Refrigerant gas

The invention: A safe refrigerant gas for domestic refrigerators,

dichlorodifluoromethane helped promote a rapid growth in the

acceptance of electrical refrigerators in homes.

The people behind the invention:

Thomas Midgley, Jr. (1889-1944), an American engineer and

chemist

Charles F. Kettering (1876-1958), an American engineer and

inventor who was the head of research for General Motors

Albert Henne (1901-1967), an American chemist who was

Midgley’s chief assistant

Frédéric Swarts (1866-1940), a Belgian chemist

Toxic Gases

Refrigerators, freezers, and air conditioners have had a major impact

on the way people live and work in the twentieth century.With

them, people can live more comfortably in hot and humid areas,

and a great variety of perishable foods can be transported and

stored for extended periods. As recently as the early nineteenth century,

the foods most regularly available to Americans were bread

and salted meats. Items now considered essential to a balanced diet,

such as vegetables, fruits, and dairy products, were produced and

consumed only in small amounts.





Through the early part of the twentieth century, the pattern of

food storage and distribution evolved to make perishable foods

more available. Farmers shipped dairy products and frozen meats

to mechanically refrigerated warehouses. Smaller stores and most

American households used iceboxes to keep perishable foods fresh.

The iceman was a familiar figure on the streets of American towns,

delivering large blocks of ice regularly.

In 1930, domestic mechanical refrigerators were being produced

in increasing numbers. Most of them were vapor compression machines,

in which a gas was compressed in a closed system of pipes

outside the refrigerator by a mechanical pump and condensed to a liquid. The liquid was pumped into a sealed chamber in the refrigerator

and allowed to evaporate to a gas. The process of evaporation

removes heat from the environment, thus cooling the interior of the

refrigerator.

The major drawback of early home refrigerators involved the

types of gases used. In 1930, these included ammonia, sulfur dioxide,

and methyl chloride. These gases were acceptable if the refrigerator’s

gas pipes never sprang a leak. Unfortunately, leaks sometimes

occurred, and all these gases are toxic. Ammonia and sulfur

dioxide both have unpleasant odors; if they leaked, at least they

would be detected rapidly. Methyl chloride however, can form a

dangerously explosive mixture with air, and it has only a very faint,

and not unpleasant, odor. In a hospital in Cleveland during the

1920’s, a refrigerator with methyl chloride leaked, and there was a

disastrous explosion of the methyl chloride-air mixture. After that,

methyl chloride for use in refrigerators was mixed with a small

amount of a very bad-smelling compound to make leaks detectable.

(The same tactic is used with natural gas.)

Three-Day Success

General Motors, through its Frigidaire division, had a substantial

interest in the domestic refrigerator market. Frigidaire refrigerators

used sulfur dioxide as the refrigerant gas. Charles F. Kettering,

director of research for General Motors, decided that Frigidaire

needed a new refrigerant gas that would have good thermal properties

but would be nontoxic and nonexplosive. In early 1930, he sent

Lester S. Keilholtz, chief engineer of General Motors’ Frigidaire division,

to Thomas Midgley, Jr., a mechanical engineer and selftaught

chemist. He challenged them to develop such a new gas.

Midgley’s associates, Albert Henne and Robert McNary, researched

what types of compounds might already fit Kettering’s specifications.

Working with research that had been done by the Belgian

chemist Frédéric Swarts in the late nineteenth and early twentieth

centuries, Midgley, Henne, and McNary realized that dichlorodifluoromethane

would have ideal thermal properties and the right

boiling point for a refrigerant gas. The only question left to be answered

was whether the compound was toxic.

The chemists prepared a few grams of dichlorodifluoromethane

and put it, along with a guinea pig, into a closed chamber. They

were delighted to see that the animal seemed to suffer no ill effects

at all and was able to breathe and move normally. They were briefly

puzzled when a second batch of the compound killed a guinea pig

almost instantly. Soon, they discovered that an impurity in one of

the ingredients had produced a potent poison in their refrigerant

gas. A simple washing procedure completely removed the poisonous

contaminant.

This astonishingly successful research project was completed in

three days. The boiling point of dichlorodifluoromethane is -5.6 degrees

Celsius. It is nontoxic and nonflammable and possesses excellent

thermal properties. When Midgley was awarded the Perkin

Medal for industrial chemistry in 1937, he gave the audience a

graphic demonstration of the properties of dichlorodifluoromethane:

He inhaled deeply of its vapors and exhaled gently into a jar

containing a burning candle. The candle flame promptly went out.

This visual evidence proved that dichlorodifluoromethane was not

poisonous and would not burn.

Impact

The availability of this safe refrigerant gas, which was renamed

Freon, led to drastic changes in the United States. The current patterns

of food production, distribution, and consumption are a direct

result, as is air conditioning. Air conditioning was developed early

in the twentieth century; by the late 1970’s, most American cars and

residences were equipped with air conditioning, and other countries

with hot climates followed suit. Consequently, major relocations

of populations and businesses have become possible. Since

World War II, there have been steady migrations to the “Sun Belt,”

the states spanning the United States from southeast to southwest,

because air conditioners have made these areas much more livable.

Freon is a member of a family of chemicals called “chlorofluorocarbons.”

In addition to refrigeration, it is also used as a propellant

in aerosols and in the production of polystyrene plastics. In 1974,

scientists began to suspect that chlorofluorocarbons, when released

into the air, might have a serious effect on the environment. They

speculated that the compounds might migrate into the stratosphere,

where they could be decomposed by the intense ultraviolet light

from the sunlight that is prevented from reaching the earth’s surface

by the thin but vital layer of ozone in the stratosphere. In the process,

large amounts of the ozone layer might also be destroyed—

letting in the dangerous ultraviolet light. In addition to possible climatic

effects, the resulting increase in ultraviolet light reaching the

earth’s surface would raise the incidence of skin cancers. As a result,

chemical manufacturers are trying to develop alternative refrigerant

gases that will not harm the ozone layer.