Maximum permissible turbidity in potable water is ________ ppm?

Coal tar (produced by high temperature carbonization) is the main source of________?

Which one can be directly solidified from gaseous state without entering into liquid state?

The equation relating friction factor to Reynold number, f-0.5 = 4 loge (NRe/√f)-0.4, is called the ________ equation?

When the solvent dissolves very little of solute, then________?

Coke oven gas burns with a yellowish flame, because of the presence of ________?