What is dialysis?

It's a process that happens quite naturally in our kidneys. Blood is a complex liquid, containing cells as well as salts, proteins and water. When it passes through the kidneys, the water passes into the urinary system, while some of the salts and proteins stay back in the blood. This is because the kidney is 'semi-permeable'. That is, only tiny molecules like water can pass through, while large atoms like proteins cannot.

Dialysis is a way of doing the same thing in the hospital.

And that is where Thomas Graham comes in. He was the first one to observe and explain the process.

Colloids

Colloids are very, very tiny particles that are made up of just a few hundred atoms. A common colloid we all know and enjoy is beaten curd, or lassi. Another is lemonade. Blood (without the cells) is also a good colloid. They have many properties not shown by solutions of liquids like salt water.

Graham was the first chemist to study them. But he needed a pure colloid, in which there was nothing dissolved. After trying many methods, he found that a semi-permeable membrane worked best. On one side you put the impure colloid, and on the other side you have pure water. The salt molecules cross the membrane into the pure water, but the colloid particles cannot.

For a long time, dialysis was useful only in chemistry labs. It was only in 1944, that Dutch doctor Willem Kolff managed to build the first practical dialysis machine for patients of kidney failure.

Have you seen (on TV) firemen rushing into a burning building with gas masks on? The masks contain charcoal, which can absorb all manner of poisonous gases. This discovery too was made by Thomas Graham.

Graham's Law

Thomas Graham is also known for his study of the diffusion of gases. What it says is that a gas will diffuse slowly if it is heavier than air and faster if it is lighter. It's very important for making perfumes. Essential oils which are lighter than air (when they evaporate) make up the top notes, while those that are heavier make the base notes. The correct mix to be made is calculated using Graham's Law.

Life

Graham was born on December 21st, 1805 in Glasgow, Scotland. Though his father wanted him to be a priest, he chose to study chemistry instead. He got his M.A. in Chemistry in 1826. In 1837, he moved to University College London as Professor of Chemistry.

In 1841, along with John Dalton, he founded the Chemical Society, the world's first association of chemists. Apart from the chemistry of gases and colloids, he also made discoveries about phosphorus, palladium, charcoal, coffee and alcohol. After a long career, he died in 1869.