Sodium hydroxide: deliquescence

Properties oi the alkali hydroxides.—The alkali hydroxides are brittle, white, translucent solids with a more or less crystalline fracture, and fibrous texture. Sodium hydroxide deliquesces on exposure to the air, but it goes solid again owing to the formation of the carbonate by the absorption of carbon dioxide from the air. Lithium hydroxide is a little hygroscopic. Potassium hydroxide is even more deliquescent than the sodium compound but its carbonate is also deliquescent. The hydroxides are very solnble in water, and they also dissolve in alcohol. The reported numbers for the specific gravities22 of sodium hydroxide range from l-723 to 2T30 and for potassium hydroxide, from l-958 to 2 6. The best representative sp. gr. are 2"54 for lithium hydroxide 2130 for sodium hydroxide 2 044 for potassium hydroxide 3"203 (11°) for rubidium hydroxide and 3-675 (11°) for csesium hydroxide. 

Sodium hydroxide (NaOH) (caustic soda) White deliquescent solid. Sticks, flakes, pellets. Dissolution in water is highly exothermic. Strongly basic. Severe hazard to skin tissue... 

Sodium hydroxide (NaOH) (caustic soda) Potassium hydroxide (KOH) (caustic potash) Calcium hydroxide (Ca(OH)2) (slaked lime) Ammonium hydroxide (NH4OH) (aqueous ammonia solution) White deliquescent solid. Sticks, flakes, pellets. Dissolution in water is highly exothermic. Strongly basic. Severe hazard to skin tissue White deliquescent solid. Sticks, flakes, pellets. Dissolution In water is highly exothermic. Strongly basic. Severe hazard to skin tissue White powder soluble in water yielding lime water. Alkaline Weakly alkaline. Emits ammonia gas. Severe eye irritant... 

Sodium Hydroxide. NaOH mw 40.01 white deliquescent crystals, mp 318°, bp 1390°, d 2.13 sol in w, ale, glycerin acids insol in eth or acetone. Prepd by electrolysis of NaCl solns... 

Bismuth trichloride also unites with quinoline and pyridine. Quino-lino-bismuth chloride, [Bi(C9H7N)]Cl3, is obtained as a white crystalline mass on mixing the chloride with the base. This derivative is only slowly decomposed by water and is not deliquescent.3 Bismuth chloride and pyridine form a white compound of composition BiCl3.l-5(CsH5N) or 2BiCl3.3(C5H5N) on adding pyridine to an ethereal solution of bismuth chloride,4 or it may be formed from an acetone solution of the chloride and excess of pyridine.3 It is a white crystalline powder, fairly stable towards water, and only attacked slowly by hydrochloric acid. Aqueous sodium hydroxide quickly decomposes the additive compound. 

Substances that are ordinarily deliquescent are sulfuric add (concentrated), glycerol, calcium chloride crystals, sodium hydroxide (solid), and 100% ethyl alcohol. In an enclosed space, these substances deplete the water vapor present to a definite degree. Other substances are used to accomplish this end by chemical reaction, e.g.. phosphorus pentoxide (forming phosphoric acid), and boron trioxide (forming boric acid). Water is absorbed from nonmiscible liquids by addition of such substances as anhydrous sodium sulfate, potassium carbonate, anhydrous calcium chloride. and solid sodium hydroxide. The converse phenomenon is known as efflorescence. 

With some substances, not necessarily salt hydrates, the reverse of efflorescence occurs. For example, if anhydrous calcium chloride is left in the air, it absorbs water vapour and eventually forms a very concentrated solution. This process is called deliquescence, and substances which behave like this are said to be deliquescent. Solid sodium hydroxide will deliquesce. 

Sodium carbonate decahydrate effloresces quite readily. With some substances, such as solid sodium hydroxide, the reverse of efflorescence occurs - they deliquesce. There are some substances, such as concentrated sulfuric acid, which when left open to the atmosphere are diluted - they are hygroscopic. 

The sodium carbonate lost weight because it lost its water of hydration through evaporation. The sodium hydroxide gained weight because it absorbed water from the air. How do you think this information could be put to practical use Remember, loss of water is efflorescence and gain of water is deliquescence. 

It is a white, crystalline solid, very deliquescent, freely soluble in water, and moderately soluble in alcohol. When exposed to air it evolves hydrogen sulphide,1 and is completely decomposed by heat into this gas and sodium monosulphide.2 The anhydrous salt is also obtained by the interaction at 300° C. of sodium monosulphide and hydrogen sulphide free from carbon dioxide and oxygen.3 Sabatier s4 method is to saturate a solution of sodium sulphide with hydrogen sulphide, and concentrate in an atmosphere of the same gas. A solution can be obtained by saturating sodium-hydroxide solution with hydrogen sulphide. A dihydrate and a trihydrate have been described.5... 

Sodium phosphites.—Disodium hydrogen phosphite, Na2HP03,5H20, is obtained by concentration of a solution of phosphorous acid neutralized with sodium carbonate, and over sulphuric acid changes to the anhydrous salt. The pentahydrate is very deliquescent. The anhydrous salt melts at 53° C., and above this temperature is oxidized to sodium phosphate, with evolution of phosphine.7 The heat of formation from the elements is 285 1 Cal.,8 and from the acid and sodium hydroxide in solution 28 45 Cal.9 The heat of hydration of the anhydride to the pentahydrate is 18 7 Cal. 

Sodium Tungstocyanide, 2Na4[W(CN)s].5H20, may be obtained by neutralisation of the free acid with sodium hydroxide, or by double decomposition from the silver salt and sodium chloride. It yields small yellow deliquescent crystals. 

Trimethylarsine oxide, (CH8)8AsO, may be obtained either by the action of oxygen on trimethylarsine, or by treating cacodyl oxide in methyl alcohol solution with methyl iodide and sodium hydroxide. It forms deliquescent crystals. When its aqueous solution is saturated... 

Chloromercurithiophene or mercury 2 2 -dithienyl is treated with arsenious chloride and the product warmed on the water-bath. The filtrate from this mixture is treated with aqueous sodium hydroxide, then with hydrogen peroxide. Addition of barium chloride then helps to remove any inorganic arsenic which has not crystallised out as sodium arsenate. The whole is filtered, the filtrate freed from barium and sulphuric acid and evaporated down after the addition of concentrated hydrochloric acid. The residue is dissolved in alcohol, boiled with charcoal, and treated with sodium hydroxide. The sodium salt of the arsinic acid crystallises out in transparent, colourless, non-deliquescent, rhombic plates, which are very soluble in water. The free acid forms tufts of needles, M.pt. 185 5° C., fairly soluble in water or alcohol. At 106° to 108° C. it is converted into the corresponding anhydride. Sulphurous acid in the presence of a trace of hydriodic acid reduces it to thienyl-2-arsenoxide, whilst with sodium hydrosulphite it yields 2 2 -arsenothiophe-ne,... 

Sodium hydroxide occurs as a white or nearly white fused mass. It is available in small pellets, flakes, sticks, and other shapes or forms. It is hard and brittle and shows a crystalline fracture. Sodium hydroxide is very deliquescent and on exposure to air it rapidly absorbs carbon dioxide and water. 

CAS 1313-82-2. (1) Na2S. (2) Na2S 9H20. Properties Yellow or brick-red lumps or flakes or deliquescent crystals. (1)D 1.856 (14C), mp 1180C (2) d 1.427 (16C), decomposes at 920C. Soluble in water slightly soluble in alcohol insoluble in ether largely hydrolyzed to sodium acid sulfide and sodium hydroxide. 

How could you determine quantitatively whether sodium hydroxide or calcium chloride is more deliquescent ... 

Loss of water usually causes a breakdown in the structure of the crystal this is commonly seen with sodium sulfate, whose vapor pressure is sufficiently large that it can exceed the partial pressure of water vapor in the air when the relative humidity is low. What one sees is that the well-formed crystals of the decahydrate undergo deterioration into a powdery form, a phenomenon known as efflorescence. When a solid is able to take up moisture from the air, it is described as hygroscopic. A small number of anhydrous solids that have low vapor pressures not only take up atmospheric moisture on even the driest of days, but will become wet as water molecules are adsorbed onto their surfaces this is most commonly observed with sodium hydroxide and calcium chloride. With these solids, the concentrated solution that results continues to draw in water from the air so that the entire crystal eventually dissolves into a puddle of its own making solids exhibiting this behavior are said to be deliquescent. 

Sodium hydroxide (SO-dee-um hye-DROK-side) is a white deliquescent solid commercially available as sticks, pellets, lumps, chips, or flakes. A deliquescent material is one that absorbs moisture from the air. Sodium hydroxide also reacts readily with carbon dioxide in the air to form sodium carbonate. Sodium hydroxide is the most important commercial caustic. A caustic material is a strongly basic or alkaline material that irritates or corrodes living tissue. The compound ranked number n among chemicals produced in the United States in 2004. 

Diethylisoamylphosphine, C5Hu.P(C3115)2, occurs when tri-ethyH oamylphosphonium chloride is subjected to dry distillation. It is a colourless, slightly viscous liquid, B.pt. 185° to 187° C., which does not oxidise so readily as triethylphosphine, and has an odour resembling that of fusel oil. The liyd)ochloiide formed in the foregoing decomposition boils at 270° to 271° C., is very deliquescent, and with sodium hydroxide yields the free phosphine. 

Na20) A highly reactive whitish deliquescent solid that combines violently with water to form sodium hydroxide. 

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