Metanil yellow in tumeric

[adrian2022]

Hi, Sorry if my english is bad, I read that tumeric can be tested for Metanil yellow with hydrocloric acid, I used 30% hcl and added some tumeric and it turned pink, Added some more and it tured red :/ does my tumeric contain Metanil yellow?

[studiot]

12 minutes ago, adrian2022 said:

Hi, Sorry if my english is bad, I read that tumeric can be tested for Metanil yellow with hydrocloric acid, I used 30% hcl and added some tumeric and it turned pink, Added some more and it tured red 😕 does my tumeric contain Metanil yellow?

Well the pH of 30% HCl is less than 1 and MY turn from yellow at pH 2 to red at pH 1 so it could be present, depending upon how much  HCl you added.

 

Do you know the source of your turmeric or its physical form ?

The yellow colour in turmeric is due to curcumin, which is normally neutral to alkaline pH   (greater than 7).

Here are some pictures of pH variation from 2 to 13

The curcumin color changes from pH 2-13 (a), and the curcumin UV-VIS... | Download Scientific Diagram (researchgate.net)

[adrian2022]

2 minutes ago, studiot said:

Well the pH of 30% HCl is less than 1 and MY turn from yellow at pH 2 to red at pH 1 so it could be present, depending upon how much  HCl you added.

 

Do you know the source of your turmeric or its physical form ?

Its from my grocery store, I added tumeric to a container of hci not hci to tumeric if that matters, i took 2 picutures, second picture is with more tumeric added

[studiot]

I don't have colours below pH 2, but will try the experiment.

The above is from my link

Have you tried this with turmeric from any other source ?

[adrian2022]

15 minutes ago, studiot said:

I don't have colours below pH 2, but will try the experiment.

The above is from my link

Have you tried this with turmeric from any other source ?

Yes i tried my curcumin extract supplement and got the same result

[studiot]

I tried some old turmeric from my spice drawer in some Tesco limescale remover.

Unfortunately this limescale remover has a bright blue dye so the result was a bright green solution, with no hint of red.

 

The concentration of HCl is stated as 6.75g per 100g so appears a bit weaker than yours. I will have to calculate it's pH.

 

That is the best I can do on a Sunday evening.

[adrian2022]

1 minute ago, studiot said:

I tried some old turmeric from my spice drawer in some Tesco limescale remover.

Unfortunately this limescale remover has a bright blue dye so the result was a bright green solution, with no hint of red.

 

The concentration of HCl is stated as 6.75g per 100g so appears a bit weaker than yours. I will have to calculate it's pH.

 

That is the best I can do on a Sunday evening.

Ok thank you for your help and time, I will go and buy another brand of tumeric  and test it, I forgot to mention that if i add water to the solution it goes back to light yellow

 

[studiot]

Here is a ph calculator for  HCl solutions

https://www.oxy.com/globalassets/documents/chemicals/products/chlor-alkali/tech-calculated_ph_values_hcl.pdf

[adrian2022]

11 hours ago, studiot said:

Here is a ph calculator for  HCl solutions

https://www.oxy.com/globalassets/documents/chemicals/products/chlor-alkali/tech-calculated_ph_values_hcl.pdf

I dont know how to calculate my ph, But i did another test on a pice of tumeric root and it turned pink also, Must be some contaminants in my hci or something else,

Found another test for metanil yellow but in pigeon peas https://www.studyrankers.com/2016/06/test-the-presence-of-starch-and-metanil-yellow.html

 

[studiot]

1 hour ago, adrian2022 said:

I dont know how to calculate my ph, But i did another test on a pice of tumeric root and it turned pink also, Must be some contaminants in my hci or something else,

Found another test for metanil yellow but in pigeon peas https://www.studyrankers.com/2016/06/test-the-presence-of-starch-and-metanil-yellow.html

 

I don't know what was in the other 70% of your hydrochloric acid.

What colour is it to start with?

As a matter of interest I opened one of my turmeric extract capsules (from Hey products in London).
Inside I found a yellow powder very similar in colour to the turmeric in my spice jar.
Upon testing it turned my limescale acid from bright blue to bright green, just as the spice turmeric did.
Again there was no hint of red.

Adding water just thinned the green down.

 

This is interesting.

Where did your turmeric extract capsules come from and have you found them of any value ?

I have just started trying them for my arthritis after a very strong recommendation from a friend.