Chlorocarbon Compounds

Since Ancient times, ice had been used to keep things cool, until around the mid-nineteenth century, when refrigerants began to go into use.  Refrigeration is the process by which a refrigerant undergoes an evaporaration-compression cycle, absorbing the heat within a system.  In 1877, a cargo of frozen beef was successfully shipped aboard the S.S. Paraguay from Argentina to France, using the refrigeration process for the first time ever.  This marked a milestone in the refrigeration industry, and also opened up new opportunities for trade, allowing goods that needed to be kept frozen or chilled to be transported over longer distances.  The primary refrigerants used back in the 1800s were ether, ammonia, methyl chloride, and sulfur dioxide, and though they were good refrigerants, they either decomposed, were fire hazards, were poisonous, or smelled terrible.  By the early 20th century, compounds called chlorofluorocarbons (CFCs) replaced the older, less efficient refrigerants, and were seemingly perfect for the job.  But CFCs are carbon-based molecules that include chlorine, flourine, and occasionally hydrogen atoms.  It is the chlorine in these that was eventually found to cause major problems with the ozone layer, and CFCs were soon after banned from use in most countries.  The ozone layer is made of gaseous oxygen atoms, oxygen molecules (O2), and ozone molecules (O3) that are constantly reacting with one another, but keep a balance between these reactions.  The chlorine atoms that arise from the CFCs also react with the ozone layer, but upset the natural balance as they break down ozone molecules but do not reform them.  When there are disturbances within the ozone layer, harmful rays from the Sun that are ussually kept out by the layer, enter the atmosphere and cause considerable damage.  Today, other chlorine-containing compounds that are not harmful to the environment are used as refrigerants and in other systems.

Chlorocarbons have also been used in a variety of other settings, such as in the fields as a pesticide, and in the operating room as anesthetics.  Molecules such as dichloro-diphenyl-trichloroethane, or DDT, have been used extensively as pesticides, but later went out of use as it killed helpful insects as well as harmful ones, and also caused human health issues.  Another chlorocarbon, hexachlorophene, was used in many germicide products in the 1950s, but also followed in the steps of DDT as it was soon found to be toxic.  As an anesthetic, chlorocarbons also seemed to be ideal for the job, but they were also eventually found to have harmful effects on the body as well.  Though most chlorocarbons have been proven to be very harmful to the human body and to the environment, they have also shaped the course of history, having first applied refrigeration in the real world and introducing man to the use of anesthetics among other things.