Epistemic Spot Check: The Alchemy of Air (Thomas Hager)

[content warning: war, the Holocaust]


Fixed nitrogen is a startlingly important molecule, essential in both explosives and farming. Until the 1900s, turning atmospheric nitrogen (which is abundant) into fixed nitrogen was the purview of a handful of bacteria, and countries went to great length to get more.  Several wars were fought and decided over/by who had better access to nitrogen stores.

In the early 1900s, German scientist Fritz Haber invented (and engineer Carl Bosch industrialized) a process for producing fixed nitrogen.  This changed the world on a number of levels:

  • Removed the nitrogen-induced cap on the human population, which was ~4 billion people.  You know how people say it’s impossible for everyone to eat organic?  This is why.  There is not nearly enough natural fixed nitrogen to feed everyone.
  • Prolonged Germany’s involvement in World War 1 by one to two years, by both increasing the volume of explosives they had access to and by making it possible to feed people from relatively poor farmland.
  • Was part of a larger shift in Germany becoming an economic and scientific power.

The Alchemy of Air starts with a longer description of why fixed nitrogen is so important.  The meat of the book  is the invention of the Haber-Bosch process and the life stories of the two men responsible for it.  It touches on the chemistry of nitrogen, how a proof of concept becomes and industrial process at the age when those were beginning to separate.  At the end, it offers a glimpse into the rise of Hitler and the Nazi party as viewed by the scientific community.

Fact Checking

Claims: “Nitrogen is the most important element… for humans”, “more interesting than other elements.”  “Nitrogen is a/the rate limiting factor in life on Earth.  If you put more fixed nitrogen in a field, you can grow more.” (Prologue).

True-ish. I don’t know how to fact check which element is more interesting.  I went through 7 semesters of college chemistry without picking a favorite element.  But the more factual claim that nitrogen is a major limitation of growth on life on Earth checks out.  The other major elements we need- carbon, oxygen, and hydrogen- are relatively cheap to create from molecules found in the air (although oxygen is the limiting factor in certain aquatic ecosystems- and as you learn at the end of the book, fixed nitrogen abundance makes this worse).    Atmospheric nitrogen makes up 80% of the air, but it is incredibly energetically expensive to convert that into nitrogen useful to plants and animals (known as fixed nitrogen)

Claim: “N2 is [harder to break down because it is] held together with a triple bond, the strongest bond in nature.” (prologue)

True but incomplete. Nitrogen does use a triple bond.  On average, triple bonds will be more expensive to break or form than double or single bonds.  But carbon can form four bonds.  You can’t actually have a stable quadruple bonds because of complicated shape things, but they can triple bond with each other and each have a side chain.  It’s possible HCCH is just as expensive to break apart, but there’s enough carbon in easily accessible forms that it doesn’t matter.

Also, the fact that N2 (the kind of nitrogen found in the atmosphere) is expensive to break doesn’t explain why fixed nitrogen makes such an excellent explosive.  The fact that it is implies that fixed nitrogen is also energetically expensive to make.  The internet is rather lacking on this topic, but the fact that fixation is net negative on ATP (the energy currency of living things) suggests that I’m right.  “This bond stores a lot of energy” is not actually a good argument for why no one breaks it.

Claim: “Using [their complicated farming system involving three different animals and five different types of plants], the Chinese could feed as many as ten people per acre of farmland, a yield of food five to ten times greater than the European average of the 1800s” (p5)

True but misleading. Verifying this is surprisingly hard, but I do know that Chinese agriculture was incredibly labor intensive, much more so than European farming.  That’s why 1800s China has a bunch of proverbs about working hard and Europe had a bunch of proverbs about hoping it rained (source, although I’d like to do a fact check on this one).

Claim: Haber-Bosch uses 1% of the Earth’s energy (p271)

True, although this refers only to generated energy and not natural sources like the sun or underwater vents.

Claim: “Half the nitrogen in your blood, your skin and hair, your proteins and DNA, is synthetic” (p272)

False.  The atom was nitrogen when you found it and it’s nitrogen now.  The molecule that delivered it to the plant was synthetically produced, but the nitrogen has always been itself.  At a minimum, synthetic should mean you found different atoms and combined them into something new, but chemistry has an even stricter definition: elements that do not exist naturally and must be created in a lab.

Claim: “Nitrogen pollution in the water has been to linked to health problems like methemoglobinemia, or “blue baby syndrome”” (p274)

True.  The EPA supports this, although it appears there’s still some scientific controversy over exactly how large a role nitrogen plays.

Claim: Nitrogen run off causes algal blooms that devastate aquatic ecosystems (p274)


Claim: A long history of saltpeter I’m not going to transcribe fact-by-fact (chapter 1)

True.  I didn’t run down every fact but everything I could find checked out, and his conclusions (saltpeter was incredibly valuable) are supported by other information he didn’t mention.

Claim: Darwin was hired onto the Beagle as someone of suitable social stature for the captain to talk to so he didn’t go mad.


Claim: After saltpeter, bird shit became the coveted resource (chapter 3)

True. Again, I didn’t run down every single thing, but guano was the immediate catalyst for the South American colonies to revolt against the Spanish, the USA still has a law on the books allowing any citizen to claim guano rich islands for the country.

Other thoughts

Alchemy of Air is a weirdly uneven book.  I don’t think this is writing style, I think it’s just covering a lot of different material and what people find interesting varies a lot.  For example, I loved the sections on the history and economics of nitrogen, and how the Haber-Bosch industrial process for producing fixed nitrogen from the air affected World War 1.  The fourty three chapters on Bosch taking Haber’s proof of concept to a scalable industrial process?  Do not care.  Almost quit book until I remembered I could just skip them.

The parts on the personal lives of Bosch and Haber were very mixed bag.  Mostly boring, but intricately involved with the extremely interesting things that were happening at the time (~1900 to the rise of the Nazis).  Fritz Haber was a German Jew who merged love of science with love of country in his mind, and converted to Christianity in part so he could be viewed as more fully German.  The Haber-Bosch process probably bought Germany another year in World War 1, probably two.  He played a major role in inventing chemical warfare (Alchemy would have you believe he invented it, but is prone to exaggeration).  You can guess how this ends.  In 1934 he flees the country, made more difficult by the fact that the rest of the world still considers him a German war criminal.  The chemical he invented for use on Allied soldiers in WW1 is adapted for use in the concentration gas chambers in WW2.

Bosch’s life is also complicated.  Between the wars he dedicated everything he had and then some to inventing a way to synthesize gasoline.  This included collaborating with the early Nazi party for funding.  They were happy to do so because they, correctly, anticipated that an internal source of gas would be necessary in the upcoming war.  At some point Bosch realized what he’d done, made a bunch of symbolic gestures against the Nazis, and died in disgrace.  It’s weird because those symbolic gestures probably cost him a lot and accomplished nothing, whereas there’s some chance he could have prevented WW2 and the entire Holocaust by not working quite so hard to create synthetic gasoline.  By the time the Nazis were in power it might have bankrupted his company to stop, but it was still doable.  Maybe someone else would have invented synthetic gas… but Bosch’s company was uniquely well positioned to do so, and he basically willed it into existence by convincing an increasingly large collection of people to toss money at the process.  He didn’t even have to give up, he just had to try less hard on fundraising.

And of course both men have saved/enabled billions of lives by creating the process that feeds them.

I don’t know what to do with this information.  The world is complicated and I want the right thing to be obvious.


Generally reliable, moderately stylized.  I trust the author for broad strokes but not to give me non-nitrogen related nuance.

This post supported by Patreon.

4 thoughts on “Epistemic Spot Check: The Alchemy of Air (Thomas Hager)”

  1. I think it would be good to begin with a very short description of the book (I had not heard of this one). Something like “The Alchemy of Air is about the development of the Haber-Bosch process, which is used in the production of fertilizer and explosives.”

  2. > Claim: “Half the nitrogen in your blood, your skin and hair, your proteins and DNA, is synthetic” (p272)

    I suspect they meant to say “was fixed by industrial processes” here, and I think it’d be charitable to read it as such for evaluating truth of claim.

    1. I agree with you that that’s what the author meant but disagree that charity should be a guiding principle in this case. Obviously stylistic claims like “most interesting element” should be interpreted as reflections of the author’s state, not factual claims. But in the context of science education, using scientific terms absolutely correctly is important. From a scientific perspective the difference between manufacturing a molecule and manufacturing an atom is extremely important, and I’ve seen people trip over it.

      I wasn’t thrilled with the author’s tendency to say “nitrogen” when he meant fixed or bioavailable nitrogen, but did let that slide for stylistic reasons.

Comments are closed.

%d bloggers like this: