Lithium nitrate, LiNO₃

Evaporation of an aqueous solution of nitric acid neutralized by lithium carbonate yields at ordinary temperatures deliquescent needles of the trihydrate, LiNO₃,3H₂O; at 30° C. the semihydrate, 2LiNO₃,H₂O; and at 90° C. the very deliquescent anhydrous salt, LiNO₃, melting-point 253° C., D₄=2.366. Lithium nitrate is very soluble in water, readily yielding supersaturated solutions. At 19.05° C. 100 grams of saturated solution contain 40.4 grams, and at 70.9° C. 66.1 grams. Donnan and Burt have plotted a solubility-curve, which indicates the transition-temperature of the trihydrate into the semihydrate to be about 29.9° C. (C), and that of the semihydrate into the anhydrous salt to be about 61° C.(D). The boiling-point of a saturated aqueous solution in contact with the solid is above 200° C.

Solubility curve of lithium nitrate (LiNO3).

References to other investigations of the properties of dilute solutions of the nitrate are appended.

The heat of formation of lithium nitrate in dilute solution is given by the equation

[Li] + (N)+3(O) +Aq. =LiNO₃, Aq. + 116.1 Cal.

Its heat of solution is only 0.3 Cal., a phenomenon probably due to the formation of hydrates. It follows that the heat of formation of the anhydrous salt from its elements is given by

[Li]+(N)+3(O)=[LiNO₃] + 115.8 Cal.

The heat of solution in alcohol is 4.66 Cal.

With ammonia in absence of water lithium nitrate forms a liquid characterized by its lack of action on machine-steel, iron-wire, or nichrome-wire after contact for several months. It has been suggested that the addition of a small percentage of water would render the liquid a good absorbent for the removal of ammonia from mixtures of the gas with nitrogen and with hydrogen.

The molecular electric conductivity of lithium nitrate between 272° and 440.6° C. is given by the formula

μ_t = 41.14 – 0.238(t – 300).

Lithium nitrate resembles the chloride in the non-formation of isomorphous mixed crystals with the corresponding sodium salt.