Arsenic
(symbol As, at. wt. 75, sp. gr. 5.76), a metallic element of very common occurrence, being found in combination with many of the metals in a variety of minerals. It is of a dark gray color, and readily tarnishes on exposure to the air, first changing to yellow, and finally to black. In hardness it equals copper; it is extremely brittle, and very volatile, beginning to sublime before it melts. It burns with a blue flame, and emits a smell of garlic. It forms alloys with most of the metals. Combined with sulphur it forms orpiment and realgar, which are the yellow and red sulphides of arsenic. Orpiment is the true arsenicum of the ancients. With oxygen arsenic forms two compounds, the more important of which is arsenious oxide or arsenic trioxide (As2O₂) which is the white arsenic or simply arsenic of the stores. It is used as a flux for glass, and also for forming pigments. The arsenite of copper (Scheele's green) and a double arsenite and acetate of copper (emerald green) are largely used by painters; they are also used to color paper hangings for rooms. Arsenic has been too frequently used to give that bright green often seen in colored confectionery.
ARSINOË (ar-sin'ō-ē), a city of ancient Egypt, on Lake Meris, said to have been founded about B. c. 2,300, but re- 279, she married her own brother, Ptolemy II. Philadelphus.