DIY Alkatronic reagent

[BrianReefer]

I could only get a 250ml bottle of 1.0M (2.0N) solution of Sulfuric Acid. I see some posts mentioning diluting the 1.0M solution at a 1:9 ratio to get a .1N concentration. However, isn't 1.0M actually 2.0N and therefore needs to be diluted to 1:18?
For example,
50ml of 1.0M (2.0N) Sulfuric Acid diluted with 950ml water makes .1N solution.

Is this correct?

How did this mix work out for you? amazon no longer carries the .1N so I may also have to buy the 1.0M (2N) Sulfuric Acid bottle. Any issues by mixing with 950ml RODI? I assume others have the same issue...you can find the .1N elsewhere but it's $70 vs the $45 it used to be on amazon, so this 1 Liter bottle of 1.0M for $22 seems like a better buy, if it works

 

[ReeferBud]

How did this mix work out for you? amazon no longer carries the .1N so I may also have to buy the 1.0M (2N) Sulfuric Acid bottle. Any issues by mixing with 950ml RODI? I assume others have the same issue...you can find the .1N elsewhere but it's $70 vs the $45 it used to be on amazon, so this 1 Liter bottle of 1.0M for $22 seems like a better buy, if it works

That’s exactly what I’m doing. Chemistry works.

 

[thatmanMIKEson]

How did this mix work out for you? amazon no longer carries the .1N so I may also have to buy the 1.0M (2N) Sulfuric Acid bottle. Any issues by mixing with 950ml RODI? I assume others have the same issue...you can find the .1N elsewhere but it's $70 vs the $45 it used to be on amazon, so this 1 Liter bottle of 1.0M for $22 seems like a better buy, if it works

Do you have a link for this?

Is it not 1 liter to 4 liters of rodi?

 

[thatmanMIKEson]

That’s exactly what I’m doing. Chemistry works.

For chemists.... I still can't count with out my fingers

 

[Randy Holmes-Farley Verified Community Expert]

Do you have a link for this?

Is it not 1 liter to 4 liters of rodi?

Dilution works like this:

Cf = final concentration
Ci = initial concentration
Vi = initial volume of solution with chemical
Vf = final volume of combined fluids

Cf = Ci x (Vi/Vf)

FWIW, 1 M sulfuric acid is 2 N sulfuric acid.

The statement was:

"50ml of 1.0M (2.0N) Sulfuric Acid diluted with 950ml water makes .1N solution."

Using our equation:

Cf = 2 N x (50/(50+950)) = 2N x 0.05 = 0.1 N

 

[Dennis Cartier]

Hmm, this is not good news. That was one of the few standards that I could import into Canada.

Randy, would 75% Food Grade Vinegar be able to be substituted (with appropriate dilution)? Any issues with stability or bacterial growth at low concentration?

 

[Randy Holmes-Farley Verified Community Expert]

Hmm, this is not good news. That was one of the few standards that I could import into Canada.

Randy, would 75% Food Grade Vinegar be able to be substituted (with appropriate dilution)? Any issues with stability or bacterial growth at low concentration?

For an alkalinity titration that uses the normal pH endpoint? No. It is not a strong enough acid. At the pH endpoint in the low 4's, there is a fair amount of acetic acid left unionized.

If one wanted to come up with some sort of correction factor, it might be possible. Something like 0.13 M acetic acid is equivalent to 0.1 M hydrochloric acid in a seawater pH titration, but one would need to develop that experimentally.

I discuss how acetate/acetic acid in partly ionized at the alkalinity endpoint here:

Chemistry and the Aquarium: What is Alkalinity?

Randy provides an overview of alkalinity as to why it's important, how it's measured, and how can it be tested.

reefs.com

 

[Dennis Cartier]

In that case, I have made an account with a Laboratory Supply company. Fingers crossed they will sell to the public. 4L of 0.1N from them costs about double what Amazon charged, but they sell 1N for the same amount. So diluting it myself will be the plan.

 

[BrianReefer]

In that case, I have made an account with a Laboratory Supply company. Fingers crossed they will sell to the public. 4L of 0.1N from them costs about double what Amazon charged, but they sell 1N for the same amount. So diluting it myself will be the plan.

Dennis, Amazon in US still has the more concentrated 2N solution for way less $, if they don’t have that in Canada I can get it and send it up your way!

 

[JeffB418]

Coralvue sells the same stuff amazon had for $54/4L (0.1N)

Alkalinity Testing Machine Concentrated Reagent

A concentrated reagent for the Alkatronic Alkalinity Controller. For every 1 part reagent, mix 4 parts RO/DI water. Every 1000mL of concentrate will produce 50000mL of solution.

www.coralvue.com

 

[BrianReefer]

Coralvue sells the same stuff amazon had for $54/4L (0.1N)

Alkalinity Testing Machine Concentrated Reagent

A concentrated reagent for the Alkatronic Alkalinity Controller. For every 1 part reagent, mix 4 parts RO/DI water. Every 1000mL of concentrate will produce 50000mL of solution.

www.coralvue.com

Good catch!

 

[JeffB418]

Good catch!

Free shipping too!

 

[JeffB418]

Coralvue sells the same stuff amazon had for $54/4L (0.1N)

Alkalinity Testing Machine Concentrated Reagent

A concentrated reagent for the Alkatronic Alkalinity Controller. For every 1 part reagent, mix 4 parts RO/DI water. Every 1000mL of concentrate will produce 50000mL of solution.

www.coralvue.com

wayyyyyyyy better price than BRS is charging... https://www.bulkreefsupply.com/alka...=15252&indexName=brs_prod_m2_default_products

 

[Randy Holmes-Farley Verified Community Expert]

I still find it shockingly expensive since the actual materials cost is very low. Of the $54 mentioned above, not more than a few percent can be for the actual acid.

$10 for a gallon of muriatic acid can make 100 gallons of 0.1 N HCl. Yes, there is time and effort to dilute and standardize it.

 

[Dennis Cartier]

I still find it shockingly expensive since the actual materials cost is very low. Of the $54 mentioned above, not more than a few percent can be for the actual acid.

$10 for a gallon of muriatic acid can make 100 gallons of 0.1 N HCl. Yes, there is time and effort to dilute and standardize it.

I can get 20 baume muriatic acid locally. I am just uncertain of the dilution factor and if the strength is uniform, bottle to bottle.

 

[Randy Holmes-Farley Verified Community Expert]

I can get 20 baume muriatic acid locally. I am just uncertain of the dilution factor and if the strength is uniform, bottle to bottle.

That is the concern. The time and effort to determine the exact concentration by pH titration with a standard base is not worth it for most folks.

 

[jtichenor]

For an easy formula for using 2.0N Sulfuric acid..

• 25ml (2N) acid mixed with 2475ml RO water makes 2.5L reagent
• 50ml (2N) acid mixed with 4950ml RO water makes 5L reagent

As of this post, 500ml of 2.0N Sulfuric acid is $22 on Amazon. So it costs $2.20 to make 5L of reagent

 

[Dennis Cartier]

I still find it shockingly expensive since the actual materials cost is very low. Of the $54 mentioned above, not more than a few percent can be for the actual acid.

$10 for a gallon of muriatic acid can make 100 gallons of 0.1 N HCl. Yes, there is time and effort to dilute and standardize it.

That is the concern. The time and effort to determine the exact concentration by pH titration with a standard base is not worth it for most folks.

I thought about this some more. I think that, at least in my case, it's probably worth it to go through the effort of determining the exact concentration of a muriatic acid sample. I use about 1L of reagent a month. At the expected strength of around 10M, for a 20 baume HCL sample, a 4L bottle would last me 133 years when diluted down to 0.02N of reagent.

It gives me a reason to buy a variable volume pipette, which I will need anyway for an experiment I am running in the research forum.

 

[Randy Holmes-Farley Verified Community Expert]

I thought about this some more. I think that, at least in my case, it's probably worth it to go through the effort of determining the exact concentration of a muriatic acid sample. I use about 1L of reagent a month. At the expected strength of around 10M, for a 20 baume HCL sample, a 4L bottle would last me 133 years when diluted down to 0.02N of reagent.

It gives me a reason to buy a variable volume pipette, which I will need anyway for an experiment I am running in the research forum.

Let us know how it works out!

 

[Dennis Cartier]

Randy shield your eyes to my unorthodox methods ...

I worked a bit on trying to determine how strong the 20 baume HCL acid I have is. For a start I wanted to test a method of comparing the strength of known and unknown solutions. I had on the shelf what was supposed to be a 7 dKH standard (that I made awhile ago). I tested it with my Hanna, and it tested at 113 ppm, 6.32 dKH. I don't recall if it really was a 7 dKH solution, but do remember being a bit disappointed, so the Hanna is probably correct in this case.

Based on the Hanna reading, I calculated that 225 uL of the 0.1N sulpheric standard that I use for the Alkatronic reagent should drop the alk reading by 50%. I performed the dilution and tested with the Hanna and got 57 ppm, 3.19 dKH. I was pretty satisfied with the result and confirmation of my calculations.

The next step is to attempt to find what dilution of the HCL will provide the same result.

I did take a stab at a dilution of the HCL assuming it was 10N, but flubbed the dilution and accidentally used 100 uL instead of 1000 uL, and got 111 ppm, 6.21 dKH. When I noticed my mistake I added 900 uL (of the HCL) to the volume, and got 66 ppm, 3.69 dKH. My gut says that the HCL is probably just under 10N, as the extra 900 uL added to the 100 ml can't account for the difference. The fact I was using a beaker and not a volumetric flask for the dillution probably had a bigger effect, than the extra volume. So not too close, but headed in the right direction.

These were all based on very small volumes, so small errors would be amplified substantially. I plan to use much larger volumes in the next attempts to help alleviate the error amplification. I have less than 500 ml of the dKH standard, so I will switch to using tank water as I have lots of that!