Scheele, the discoverer of oxygen, obtains a greenish-yellowish gas from hydrochloric acid and powdered black manganese dioxide in 1774, but fails to recognize it as an element.

Called oxymuriatic acid, now known to be chlorine, it is considered an oxygen-containing compound.

Digestion of bones with nitric or sulfuric acid forms phosphoric acid, from which Scheele distills phosphorus by heating with charcoal.

Scheele and Torbern Olaf Bergman recognize manganese as an element while working with the mineral pyrolusite; Scheele's associate Gahn isolates the pure metal later in 1774.

The element's name, which Guyton de Morveau will propose in 1787, derives from Latin magnes, magnet, because of earlier confusion with magnetic ores.

Scheele finds that the mineral called heavy spar or barys—Greek for heavy—contains a new earth, which becomes known as baryta.

From this base, now known to be the oxide of barium, he prepares some crystals of barium sulfate, which he sends to Gahn.

Gahn finds a month later that the mineral barite is also composed of barium sulfate.

The days of the French Revolution and Republic see many efforts to sweep away various trappings of the ancien régime (the old feudal monarchy); some of these are more successful than others.

The new Republican government seeks to institute, among other reforms, a new social and legal system, a new system of weights and measures (which become the metric system), and a new calendar.

Amid nostalgia for the ancient Roman Republic, the theories of the Enlightenment are at their peak, and the devisers of the new systems look to nature for their inspiration.

Natural constants, multiples of ten, and Latin as well as Ancient Greek derivations form the fundamental blocks from which the new systems are built.

The new calendar is created by a commission under the direction of the politician Charles-Gilbert Romme seconded by Claude Joseph Ferry and Charles-François Dupuis.

They associate with their work the chemist Louis-Bernard Guyton de Morveau, the mathematician and astronomer Joseph-Louis Lagrange, the astronomer Joseph Jérôme Lefrançois de Lalande, the mathematician Gaspard Monge, the astronomer and naval geographer Alexandre Guy Pingré, and the poet, actor and playwright Fabre d'Églantine, who invented the names of the months, with the help of André Thouin, gardener at the Jardin des Plantes of the Muséum National d'Histoire Naturelle in Paris.

As the rapporteur of the commission, Charles-Gilbert Romme presents the new calendar to the Jacobin-controlled National Convention on September 23, 1793, which adopts it on October 24, 1793, and also extends it proleptically to its epoch of September 22, 1792.

It is because of his position as rapporteur of the commission that the creation of the republican calendar is attributed to Romme.

The calendar is often called the "French Revolutionary Calendar" because it is created during the Revolution, but this is somewhat of a misnomer.

Indeed, there was initially a debate as to whether the calendar should celebrate the Great Revolution, which began in July 1789, or the Republic, which was established in 1792.

Immediately following July 14, 1789, papers and pamphlets started calling 1789 year I of Liberty and the following years II and III.

It was in 1792, with the practical problem of dating financial transactions, that the legislative assembly had been confronted with the problem of the calendar.

Originally, the choice of epoch was either January 1, 1789 or July 14  1789.

After some hesitation the assembly had decided on January 2, 1792 that all official documents will use the "era of Liberty" and that the year IV of Liberty had started on January 1, 1792.

This usage had been modified on September 22 , 1792 when the Republic was proclaimed and the Convention decided that all public documents would be dated Year I of the French Republic.

The decree of January 2, 1793 had stipulated that the year II of the Republic began on January 1, 1793; this is revoked with the introduction of the new calendar, which sets September 22, 1793, as the beginning of year II.

The establishment of the Republic is used as the epochal date for the calendar; therefore, the calendar commemorates the Republic, not the Revolution.

In France, it is known as the calendrier républicain as well as the calendrier révolutionnaire.