40 Fun Facts About Sodium Hydroxide

Which Nordic Christmas dish of dried cod is soaked in lye, such as sodium hydroxide, to give a jelly-like texture?

Lutefisk literally means lye fish, and the cured cod is so caustic that it needs several more days in fresh cold water before anyone can eat it.

Which German bakery classic gets its glossy brown crust from a dip in sodium hydroxide solution before baking?

Pretzel dough gets its dark skin and flavor from the lye dip, which drives Maillard browning as it bakes, and German bakers treat rolls and croissants the same way.

In which Brad Pitt film does a soap maker pour lye on another man's hand to cause a chemical burn?

Fight Club has Tyler Durden kiss the narrator's hand before pouring on the lye, and the cast took soapmaking lessons to prepare for their roles.

Which bitter Mediterranean fruit is often soaked in sodium hydroxide so that curing takes days instead of months?

Olives straight from the tree are too bitter to eat because of a compound called oleuropein, and lye strips it out in a few days where other cures take months.

Which American household product, invented in 1923, combines sodium hydroxide crystals with shards of aluminum?

Drano fizzes in a wet pipe because the metal reacts with the lye, and the bubbling stirs the mix while the lye turns greasy clogs into soap.

Which flammable gas builds up when sodium hydroxide touches aluminum, as happened inside a British road tanker in 1986?

Hydrogen is released as the metal dissolves, and in 1986 it pressurized a tanker that had been loaded with sodium hydroxide solution by mistake.

Which Chinese preserved delicacy, set into dark jelly by sodium hydroxide, is wrongly said to be soaked in horse urine?

Century egg curing works by slowly raising the pH inside the shell to as high as 12, and the horse rumor may owe something to the smell of ammonia.

Whose autobiography describes getting his first conk, a hairstyle made by combing burning lye through the hair?

Malcolm X later condemned the conk as degrading, and the homemade lye gel, often mixed with potatoes, could burn the scalp badly if it stayed on too long.

Soaking the dried kernels of which grain in lye produces hominy, the starting point for Southern grits?

Corn soaked in lye sheds its tough hulls and softens, and the treatment also frees the vitamin niacin so the body can absorb it.

Food factories dip fruits and vegetables in sodium hydroxide solution to carry out which step before canning?

Peeling by chemical bath is one of several food jobs for sodium hydroxide, which also helps process cocoa, color caramel and thicken ice cream.

Which English chemist first isolated sodium metal in 1807 by passing an electric current through molten caustic soda?

Humphry Davy went on to isolate calcium, barium and magnesium the following year, using electricity to pull apart compounds nobody had managed to split.

Factories that make sodium hydroxide by electrolysis also turn out which gas, widely used to disinfect drinking water?

Chlorine and sodium hydroxide leave the cell in fixed proportions, so producers have to find buyers for both products at the same time.

Sodium hydroxide neutralizes which acid, also found in the human stomach, to leave only table salt and water?

Hydrochloric acid and sodium hydroxide cancel each other so neatly that teachers use the pair to show students the two ends of the pH scale.

Which color does the indicator phenolphthalein turn when a few drops of sodium hydroxide make a solution basic?

Pink appears once the solution turns basic, above a pH of about 8, yet in very strong sodium hydroxide the color slowly fades away again.

The Na in sodium hydroxide's formula comes from natron, a natural mineral salt harvested in which ancient land?

Egypt's natron inspired the Neo-Latin name natrium, which the Swedish chemist Berzelius shortened to Na in his 1814 system of atomic symbols.

Dilute sodium hydroxide gives fingers which telltale feeling as it converts the skin's natural oils into soap?

Slippery fingers mean the chemical is already reacting with the skin, a soap-forming process that chemists call saponification.

Hard bar soap is made with sodium hydroxide, but liquid soaps usually rely on the hydroxide of which other metal?

Potassium hydroxide gives softer soaps that dissolve more easily, while sodium hydroxide is the cheaper of the two and less of it is needed.

Solid sodium hydroxide must be kept in airtight containers because it absorbs moisture and which gas from the air?

Carbon dioxide and moisture both spoil the chemical, and a pellet left in open air soaks up so much water vapor that it dissolves itself.

Which common laboratory material is slowly attacked by sodium hydroxide, causing joints and stopcocks to seize up?

Glass slowly dissolves into soluble silicates, so hot sodium hydroxide leaves flasks frosted and the chemical is usually stored in plastic or steel.

One of the biggest industrial uses of sodium hydroxide is turning wood into which everyday material?

Paper mills cook wood chips in sodium hydroxide to dissolve lignin, the natural glue that holds the cellulose fibers together.

The Bayer process cooks which ore in hot sodium hydroxide solution to extract the raw material for aluminum?

Bauxite dissolves only in part, so the alumina goes into solution while the iron oxides stay behind as a caustic waste known as red mud.

In 1844 John Mercer found that sodium hydroxide makes which natural fiber stronger and far easier to dye?

Cotton treated this way is still called mercerized, though the silky shine sold today came decades later, when Horace Lowe added tension.

Which fabric, long sold as artificial silk, is made by treating wood pulp with sodium hydroxide?

Rayon starts as pulp steeped in caustic soda, which is later dissolved into a syrup called viscose and forced through a spinneret to make filaments.

Sodium hydroxide acts as the catalyst when vegetable oil and methanol are turned into which alternative fuel?

Biodiesel makers must keep the mix dry, because sodium hydroxide combined with water would turn the oil into soap instead of fuel.

Sodium hydroxide is the grease-dissolving ingredient in many spray cleaners made for which kitchen appliance?

Oven cleaners rely on lye to break baked-on grease into residues that wash off, the same chemistry that drain openers use on clogs.

Water utilities add sodium hydroxide to raise pH so that less of which toxic metal dissolves from old pipes?

Lead and copper dissolve less readily once the pH goes up, so the same chemical that unclogs drains also helps keep tap water safe.

Stirring sodium hydroxide pellets into water has which dramatic effect on the solution, a known hazard for soap makers?

It heats up so sharply that adding the pellets too quickly can make the mixture boil or erupt, a kind of reaction chemists call exothermic.

A recipe for sodium hydroxide appears in a late-1200s Arab book on soap making compiled by a king of which country?

Yemen's King al-Muzaffar Yusuf compiled the book, whose recipe ran water again and again through plant ash and quicklime to draw out the caustic liquid.

Which French chemist patented a 1791 method for making soda ash, the raw material for early caustic soda?

Nicolas Leblanc was never paid the prize money he had earned, and revolutionaries later seized his factory and published his trade secrets.

The Castner–Kellner process made sodium hydroxide in cells built around an electrode of which toxic metal?

Mercury from one such plant in Ontario, Canada, poisoned river fish and the people who ate them, a reason mercury cells have largely given way to membrane cells.

Trafigura's 2006 waste from washing fuel with sodium hydroxide was dumped in which West African country?

Ivory Coast later received about $198 million from the company toward the cleanup, after the ship had reportedly been turned away by several other countries.

A reservoir of caustic red mud, left by refining aluminum ore with sodium hydroxide, burst in 2010 in which country?

Hungary saw about a million cubic meters of the sludge escape near the town of Ajka, killing ten people and reaching the Danube within days.

Adding sodium hydroxide to a solution of copper sulfate produces a solid precipitate of which color?

Blue copper hydroxide drops out because it cannot dissolve, a trick chemists use to identify metals, since iron gives green or brown solids instead.

Which lab technique drips sodium hydroxide from a burette into an acid to measure the acid's exact concentration?

Titration owes its convenient modern burette to the German chemist Karl Friedrich Mohr, who also wrote the first textbook on the method in 1855.

A sodium hydroxide solution was traditionally the most common way to strip what from old wooden furniture?

Paint lifts off after a caustic soak, but the method fell out of favor because it raises the grain and stains the wood underneath.

Sodium hydroxide lye keeps poultry scalding tanks sanitary and also helps to remove what from the chickens?

Feathers come away more easily after a lye scald, a side benefit of what processors chose mainly as a cheap way to keep the tanks clean.

What is the standard first aid when sodium hydroxide lands on skin, kept up for at least ten minutes?

Flush with water straight away, because even a dilute solution keeps breaking down the proteins in skin until it is washed off, and eye splashes can blind.

In kraft pulp mills, the hot blend of sodium hydroxide and sodium sulfide that cooks wood chips has which name?

White liquor leaves the digester as black liquor, darkened by dissolved lignin, and mills burn that brew to recover the chemicals for reuse.

Which country's steamed rice cake kutsinta gets a jelly-like chew from a small amount of lye water?

The Philippines eats kutsinta year-round as a snack, traditionally topped with freshly grated coconut.

Lye water is an essential ingredient in the crust of which Chinese pastry eaten at the Mid-Autumn Festival?

Mooncake crusts depend on lye water, and the same ingredient gives many Chinese noodles their yellow color.