Términos

Nonmetallic chemical element (H). It is a colorless, odorless, tasteless gas, the lightest chemical element, and is used in rocket fuels and balloons. Its most important compound (with oxygen) is water.

A colorless corrosive gas, the hydride of fluorine and an extremely powerful halogen acid, hydrogen fluoride is used as a catalyst and a fluorinating agent. Its chief use is in making fluorine-containing refrigerants such as freons. In a conservation context, hydrogen fluoride is considered as an atmospheric pollutant which damages metal structures, and buildings or monuments made of limestone.

Chemical elements of hydrogen having the same atomic number but different mass. Three of them are naturally occuring: 1H (protium), 2H (deuterium), and 3H (tritium).

A colorless, unstable liquid prepared in an aqueous solution for commercial use, employed as a sterilizing, oxidizing and bleaching agent.

Toxic, flammable, colorless gas that smells like rotten eggs. Hydrogen sulfide may be created by decay of organic matter or obtained as a byproduct of refining carbonaceous fuels such as natural gas, crude oil, and coal. As an atmospheric pollutant, hydrogen sulfide blackens lead pigments, and tarnishes silver.

The branch of geology which studies water on or below the surface of the earth in relation to its geologic environment.

Physical features that contain water, either natural or man-made.

A marble-like mixed-mineral stone. Its name alludes to its composition: a hydrated magnesium composite.

Family containing around 16 genera and 350 species of herbaceous plants.

Genus containing 8 species of herbaceous plants native to North America.

In some classifications, Hydropotes is considered a third subfamily of the family Cervidae, along with Old World deer (subfamily Cervinae) and New World deer (subfamily Capreolinae). This subfamily was created to contain the Chinese water deer (Hydropotes inermis), a very small Asian deer of the family Cervidae (order Artiodactyla), native to fertile river bottoms in Korea and the Yangtze River (Chang Jiang) valley in China. It is the only species of deer in which males lack antlers; instead, they are armed with long, curved, and sharp upper canine teeth that protrude from the mouth. These tusks may exceed 5 cm (2 inches) in length. The water deer is also the only deer with inguinal glands. Although water deer resemble extinct primitive deer in lacking antlers, they evolved from ancestors with antlers that were subsequently lost. Their morphology indicates that they are New World deer. Males stand about 50 cm (20 inches) tall at the shoulder and weigh up to 13 kg (29 pounds); females weigh up to 11 kg (24 pounds). They have a rather uniformly colored coat, yellowish brown above and yellowish white below. The tail is very short, and there is no rump patch. Their coarse, thick coat and fur-covered ears are adaptations to cold, snowy winters.

A neutral cellulose derivative, hydroxyethyl cellulose (HEC) is a granular, water-soluble thermoplastic polymer used as an emulsifier, thickener and film former in many types of solutions. It is also used as a sizing material.

Hydrophilic organic monomer used in the manufacture of flexible contact lenses. In conservation used as a water-absorbing poultice.

Hydroxypropyl cellulose (HPC) is a water-soluble cellulose ether used as an emulsifier, thickener, and suspending agent in many types of solutions. In conservation, HPC is used as a consolidant for leather afflicted by "red rot", and as a fixative for pigments and dyes.

Activities and principles for preserving or promoting health.

The technique accomplishing the measurement of atmospheric humidity.

Tools comprised of a conjoined hygrometer and thermograph, which record temperature and relative humidity conditions in which sensitive objects are displayed or stored.