Anhydrite
CaSO4 a natural calcium sulphate usually occurring as compact granular masses and resembling marble in appearance. Differs from gypsum in hardness and lack of hydration.

Anhydrous
being without water, especially water of crystallization.

Anhydrous sodium sulphate
Na2­SO4, watersoluble, white crystals with bitter, salty taste; melts at 888°C; used in the manufacture of glass, paper, pharmaceuticals, and textiles, and as an analytical reagent.

Antimalarials
the drugs which are used to treat malaria e.g., quinine, camaquine, pamaquine etc.

Anode
refers to the electrode that is at a positive potential in electrolysis with respect to the cathode in any electrical system, such as a discharge tube or electronic device, the anode is the terminal at which electrons flow out of the system.

Anthracene
(C14H10), a white crystalline solid used extensively in the manufacture of dyes. An thracene is found in the heavy-and green-oil fractions of crude oil and is obtained by fractional crystallization. Its structure is benzene-like, having three six-membered rings fused together. The reactions are characteristic of aromatic compounds.

Antichlor
substance used to remove chlorine from materials after bleaching e.g., sodium thiosulphate (Na2S2O3).