General Science Quiz: Industrial Chemistry: Glass, Cement, Fertilisers and Explosives

Superphosphate of lime is made by treating rock phosphate with sulphuric acid, and the nutrient it supplies is phosphorus in the form of available phosphate, not nitrogen; it is therefore a phosphatic fertiliser.

Nitrogen, phosphorus and potassium are the three primary nutrients, and a fertiliser that carries two or more of them in one chemical compound is called a complex or mixed fertiliser; diammonium phosphate, which supplies both nitrogen and phosphate, and the NPK grades sold by number are the familiar examples.

Farmyard manure is the decomposed mixture of cattle dung, urine and bedding litter, and in general it carries only about half a per cent of nitrogen, along with roughly the same order of phosphate and potash.

About two or three per cent of gypsum, which is calcium sulphate dihydrate, is ground with the clinker because it slows down the hydration of tricalcium aluminate, the compound that would otherwise set almost the moment water was added and leave no time to place the concrete.

Cement needs one calcareous material, limestone, for its lime, and one argillaceous material, clay or shale, for its silica, alumina and iron oxide; the mixture is burnt in a rotary kiln at about 1450 degrees Celsius to give clinker, which is then ground with gypsum.

Metal oxides dissolved in molten glass absorb part of the visible spectrum, and cobalt oxide is the standard colourant for the deep blue of bottles and decorative glass, effective in very small quantities.

Replacing part of the soda and lime of ordinary glass with boron trioxide gives a glass whose coefficient of thermal expansion is very low, so it does not crack when heated or cooled suddenly; that is why laboratory beakers, test tubes and ovenware are made of it.

Gun powder, also called black powder, is made of roughly seventy-five parts potassium nitrate or saltpetre, which supplies oxygen, fifteen parts charcoal, which is the fuel, and ten parts sulphur, which lowers the ignition temperature and speeds the burning.

Nobel made the dangerously sensitive liquid nitroglycerine safe to transport and use by absorbing it in kieselguhr, a porous earth, and patented the resulting dynamite in 1867; he later combined nitroglycerine with nitrocellulose to make blasting gelatin, and the fortune from these patents endowed the Nobel Prizes.

Muriate of potash is potassium chloride, carrying about sixty per cent potash, and it is the cheapest and most widely used source of potassium for crops; the old word muriate simply means a chloride.

In it nitrogen from the air and hydrogen from natural gas combine directly over a finely divided iron catalyst at high pressure and a temperature of about 450 to 500 degrees Celsius; the ammonia produced is then reacted with carbon dioxide to make urea.