Colorless.

Can be straw yellow depending on the concentration of the dye.

Methyl red? Do you mean methyl orange? That is the indicator that is used for TKN titrations.

Dear Sir,

its methyl red according to the protocol i am following for TKN. 

 Dear sir,

Do you have an idea about how much excess alkali we need to add in the digested sample. Does it have any dilution factor or such?

Debasree,

We used 2 drops of Methyl Red but for a Kjeldahl Nitrogen determination of a solid sample (10% protein).  1.0 g sample, 10 mL of concentrated Sulfuric Acid, and 25 mL of 10 N Sodium Hydroxide.

Follow Total Kjeldahl Nitrogen for protein procedure in AOAC (Association of Official Analytical Chemists).  10 N = 50% Sodium Hydroxide Solution in Water.

i am using 4% boric acid and tit ration against 0.1 n HCL 

indicator -methyl red and bromocresol 0.1% in acetone 

Yes, follow AOAC

Dear Periyasamy sir,

What sort of instrument you are using for digestion and distillation part? Is it a automated one?

Thank you all of you for your very productive responses. 

my name karthikeyan ,then we are using digestion part automatic but distillation part manual one 

digestion time 45 min with min brown color to green color change the digestion materials 

Karhikeyan,

Then you are using a Copper Sulfate catalyst to aid the digestion.  Be sure you are using 2 Selenium granules to aid this digestion.  The Sulfuric Acid must be boiling.

You are destroying the cellular structure of the sample and then converting the Nitrogen found in proteins to Ammonium Sulfate.  This compound is converted to Ammonia gas when alkali is added in excess and then distilled over into your erlenmeyer solution.  This is the solution that is titrated.

yes but in catalyst part we are using copper sulphate and potassium sulphate-7;8 ratio

please see the ppt

OK.

Dear Periyasamy sir,

Very Very thanks for such an helpful and informative ppt. Our research group has decided to follow this methodology and do a trail. The Kjeldahl instrument we are using has been supplied by BORG and it looks pretty similar to Kemin's one. Thanks for your times and patience. 

Regards,

Debasree.

thanks and all the best

The endpoint will be colorless in this case.

The Total Kjeldahl Nitrogen (TKN) method is a widely used analytical procedure for determining the total nitrogen content in various types of samples, particularly in environmental samples like water and wastewater. The TKN method measures the sum of organic nitrogen, ammonia, ammonium ions, and other nitrogen-containing compounds in a sample, except for nitrate and nitrite.

When performing the TKN method, an indicator is used in the final step of the process, which involves titration. The most commonly used indicator for the TKN method is a mixed indicator, typically consisting of:

• Tashiro's Indicator: This is a popular choice for TKN analysis. Tashiro's indicator is a mixture of methyl red and methylene blue. During the titration process, the color changes from green to blue at the endpoint.

The titration step in the TKN method is crucial as it helps in quantifying the amount of acid required to neutralize the ammonia (which is a product of the digestion of organic nitrogen compounds in the sample). The indicator's color change signifies the endpoint of the titration, allowing for the calculation of the total nitrogen content.

To perform the TKN method accurately, it is essential to follow the standard protocols and use the appropriate reagents and indicators. The method involves several steps, including digestion, distillation, and titration, each requiring careful attention to detail for accurate results.

l Check out this protocol list; it might provide additional insights for resolving the issue.