A proportion used in determining the dimensional relationship of a representation to that which it represents: a world map with a scale of 1:4,560,000. b. A calibrated line, as on a map or an architectural plan, indicating such a proportion.
Yttria (yttrium oxide, Y 2 O 3), was discovered by Johann Gadolin in 1794 in a mineral called gadolinite from Ytterby. Ytterby is the site of a quarry in Sweden which contains many unusual minerals containing erbium, terbium, and ytterbium as well as yttrium.
Yttrium is usually found only in two different kinds of ores. The use of yttrium is still growing, due to the fact that it is suited to produce catalysers and to polish glass. Yttrium is mostly dangerous in the working environment, due to the fact that damps and gasses can be inhaled with air.