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The only hydrates with stable melting points are NaOH·H 2 O (65.10 °C) and NaOH·3.5H 2 O (15.38 °C). The other hydrates, except the metastable ones NaOH·3H 2 O and NaOH·4H 2 O (β) can be crystallized from solutions of the proper composition, as listed above. However, solutions of NaOH can be easily supercooled by many degrees, which ...
Many of them are hygroscopic. Organic compounds. Chemical formula Name CAS number CH 3 CHO: acetaldehyde: 75-07-0 CH 3 CO 2 H: acetic acid: 64-19-7 (CH 3) 2 CO ...
Such materials were then said to be hygroscopic because they were suitable for making a hygroscope. Eventually, the word hygroscope ceased to be used for any such instrument in modern usage, but the word hygroscopic (tending to retain moisture) lived on, and thus also hygroscopy (the ability to do so).
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
Soda lime canister used in anaesthetic machines to act as a carbon dioxide scrubber. Soda lime, a mixture of sodium hydroxide (NaOH) and calcium oxide (CaO), is used in granular form within recirculating breathing environments like general anesthesia and its breathing circuit, submarines, rebreathers, and hyperbaric chambers and underwater habitats.
Similarly, potassium hydroxide is available as a solution used for cleaning terraces and other areas made out of wood. Both NaOH and KOH are also used in the production of soap and detergents (saponification). Due to their hygroscopic properties, alkali hydroxides are used as desiccants.
Without the presence of dissolved NaOH or KOH, responsible for the high pH (~13.5) of the concrete pore water, the amorphous silica of the reactive aggregates would not be dissolved and the reaction would not evolve. Moreover, the soluble sodium or potassium silicate is very hygroscopic and swells when it absorbs water.
Sodium nitrate reacts with hydrogen gas: Na + + NO 3 − + 4H 2 → NaOH + NH 3 + 2H 2 O. This removes hydrogen, which poses a fire and explosion hazard and produces ammonia, which is also capable of decomposing organic material, albeit less aggressively than lye. The sodium hydroxide (lye) is consumed by further action of the first reaction.