Chemistry
The open "Sigrees" or coal stoves often require fanning to sustain burning because of

Interrupted release of moisture from the material
Tendency of carbon dioxide to form a layer along with dust smoke
Lack of oxygen in the surroundings of sigrees
Accumulation of smoke and dust over the sigrees

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Chemistry
Aqua regia is a 1 : 3 mixture, by volume, of

Conc. hydrochloric acid and conc. nitric acid
Conc. nitric acid and conc. hydrochloric acid
Conc. sulphuric acid and conc. nitric acid
Conc. nitric acid and conc. sulphuric acid

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