Tefé

Tefé (Teffé in early accounts) is a municipality in the state of Amazonas, northern Brazil. It is located about 525 km by air or 595 km by river to the west of Manaus on the south bank of the Rio Solimões (the upper Amazon), on the lake formed by the mouth of the Tefé River. The nearest large city is Coari, 192 km SE by east of Tefé.

Tefé is the largest town and commercial center of the middle Solimões region. Its population was 61,453 (IBGE 2010) evenly divided between urban and rural, and its area is 23,704 km². There are no roads into Tefé and the only access is by river boat or plane. By fast boat it is about 12 hours from Manaus. TRIP Linhas Aereas operate flights from Manaus to Tefé Airport.

The city is the home of the Territorial Prelature of Tefé. Tefé is also the major starting point for trips into the Mamiraua Reserve.

History

As early as 1620 the Portuguese Carmelites could already boast of converts among the Muras, those natives of the Amazon established around Lake Teffé and on the borders of the neighbouring rivers. Tefé, also called Ega at one time, was the fourth of eight aldeias founded by Carmelite missionaries between 1697 and 1751 along the Solimões and Negro Rivers. In 1759 the commandant Joaquim de Mello da Povoas converted the Carmelite mission on Lake Tefé into a town, which he named Ega; it was elevated to a city named Tefé in 1855 (but was known as Tefé before that time). The mission, called Parauarí, was originally established on Ilha dos Veados three leagues from the location on the opposite shore of Lake Tefe, called today by the name of Nogueira. The survivors were taken to its present site by F. Andre da Costa in 1817. It was abandoned due to a smallpox outbreak in the early 18th century and moved across the lake, where it remains today.

Tef

Tef or TEF may refer to:

Teaching Excellence Framework, a UK Government initiative

Tellurium hexafluoride

Tellurium hexafluoride is a chemical compound of tellurium and fluorine with the chemical formula TeF₆. It is a colorless, highly toxic gas with an extremely unpleasant smell.

Preparation

Tellurium hexafluoride is most commonly prepared by passing fluorine gas over tellurium at 150 °C. Below this temperature a mixture of lower fluorides form, including tellurium tetrafluoride and ditellurium decafluoride. It can also be prepared by passing fluorine gas over TeO₃ or indirectly by reacting TeO₂ with SeF₄ to produce TeF₄ and then heating TeF₄ in excess of 200 °C to make TeF₆ and Te.

Properties

Tellurium hexafluoride is a highly symmetric octahedral molecule. Its physical properties resemble the sulfur and selenium analogs. It is less volatile, however, due to the increase in molecular weight. At temperatures below −38 °C, tellurium hexafluoride condenses to a volatile white solid.

Reactivity

Unlike the sulfur analog, tellurium hexafluoride is not chemically inert. This can be attributed to the larger atomic radius which can co-ordinate a maximum of eight atoms rather than six for sulfur and selenium which allows for nucleophilic attack. TeF₆ is hydrolyzed in water to Te(OH)₆ and reacts with Te below 200 °C.