"Lime water" technique -- why use an excess of cal?
At https://www.catsfork.com/CatsKitchen/lime-water I see a technique from a cookbook called Nourishing Traditions for soaking cornmeal in 'lime water', created from pickling lime (calcium hydroxide, aka "cal"). The technique starts by preparing a quart of lime water by adding a quart of filtered water to something like a half a cup of pickling lime powder, sharing, letting the powder settle out, and then using the water obtained by pouring the liquid portion off of the settled solids.
I am confused because according to the solubility table at https://en.m.wikipedia.org/wiki/Solubility_table, something like 2 grams of calcium hydroxide would be expected to dissolve in a quart of water. That's basically one mL of calcium hydroxide that is expected to dissolve; why would you use a half cup (which is approximately a hundred times that amount)?
Am I missing something about the technique? Is there a reason why using a dramatic surplus might be anything other than wasteful?
Best Answer
The supersaturation of cal seems to be the common instruction in most online sources, but no reason is given. The best reason seems to come from chemistry texts, which note:
Ca(OH)2 is only slightly soluble in water (0.16g Ca(OH)2/100g water at 20°C) forming a basic solution called lime water. The solubility decreases with increasing temperature. The suspension of calcium hydroxide particles in water is called milk of lime.
According to Cook's Illustrated, you are trying to get as much lime into the water as you can, since your target is an extremely alkaline (pH 12.4) solution. So .. if it's hard to dissolve Ca(OH)2, and you're going for maximum saturation, dump a whole bunch in and pour off the solution.
Pictures about ""Lime water" technique -- why use an excess of cal?"
What happens when lime water is blown in excess?
When passed in excess amount, the calcium carbonate formed further reacts with carbon dioxide and water to form calcium hydrogen carbonate [Ca(HCO3)2], which is colorless solution. Hope this helps!!What is the purpose of lime water in an experiment?
Limewater can be used to detect carbon dioxide. If carbon dioxide is bubbled through limewater then it turns from clear to cloudy/milky in colour. This is why limewater used in a simple respirometer can show that more carbon dioxide is present in exhaled air compared to inhaled air.What is lime water Why is it used for testing carbon dioxide?
Lime Water Test: Limewater is basically a solution of calcium hydroxide. So if we bubble carbon dioxide through the solution it reacts with calcium hydroxide solution to produce a white precipitate of calcium carbonate. We will observe that the limewater will turn milky or cloudy white.How does the use of lime water remove the hardness of water?
The water is treated with lime or a combination of lime and soda ash (carbonate ion). These chemicals react with the hardness and natural alkalinity in the water to form insoluble compounds. The compounds precipitate and are removed from the water by sedimentation and, usually, filtration.Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Castorly Stock, Castorly Stock, Teona Swift, Teona Swift