Deliquescent, definition

It is a white, deliquescent solid, very powdery, which exhibits polymorphism on heating, several different crystalline forms appear over definite ranges of temperature -ultimately, the P4O10 unit in the crystal disappears and a polymerised glass is obtained, which melts to a clear liquid. 

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. 

The product is hydrated rhodium trichloride, which, according to Claus 6 contains eight molecules of water. Leidie,1 on the other hand, concluded that the amount of water varies and does not correspond to any definite hydrate. It is an amorphous, briek-red, deliquescent substance which, on heating to 90-95° C., still retains four to five molecules of water and two of hydrogen chloride. At 100° C. it loses water and hydrogen chloride simultaneously, and at 175-180° C. it is completely dehydrated. At 360° C. it becomes insoluble in water, hut it is most... 

The salt separates out in hydrated crystals, which are usually pale violet in colour, the extent of hydration varying according to circumstances. Two definite hydrates are known6 namely, the nonahydrate,6 Fe(N03)3.9H20, which yields pale red deliquescent monoclinic crystals,7 of the following crystallographic elements —... 

Standard solution A solution that contains a known weight of the reagent in a definite volume of solution. A standard flask or volumetric flask is used for this purpose. The solutions may be prepared by direct weighing for primary standards. If the reagent is not available in a pure form or is deliquescent the solution must be standardized by titration against another known standard solution. 

We begin with the definition of deliquesce. The Oxford English Dictionary traces the verb to the Latin de- + liquescere to melt away, dissolve, disappear [86]. We can imagine a grain of salt in a humid environment being transformed into a brine droplet. The thermodynamic condition for this phase transition is most simply obtained by measurement of temperature and vapor pressure of a saturated salt solution. At 25 °C this is 24 mbar [78]. With the vapor pressure of neat water at this temperature of 32 mbar [77], the deliquescence of NaCl corresponds to 75% RH. 

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