Can they pose a danger to people's health?
In sodium cyanide's case - yes, very much so. US government health experts say it can be "rapidly fatal" if inhaled or ingested. It is soluble in water - raising concerns in some Chinese media that it may have entered drain water - but its dust is also easy to inhale.
It releases the highly poisonous gas hydrogen cyanide when dissolved or burned.
Potassium nitrate can cause breathing problems and damage to kidneys, while ammonium nitrate can be toxic when burned.
Calcium carbide can be harmful if touched or breathed, and doctors recommend immediately washing affected areas.
One image widely circulated on the Chinese micro-blogging site Weibo, said to be from the disaster site, appeared to show a chemical burning when water was poured on it.
"With such a large fire, inevitably the plume of toxic fumes that have been dispersed could have devastating effects to the public in the future," says Shane O'Carroll, a chemical safety specialist with Chemstore, a British hazardous materials company.
Mr O'Carroll says sodium cyanide running off into groundwater systems could pose a public health risk, and he said people in Tianjin should consider drinking only bottled water.