How do we separate the seemingly inseparable Iddo Magen
Your cell phone is mainly made
of plastics and metals.
It’s easy to appreciate
the inventive process
by which those elements are made to add up
to something so useful and entertaining.
But there’s another story
we don’t hear about as much.
How did we get our raw ingredients
in the first place
from the chaotic tangle of materials
that is nature?
The answer is a group of clever hacks
known as separation techniques.
They work by taking advantage
of the fundamental properties of things
to disentangle them from each other.
Simple separation techniques
apply to many physical scenarios,
like separating cream from milk,
extracting water from soil,
or even sifting out flecks of gold
from river sand.
But not all mixtures
are so easy to unravel.
In some of those cases,
we can exploit the differences between
physical properties within a mixture,
like particle size,
density,
or boiling point
to extract what’s required.
Take petroleum,
a mixture of different
types of hydrocarbons.
Some of these are valuable as fuels,
and others make good raw materials
for generating electric power.
To separate them, experts rely on one
important feature:
different hydrocarbons boil
at different temperatures.
During the boiling process,
each type vaporizes at a precise point,
then gets separately funneled
into a container
and collected as a liquid as it cools.
Separation techniques
also take us to the sea.
In some drought-stricken countries,
the ocean is the only
available water source.
But of course,
humans can’t drink salt water.
One way to get around this problem
is to remove salt from sea water
with reverse osmosis,
a process that separates
water’s ingredients by size.
A membrane with pores
bigger than water particles,
but smaller than salt particles,
only lets fresh water pass through,
transforming what was once undrinkable
into a life saver.
Meanwhile in the medical world,
blood tests are a vital tool
for evaluating a person’s health,
but doctors typically
can’t examine blood samples
until they’ve separated
the solid blood cells
from the liquid plasma
they’re dissolved in.
To do that, a powerful rotational force
is exerted on the test tube,
causing heavier substances
with higher density,
like blood cells,
to move away from the rotational axis.
Meanwhile, lighter substances
with lower density,
like plasma,
move to its center.
The tube’s contents divide clearly,
and the blood cells and liquid plasma
can be tested independently.
But sometimes, unlike oil,
seawater, and blood,
the parts of mixtures
that we want to separate
share the same physical properties.
In these cases, the only way to isolate
ingredients is by chemical separation,
a complex process that relies
on unique interactions
between components within a mixture
and another material.
One of these methods is chromatography,
a tool forensic scientists use
to examine crime scenes.
They dissolve gathered evidence in a gas,
and can monitor
and analyze the ingredients
as they separate
and move at varying speeds
due to their unique chemical properties.
That information then tells scientists
precisely what was present at the scene,
often helping to identify the culprit.
Separation techniques are not just about
industry,
infrastructure,
medicine,
and justice.
One of the most technically ambitious
projects in human history
is a separation technique aimed at
answering the fundamental question,
“What is the Universe made of?”
By accelerating particles
to extremely high speeds
and smashing them into each other,
we can break them into
their constituent parts ever so briefly.
And if we succeed at that, what’s next?
Is there a most elementary particle?
And if so, what’s it made of?