Monday, August 31, 2009

Why are Hospitals Cold?

This week I learned why the temperature is kept so cold in hospitals. In the mid 1800s there was a dominant idea that bad air quality caused disease. Therefore in order to treat sickness, an American physician and humanitarian, John Gorrie, built a refrigerator with the purpose of cooling air. Gorrie's refrigerator produced ice which he suspended from the ceiling in a basin.

Strange how an idea can stick with us over all these years.

While we are on the subject of ice I have recently been studying ice cubes for a project that I am working on. Specifically, I was researching the white flakes that can be found at the bottom of a glass of ice water after the ice has melted. I found that that as the ice cubes melt they precipitate white flakes, commonly known as "floaters". They are calcium carbonate, which is present in many water supplies and is completely harmless in small quantities.

Calcium carbonate is a chemical compound with the chemical formula CaCO3. It is a common substance found in rock in all parts of the world, and is the main component of shells of marine organisms, snails, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime, and is usually the principal cause of hard water. It is commonly used medicinally as a calcium supplement or as an antacid, but high consumption can be hazardous.

An interesting characteristic of commercially made ice cubes is that they are completely clear, lacking the clouding found in the center of domestically made ice cubes. As it turns out, cloudy ice cubes result when water is frozen quickly, or ice is allowed to form on the surface of the water.

When water is cooled to its freezing point, and ice starts to form, dissolved gases can no longer stay in solution and come out as microscopic bubbles. However, as ice floats in water, once there is enough ice to form a layer on the surface, the ice layer traps all bubbles within the ice cube. Ice-makers use a flowing source of water to make ice with cooling elements at the bottom, allowing the bubbles to be washed away from the top as the cube grows.

Ice Cube Trays

In the winter of 1928, Lloyd Groff Copeman was collecting sap for maple syrup on his farm. As he walked through the woods, he noticed that the ice flaked off of his rubber boots and an idea came to him. After studying this phenomenon he designed and patented different types of ice cube trays. The first was a metal tray with rubber separators, a metal tray with individual rubber cups, and even a tray made completely of rubber.

The first flexible stainless steel, all-metal ice cube tray was created by Guy L. Tinkham in 1933. The tray bent sideways to remove the ice cubes.