Hydrogen peroxide is a chemical compound with the formula H2O2. In its pure form, it is a pale blue, clear liquid more viscous than water. Hydrogen peroxide is the simplest peroxide, it is used as an oxidizer, bleaching agent, antiseptic. Concentrated hydrogen peroxide, or "high-test peroxide", is a reactive oxygen species and has been used as a propellant in rocketry, its chemistry is dominated by the nature of its unstable peroxide bond. Hydrogen peroxide is unstable and decomposes in the presence of light; because of its instability, hydrogen peroxide is stored with a stabilizer in a weakly acidic solution in a dark coloured bottle. Hydrogen peroxide is found in biological systems including the human body. Enzymes that use or decompose hydrogen peroxide are classified as peroxidases; the boiling point of H2O2 has been extrapolated as being 150.2 °C 50 °C higher than water. In practice, hydrogen peroxide will undergo explosive thermal decomposition if heated to this temperature, it may be safely distilled at lower temperatures under reduced pressure.

Hydrogen peroxide is a nonplanar molecule with C2 symmetry. Although the O−O bond is a single bond, the molecule has a high rotational barrier of 2460 cm−1; the increased barrier is ascribed to repulsion between the lone pairs of the adjacent oxygen atoms and results in hydrogen peroxide displaying atropisomerism. The molecular structures of gaseous and crystalline H2O2 are different; this difference is attributed to the effects of hydrogen bonding, absent in the gaseous state. Crystals of H2O2 are tetragonal with the space group D44P4121. In aqueous solutions hydrogen peroxide differs from the pure substance due to the effects of hydrogen bonding between water and hydrogen peroxide molecules. Hydrogen peroxide and water form a eutectic mixture, exhibiting freezing-point depression down as low as -56°C; the boiling point of the same mixtures is depressed in relation with the mean of both boiling points. It occurs at 114 °C; this boiling point is 14 °C greater than that of pure water and 36.2 °C less than that of pure hydrogen peroxide.

Hydrogen peroxide has several structural analogues with Hm−X−X−Hn bonding arrangements. It has the highest boiling point of this series, its melting point is fairly high, being comparable to that of hydrazine and water, with only hydroxylamine crystallising more indicative of strong hydrogen bonding. Diphosphane and hydrogen disulfide exhibit only weak hydrogen bonding and have little chemical similarity to hydrogen peroxide. All of these analogues are thermodynamically unstable. Structurally, the analogues all adopt similar skewed structures, due to repulsion between adjacent lone pairs. Alexander von Humboldt synthesized one of the first synthetic peroxides, barium peroxide, in 1799 as a by-product of his attempts to decompose air. Nineteen years Louis Jacques Thénard recognized that this compound could be used for the preparation of a unknown compound, which he described as eau oxygénée – subsequently known as hydrogen peroxide. Today this term refers instead to water containing dissolved oxygen.

An improved version of Thénard's process used hydrochloric acid, followed by addition of sulfuric acid to precipitate the barium sulfate byproduct. This process was used from the end of the 19th century until the middle of the 20th century. Thénard and Joseph Louis Gay-Lussac synthesized sodium peroxide in 1811; the bleaching effect of peroxides and their salts on natural dyes became known around that time, but early attempts of industrial production of peroxides failed, the first plant producing hydrogen peroxide was built in 1873 in Berlin. The discovery of the synthesis of hydrogen peroxide by electrolysis with sulfuric acid introduced the more efficient electrochemical method, it was first implemented into industry in 1908 in Weißenstein, Austria. The anthraquinone process, still used, was developed during the 1930s by the German chemical manufacturer IG Farben in Ludwigshafen; the increased demand and improvements in the synthesis methods resulted in the rise of the annual production of hydrogen peroxide from 35,000 tonnes in 1950, to over 100,000 tonnes in 1960, to 300,000 tonnes by 1970.

Pure hydrogen peroxide was long believed to be unstable, as early attempts to separate it from the water, present during synthesis, all failed. This instability was due to traces of impurities, which catalyze the decomposition of the hydrogen peroxide. Pure hydrogen peroxide was first obtained in 1894—almost 80 years after its discovery—by Richard Wolffenstein, who produced it by vacuum distillation. Determination of the molecular structure of hydrogen peroxide proved to be difficult. In 1892 the Italian physical chemist Giacomo Carrara determined its molecular mass by freezing-point depression, which confirmed that its molecular formula is H2O2. At least half a dozen hypothetical molecular structures seemed to be consistent with the available evidence. In 1934, the English mathematical physicist William Penney and the Scottish physicist Gordon Sutherland proposed a molecular structure for hydrogen peroxide, similar to the presently accepted one. Hydrogen peroxide was prepared industrially by hydrolysis of ammonium persulf

Marejada is one of the most popular national Brazilian celebrations in Itajaí city, Santa Catarina state. This celebration commemorates the first disembarkation of European people from Portugal to the Brazilian coast. Marejada calling from word “mar” and can be translated as Portugalization; the festival celebrates sea food—fishing is one of the main economic activities of Itajaí regions. The main food on this fiesta is sea food and the main drink is beer—it is why this fiesta looking like beer makers celebrate; this fiesta is folklore of Brazil. Symbols of Marejada—fish in cap and human face playing accordion, shrimps on the plate, one glass of beer, dancing group in national clothes—are painted on the souvenir plate from Marejada fiesta. You can read on the souvenir plates the following: FESTA PORTUGUESA E DO PESCADO – Celebrate of Portugalization and Fishing. ITAJAI SC - Itajai Santa Catarina. Marejada is celebrated every year in October from 1987. For example, this fiesta took place from 8 to 18 October 2009.

Due to anniversary of Portugalization it was from 8 to 24 October 2010. There are 600 attractions in a physical space of 36 thousand square meters. In the main pavilion, the night dances gather thousands of people every night. Governo Municipal de Itajaí

The Queen of Swords is a card in the Suit of Swords, part of the Minor Arcana set of the Tarot. Tarot cards are used throughout much of Europe to play tarot card games. In English-speaking countries, where the games are unknown, Tarot cards came to be utilized for divinatory purposes, she is extending her hand to reach for another. The PKT says she is familiar with sorrow, so it may be understood in this way, her crown is made up of butterflies, showing the freedom of her active intellect. Note the difference between the pristine white clouds, the darker ones showing up on the right bottom corner; the latter ones may reflect upon her sorrows. The former - the unusual clarity of her mind and thoughts. Compare with other sword court cards, where the clouds are tarnished; the hand in front signifies putting thoughts into action. All the sword cards represent the mind and the element of air all the skyscapes will indicate the "emotion" of the card; this one with clouds low on the horizon mean new ideas or a new enterprise