use. lol

 

[Dennis Cartier]

If left open, I am not certain if it gets stronger or weaker over time. The answer may depend on the humidity. If it is generally kept closed, it’s no concern.

HCl is a curious situation since both the HCl and the water can evaporate. In a mix that is 20.2% HCl, then you can boil it and even though both water and HCl are leaving, the concentration is unchanged. At lower HCl it gets more concentrated as it boils until you reach 20.2%. At room temp open to zero humidity air it will concentrate. In humid air, the effect will depend on humidity. At 100% humidity it will weaken.

Best to keep them closed when not in use. lol

Ah, OK, so no issue if tightly closed.

Thanks Randy