Should your one litre bottle of orange juice be labelled 1 l or 1 L? Chemists use letters as symbols for units, such as m for metre and g for gram. They have always had the rule that units named after people are abbreviated with a capital letter and others are not. For example: The hertz (cycles per second), has the symbol Hz, because it is named after Heinrich Rudolf Hertz. However when students write one litre, it is abbreviated as 1l, which looks like eleven. So many teachers wanted to use a capital L, not a small l, as the abbreviation for litre. The word litre is from litron, an old and no longer used French unit once used for measuring grain; so litre should not be abbreviated with a capital letter.
Chemistry professor, Dr. Kenneth Woolner of the University of Waterloo decided to turn the argument into a joke. So in 1977, during a terrible Canadian snow storm, Claude Émile Jean-Baptiste Litre was brought to life by a mad scientist. Dr. Woolner invented the inventor of the litre and published a fake story about him in a newsletter for secondary school students (Chem 13 News). It was intended as a joke, but many people took it seriously and thereafter used a capital L for litre. It was taught in schools.
It was also included in the very respectable Collier's Encyclopedia.
The liter, a metric unit of volume or capacity, is named for a founding father of the metric system, Claude Emile Jean-Baptiste Litre, whose family sold wine in the first litre (liter) bottles to bear the name.
Macmillan Educational Company, New York, and P.F. Collier, Inc., London & New York (1987), Volume 16, page 69 also the 1992 edition, Volume 16, page 69.
Ten years later, in the same student newsletter Dr. Woolner confessed that his first story was a joke. Many people who had believed in Claude Litre were very upset with Dr. Woolner. Today most people will accept either a big or a small L/ l for litre. This is the story of a joke and of writing scientific terms. However it is also the story of how people copy and believe things too easily. In these internet days, remember that much of the information online might be false and should be checked.
The purpose of writing is to communicate with people, so it is best to avoid confusing them. Today both a capital L and a small l are acceptable, but the official metric unit is dm3. A dm (decimetre) is a tenth of a metre and the cube of a dm is a litre. It is more correct and traditional to use a small l for a litre and many people prefer to avoid confusion by using a different font for a small l litre symbol. Other people use the official dm3, which takes longer to write. When you can avoid using a capital L it is best to do so, but if it will be confusing use a capital L instead of a small l.