Dry cell
Refers to a voltaic cell in which the electrolytic is in the form of a jelly or paste. The Leclanche dry cell is extensively used for flashlights and other portable applications.

Dry ice
Carbon dioxide in the solid form, usually made in blocks to be used as  a coolant; changes directly to a gas at-78.5ºC as heat is absorbed.

Ductility
The ability of a material to be plastically deformed by elongation, without fracture. A property by which materials can be drawn into wires. Silver and gold are highly ductile.

Dyestuffs
Intensely coloured compounds applied to a substrate, e.g., fibre, paper, cosmetic, hair to give colour. React by absorption, solution, bonding. Pigments retain their identity more closely on bonding to the substrate. Colours generally originate in electronic transitions; most dyestuffs are organic in nature but are frequently applied together with inorganic species. Classified in the colour index by chemical nature; also classified by their method of application as acid, basic, direct disperse, azo, sulphur, vat or fibre reactive.

Earth’s crust
A solid outer layer of the earth, the most abundant elements in earth’s crust are O, Na, Si, Al, Fe, Ca, K and Mg. They form oxides, silicates, aluminium, carbonates, sulphates which occur in various rocks.