Determine atomic mass of isotopes with chemistry.

[avicenna]

I know we can get the relative atomic mass of any two nuclides by just looking up the CODATA.
But I'll like to know if anyone has measured atomic mass with a chemical process.

Say we analyze the weight composition of ¹H₂¹⁶O to get the relative mass of ¹⁶O/¹H. Or of any other two elements through any chemical process.  

 

[studiot]

2 hours ago, avicenna said:

I know we can get the relative atomic mass of any two nuclides by just looking up the CODATA.
But I'll like to know if anyone has measured atomic mass with a chemical process.

Say we analyze the weight composition of ¹H₂¹⁶O to get the relative mass of ¹⁶O/¹H. Or of any other two elements through any chemical process.  

 

Well I'm not sure exactly what information you are seeking here, but the story of how it was all worked out is fascinating.

The process took almost 200 years from about 1660 to the Cannizzaro paper of 1858, via the hypothesis of Avogadro in 1811.

There were many blind alleys and false trails along the way, and many famous names contributed sometimes adding correct insights, sometimes getting it hopelessly wrong.

The story is too much to put into a forum post, and is in fact the subject of a book in its own right.

 

Chasing the Molecule

by

John Buckingham.

 

 

Edited June 23, 2018 by studiot

[John Cuthber]

Or with a questionable definition of "chemistry"...

https://en.wikipedia.org/wiki/Mass_spectrometry

 

It is possible to observe isotope mass effects with chemistry.

According to this data
https://en.wikipedia.org/wiki/Isotopes_of_lead

you can get samples of lead that have between 51 and 56 % 208Pb

That would be a big enough range to detect if you measured the molar mass by classical wet chemistry.

Edited June 23, 2018 by John Cuthber

[avicenna]

36 minutes ago, John Cuthber said:

Or with a questionable definition of "chemistry"...

https://en.wikipedia.org/wiki/Mass_spectrometry

 

It is possible to observe isotope mass effects with chemistry.

According to this data
https://en.wikipedia.org/wiki/Isotopes_of_lead

you can get samples of lead that have between 51 and 56 % 208Pb

That would be a big enough range to detect if you measured the molar mass by classical wet chemistry.

I know isotopes exists. What I am really interested is getting the actual relative atomic mass using our chemical balances and not through mass spectrometry. Then compare it with the CODATA.

Has anyone ever checked if their scales don't give short weights and measures! Even in ancient times, officials would come to check the scales you use to measure grains. What if mass spectrometry is off! Avicenna would even ask if God exists.

 

[John Cuthber]

The atomic masses were determined (often to quite high accuracy) well before there were any mass spectrometers.

For example, you can take a gram of hydrogen(mixed with nitrogen r something else that won't react), and pass it over hot copper oxide.

The hydrogen will be oxidised to water.
You can trap that water by passing the gas over phosphorus pentoxide.

And you can weigh the water.

You will get 9 grams of water and so you know that the mass of oxygen that combines with 1 gram of hydrogen is 8 grams .

It gets a bit more complicated when you try to decide if water is HO H₂O HO₂ or what, but it was pretty much all worked out by classical chemistry.

 

[avicenna]

14 minutes ago, John Cuthber said:

The atomic masses were determined (often to quite high accuracy) well before there were any mass spectrometers.

For example, you can take a gram of hydrogen(mixed with nitrogen r something else that won't react), and pass it over hot copper oxide.

The hydrogen will be oxidised to water.
You can trap that water by passing the gas over phosphorus pentoxide.

And you can weigh the water.

You will get 9 grams of water and so you know that the mass of oxygen that combines with 1 gram of hydrogen is 8 grams .

It gets a bit more complicated when you try to decide if water is HO H₂O HO₂ or what, but it was pretty much all worked out by classical chemistry.

 

What you get is only the classical atomic weights. In nature H has 0.02% deuterium. O has O16, O17 and O18 in various %. So the old atomic weights is a mixture of isotopes. We need H₂O that is made from pure isotope ¹H and pure isotope ¹⁶O. Only then can we get real relative atomic mass to compare with the CODATA obtained from mass spectrometry..

 

[John Cuthber]

That's why a chose lead as an example.
You can get nearly pure 208Pb by isolating lead from thorium minerals.

You can compare it to lead from other sources and show that there are differences.
Getting other pure isotopes is tricky.
You can get monoisotopic mercury by neutron irradiation of (naturally single isotope) gold.

[studiot]

55 minutes ago, avicenna said:

Avicenna would even ask if God exists.

 

But appears convinced that studiot does not exist.

[StringJunky]

1 hour ago, studiot said:

 

But appears convinced that studiot does not exist.

Have a rep for trying.  

[studiot]

Well thank you kind sir.

 

[Sensei]

On 23.06.2018 at 9:37 PM, studiot said:

But appears convinced that studiot does not exist.

What if studiot is just AI/AGI on my "hard disk".. ? How would you define "existence".. ?

ps. Imagine temptation of shutting/not shutting down D.T. or V.P....

 

Edited June 27, 2018 by Sensei