I was wondering if anyone could help troubleshoot an experiment I'm working on.

I'm running an experiment to measure the microbial respiration of compost samples using a $$\ce{NaOH}$$ trap. Each sample is in a jar with 20 ml of 1M $$\ce{NaOH}$$ and is placed in an incubator for 24 hrs. After 24 hrs, 20ml of .5N BaCl2 and an indicator are added to the $$\ce{NaOH}$$ and it is then titrated with $$\ce{HCl}$$. I run a few blanks each time, with an $$\ce{NaOH}$$ trap in a jar without a compost sample. This is repeated over 4 days In theory, I should need less $$\ce{HCl}$$ to neutralize the $$\ce{NaOH}$$ which has been sitting with the compost samples then the $$\ce{NaOH}$$ just by itself. Sadly, after hours and hours of work in the lab, this has not been the case!

I have 45 different samples of different types of compost. Each time I run the test, about a third of the samples require more $$\ce{HCl}$$ to neutralize than the blank.

The blanks are all consistent in the amount of $$\ce{HCl}$$ needed, I ran three last night and one the night before. The test also seems to be picking up samples which are respiring heavily- when there are moldy samples, they require only a small amount of $$\ce{HCl}$$. I can't really decipher a trend with the ones that require more $$\ce{HCl}$$ to titrate than the blank other than that it's somewhat consistent. 41% of the samples which needed more $$\ce{HCl}$$ than the blank on day 2 also needed more on day 1, and of the day 2 "error samples", 88% were from a treatment which had an "error sample" on day 1.

I thought perhaps this had to do with ammonia volatilizing from some of the samples, but this doesn't necessarily make sense with the samples which are taking more $$\ce{HCl}$$ than the blank. I also noticed that on the samples which require more $$\ce{HCl}$$ to titrate than the blank, there seems to be more precipitate (barium carbonate?) that settles out after the titration.

Do you have any idea what could be happening or what I am doing incorrectly? It's definitely a long process to do this measurement for 48 replicates over 4 days - I'm hoping the data isn't totally worthless.

Thanks

Edit: Pictures

On the left are samples which required less HCl to neutralize than the blank. (I forgot to add an extra 20ml of BaCl2 to the second from left, which I had added an additional 10 ml NaOH to, so that one is an error). In the middle is the blank and a sample which required the same amount of HCl to neutralize as the blank. Then on the right are samples which required more HCl than the blank to neutralize.

I was wondering if anyone could help troubleshoot an experiment I'm working on.

I'm running an experiment to measure the microbial respiration of compost samples using a $$\ce{NaOH}$$ trap. Each sample is in a jar with 20 ml of 1M $$\ce{NaOH}$$ and is placed in an incubator for 24 hrs. After 24 hrs, 20ml of .5N BaCl2 and an indicator are added to the $$\ce{NaOH}$$ and it is then titrated with $$\ce{HCl}$$. I run a few blanks each time, with an $$\ce{NaOH}$$ trap in a jar without a compost sample. This is repeated over 4 days In theory, I should need less $$\ce{HCl}$$ to neutralize the $$\ce{NaOH}$$ which has been sitting with the compost samples then the $$\ce{NaOH}$$ just by itself. Sadly, after hours and hours of work in the lab, this has not been the case!

I have 45 different samples of different types of compost. Each time I run the test, about a third of the samples require more $$\ce{HCl}$$ to neutralize than the blank.

The blanks are all consistent in the amount of $$\ce{HCl}$$ needed, I ran three last night and one the night before. The test also seems to be picking up samples which are respiring heavily- when there are moldy samples, they require only a small amount of $$\ce{HCl}$$. I can't really decipher a trend with the ones that require more $$\ce{HCl}$$ to titrate than the blank other than that it's somewhat consistent. 41% of the samples which needed more $$\ce{HCl}$$ than the blank on day 2 also needed more on day 1, and of the day 2 "error samples", 88% were from a treatment which had an "error sample" on day 1.

I thought perhaps this had to do with ammonia volatilizing from some of the samples, but this doesn't necessarily make sense with the samples which are taking more $$\ce{HCl}$$ than the blank. I also noticed that on the samples which require more $$\ce{HCl}$$ to titrate than the blank, there seems to be more precipitate (barium carbonate?) that settles out after the titration.

Do you have any idea what could be happening or what I am doing incorrectly? It's definitely a long process to do this measurement for 48 replicates over 4 days - I'm hoping the data isn't totally worthless.

Thanks

I was wondering if anyone could help troubleshoot an experiment I'm working on.

I'm running an experiment to measure the microbial respiration of compost samples using a $$\ce{NaOH}$$ trap. Each sample is in a jar with 20 ml of 1M $$\ce{NaOH}$$ and is placed in an incubator for 24 hrs. After 24 hrs, 20ml of .5N BaCl2 and an indicator are added to the $$\ce{NaOH}$$ and it is then titrated with $$\ce{HCl}$$. I run a few blanks each time, with an $$\ce{NaOH}$$ trap in a jar without a compost sample. This is repeated over 4 days In theory, I should need less $$\ce{HCl}$$ to neutralize the $$\ce{NaOH}$$ which has been sitting with the compost samples then the $$\ce{NaOH}$$ just by itself. Sadly, after hours and hours of work in the lab, this has not been the case!

I have 45 different samples of different types of compost. Each time I run the test, about a third of the samples require more $$\ce{HCl}$$ to neutralize than the blank.

The blanks are all consistent in the amount of $$\ce{HCl}$$ needed, I ran three last night and one the night before. The test also seems to be picking up samples which are respiring heavily- when there are moldy samples, they require only a small amount of $$\ce{HCl}$$. I can't really decipher a trend with the ones that require more $$\ce{HCl}$$ to titrate than the blank other than that it's somewhat consistent. 41% of the samples which needed more $$\ce{HCl}$$ than the blank on day 2 also needed more on day 1, and of the day 2 "error samples", 88% were from a treatment which had an "error sample" on day 1.

I thought perhaps this had to do with ammonia volatilizing from some of the samples, but this doesn't necessarily make sense with the samples which are taking more $$\ce{HCl}$$ than the blank. I also noticed that on the samples which require more $$\ce{HCl}$$ to titrate than the blank, there seems to be more precipitate (barium carbonate?) that settles out after the titration.

Do you have any idea what could be happening or what I am doing incorrectly? It's definitely a long process to do this measurement for 48 replicates over 4 days - I'm hoping the data isn't totally worthless.

Thanks

Edit: Pictures

On the left are samples which required less HCl to neutralize than the blank. (I forgot to add an extra 20ml of BaCl2 to the second from left, which I had added an additional 10 ml NaOH to, so that one is an error). In the middle is the blank and a sample which required the same amount of HCl to neutralize as the blank. Then on the right are samples which required more HCl than the blank to neutralize.

I was wondering if anyone could help troubleshoot an experiment I'm working on.

I'm running an experiment to measure the microbial respiration of compost samples using a NaOH$$\ce{NaOH}$$ trap. Each sample is in a jar with 20 ml of 1M NaOH$$\ce{NaOH}$$ and is placed in an incubator for 24 hrs. After 24 hrs, 20ml of .5N BaCl2 and an indicator are added to the NaOH$$\ce{NaOH}$$ and it is then titrated with HCl$$\ce{HCl}$$. I run a few blanks each time, with an NaOH$$\ce{NaOH}$$ trap in a jar without a compost sample. This is repeated over 4 days In theory, I should need less HCl$$\ce{HCl}$$ to neutralize the NaOH$$\ce{NaOH}$$ which has been sitting with the compost samples then the NaOH$$\ce{NaOH}$$ just by itself. Sadly, after hours and hours of work in the lab, this has not been the case!

I have 45 different samples of different types of compost. Each time I run the test, about a third of the samples require more HCl$$\ce{HCl}$$ to neutralize than the blank.

The blanks are all consistent in the amount of HCl$$\ce{HCl}$$ needed, I ran three last night and one the night before. The test also seems to be picking up samples which are respiring heavily- when there are moldy samples, they require only a small amount of HCl$$\ce{HCl}$$. I can't really decipher a trend with the ones that require more HCl$$\ce{HCl}$$ to titrate than the blank other than that it's somewhat consistent. 41% of the samples which needed more HCl$$\ce{HCl}$$ than the blank on day 2 also needed more on day 1, and of the day 2 "error samples", 88% were from a treatment which had an "error sample" on day 1.

I thought perhaps this had to do with ammonia volatilizing from some of the samples, but this doesn't necessarily make sense with the samples which are taking more HCl$$\ce{HCl}$$ than the blank. I also noticed that on the samples which require more HCl$$\ce{HCl}$$ to titrate than the blank, there seems to be more precipitate (barium carbonate?) that settles out after the titration.

Do you have any idea what could be happening or what I am doing incorrectly? It's definitely a long process to do this measurement for 48 replicates over 4 days - I'm hoping the data isn't totally worthless.

Thanks

I was wondering if anyone could help troubleshoot an experiment I'm working on.

I'm running an experiment to measure the microbial respiration of compost samples using a NaOH trap. Each sample is in a jar with 20 ml of 1M NaOH and is placed in an incubator for 24 hrs. After 24 hrs, 20ml of .5N BaCl2 and an indicator are added to the NaOH and it is then titrated with HCl. I run a few blanks each time, with an NaOH trap in a jar without a compost sample. This is repeated over 4 days In theory, I should need less HCl to neutralize the NaOH which has been sitting with the compost samples then the NaOH just by itself. Sadly, after hours and hours of work in the lab, this has not been the case!

I have 45 different samples of different types of compost. Each time I run the test, about a third of the samples require more HCl to neutralize than the blank.

The blanks are all consistent in the amount of HCl needed, I ran three last night and one the night before. The test also seems to be picking up samples which are respiring heavily- when there are moldy samples, they require only a small amount of HCl. I can't really decipher a trend with the ones that require more HCl to titrate than the blank other than that it's somewhat consistent. 41% of the samples which needed more HCl than the blank on day 2 also needed more on day 1, and of the day 2 "error samples", 88% were from a treatment which had an "error sample" on day 1.

I thought perhaps this had to do with ammonia volatilizing from some of the samples, but this doesn't necessarily make sense with the samples which are taking more HCl than the blank. I also noticed that on the samples which require more HCl to titrate than the blank, there seems to be more precipitate (barium carbonate?) that settles out after the titration.

Do you have any idea what could be happening or what I am doing incorrectly? It's definitely a long process to do this measurement for 48 replicates over 4 days - I'm hoping the data isn't totally worthless.

Thanks

I was wondering if anyone could help troubleshoot an experiment I'm working on.

I'm running an experiment to measure the microbial respiration of compost samples using a $$\ce{NaOH}$$ trap. Each sample is in a jar with 20 ml of 1M $$\ce{NaOH}$$ and is placed in an incubator for 24 hrs. After 24 hrs, 20ml of .5N BaCl2 and an indicator are added to the $$\ce{NaOH}$$ and it is then titrated with $$\ce{HCl}$$. I run a few blanks each time, with an $$\ce{NaOH}$$ trap in a jar without a compost sample. This is repeated over 4 days In theory, I should need less $$\ce{HCl}$$ to neutralize the $$\ce{NaOH}$$ which has been sitting with the compost samples then the $$\ce{NaOH}$$ just by itself. Sadly, after hours and hours of work in the lab, this has not been the case!

I have 45 different samples of different types of compost. Each time I run the test, about a third of the samples require more $$\ce{HCl}$$ to neutralize than the blank.

The blanks are all consistent in the amount of $$\ce{HCl}$$ needed, I ran three last night and one the night before. The test also seems to be picking up samples which are respiring heavily- when there are moldy samples, they require only a small amount of $$\ce{HCl}$$. I can't really decipher a trend with the ones that require more $$\ce{HCl}$$ to titrate than the blank other than that it's somewhat consistent. 41% of the samples which needed more $$\ce{HCl}$$ than the blank on day 2 also needed more on day 1, and of the day 2 "error samples", 88% were from a treatment which had an "error sample" on day 1.

I thought perhaps this had to do with ammonia volatilizing from some of the samples, but this doesn't necessarily make sense with the samples which are taking more $$\ce{HCl}$$ than the blank. I also noticed that on the samples which require more $$\ce{HCl}$$ to titrate than the blank, there seems to be more precipitate (barium carbonate?) that settles out after the titration.

Do you have any idea what could be happening or what I am doing incorrectly? It's definitely a long process to do this measurement for 48 replicates over 4 days - I'm hoping the data isn't totally worthless.

Thanks

1

# NaOH CO2 trap troubleshooting

I was wondering if anyone could help troubleshoot an experiment I'm working on.

I'm running an experiment to measure the microbial respiration of compost samples using a NaOH trap. Each sample is in a jar with 20 ml of 1M NaOH and is placed in an incubator for 24 hrs. After 24 hrs, 20ml of .5N BaCl2 and an indicator are added to the NaOH and it is then titrated with HCl. I run a few blanks each time, with an NaOH trap in a jar without a compost sample. This is repeated over 4 days In theory, I should need less HCl to neutralize the NaOH which has been sitting with the compost samples then the NaOH just by itself. Sadly, after hours and hours of work in the lab, this has not been the case!

I have 45 different samples of different types of compost. Each time I run the test, about a third of the samples require more HCl to neutralize than the blank.

The blanks are all consistent in the amount of HCl needed, I ran three last night and one the night before. The test also seems to be picking up samples which are respiring heavily- when there are moldy samples, they require only a small amount of HCl. I can't really decipher a trend with the ones that require more HCl to titrate than the blank other than that it's somewhat consistent. 41% of the samples which needed more HCl than the blank on day 2 also needed more on day 1, and of the day 2 "error samples", 88% were from a treatment which had an "error sample" on day 1.

I thought perhaps this had to do with ammonia volatilizing from some of the samples, but this doesn't necessarily make sense with the samples which are taking more HCl than the blank. I also noticed that on the samples which require more HCl to titrate than the blank, there seems to be more precipitate (barium carbonate?) that settles out after the titration.

Do you have any idea what could be happening or what I am doing incorrectly? It's definitely a long process to do this measurement for 48 replicates over 4 days - I'm hoping the data isn't totally worthless.

Thanks