Sodium nitrate deliquescence

A. Speransky, the vap. press, p of a sat. soln. of sodium nitrate at T° K. can be represented by Bertrand s formula log p=7 5172+50 log [(T—74 8)/T], The mol. wt. calculated from the lowering of the vap. press, corresponds with a very large percentage ionization, and the decrease which occurs with an increasing cone, shows that there is a disturbing facto —hydration. Similar remarks apply to the results with potassium nitrate soln. G. Tammann has studied the lowering of the vap. press, of water, at 100°, by soln. of the alkali nitrates. E. B. R. Prideaux studied the vap. press, of soln. of sodium and potassium nitrates, and studied the deliquescence and drying of these salts. 

Anhydrous lithium nitrate is very deliquescent and sodium nitrate is also deliquescent. Since the last-named salt becomes damp on exposure to the air it cannot be used for some purposes for which potassium nitrate is applicable. Potassium, rubidium, and caesium nitrates do not deliquesce under the same conditions, although G. J. Mulder43 showed that if potassium nitrate be confined under a bell-jar over water at 14° to 20°, it does deliquesce and E. L. Kortright found the same salt at 20° to deliquesce when the partial press, of the water vapour exceeds 15 5-16 5 mm., and sodium nitrate when the partial press, of the water vapour exceeds 123-135 mm. A salt can be deliquescent only when the press, of the water vapour from its sat. soln. exceeds the partial press, of the water vapour in the surrounding air. If pi be the vap. press, of water, p, the vap. press, of a sat. soln. of the salt containing S grms. of salt pet 100 grms. of water, and k be the constant of proportion to be evaluated from the observed data, R. Emden has shown that Sk=(p—pi)/p, which enables p% to be computed from the values of p and S. The deliquescence press, of the water vapour for sodium nitrate at 0°, 10°, 20°, and 30° is then 3 5, 6 9, 12 8, and 22 6 mm. respectively, and for potassium nitrate, 4 4, 8 7, 16 0, and 28 3 mm. respectively. 

Sodium nitrate is a very deliquescent substance,15 and is therefore unsuited for the manufacture of explosives. It is employed in agriculture as a fertilizer, and by double decomposition with potassium chloride yields potassium nitrate. Large quantities are reduced to... 

Deliquescence is a property of substances very soluble in water. When such substances, potassium carbonate or calcium chloride for example, are exposed to the air, the water vapor forms with the substance a small quantity of a saturated solution. This saturated solution has a lower vapor pressure than that of the atmosphere, that is, the water is held by the substance, it does not tend to escape, hence more water vapor is added from the air, and finally the substance is entirely dissolved in this condensed vapor. Common salt or sodium chloride often appears to deliquesce, but the deliquescence is due to the very soluble magnesium and calcium chlorides which are usually mixed with commercial sodium chloride. Sodium nitrate is very soluble in water at the ordinary temperature, but potassium nitrate is only slightly soluble. Hence potassium nitrate, and not sodium nitrate, is used in the manufacture of gunpowder. 

Figure 12.5 The hygroscopic and deliquescent nature of sodium nitrate crystals observed under the scanning electron microscope in the laboratory. The scale bar is 100 pm.

The hygroscopic and deliquescent properties of sodium nitrate also mean that nitrate speleothems, of which there are some examples, are transient features that come and go with the seasons (Hill and Forti, 1997). The threshold temperature for the transition from deliquescence to crystallisation takes place at 42°C (Pantony, 1961). The critical relative humidity (RH) at which the liquid phase starts to appear on crystals of sodium nitrate is 73.8% at 25°C for pure sodium nitrate, but impurities such as sodium... 

Sodium Nitrate—Cubic or Chili saltpetre—-Sodii nitras (TJ. S.) —Sodee nitras (Br.)—NaNO,—85—occurs in natural deposits in Chili and Peru. It crystallizes in anhydrous, deliquescent rhom-bohedra cooling and somewhat bitter in taste fuses at 310° (590° F.) very soluble in HaO. Heated with HaSOi, it is decomposed, yielding HNOa and hydrosodic sulfate HaS04- -NaNOa —HNaS04+HNOa. This reaction is that used for obtaining h no3. 

Chile saltpeter is composed of sodium nitrate, NaNOj. It is found in South America, particularly in Chile. It occurs in beds that vary in thickness from 15 cm to 3.6 m. These beds, called caHche, are interspersed with deposits of gypsum, sodium chloride and other salts, and sand. The caliche is quarried and purified in Chile before the product is ejcported. It is used extensively as a fertiHzer but not in the manufacture of gunpowder because of its deliquescence. 

If made for immediate use the sodium nitrate salt can be used with advantage—this salt giving a deeper tint It is, however, unfortunately most deliquescent (liable to absorb moisture), and must be most carefully dried in an... 

Sodium Nitrate n (1885) NaN03. A deliquescent crystalline salt used as an oxidizing agent, a fertilizer, and in curing meat. 

Atmospheric aerosols are hygroscopic, taking up and releasing water as the RH changes (see also Section C.l) because some of the chemical components are themselves deliquescent in pure form. For example, sodium chloride, the major component of sea salt, deliquesces at 298 K at an RH of 75%, whereas ammonium sulfate, (NH4)2S04, and ammonium nitrate, NH4N03, deliquesce at 80 and 62% RH, respectively. (See Table 9.16 for the deliquescence points of some common constituents of atmospheric particles.) De-... 

The other alkali metal nitrates yield the nitrites and oxygen. Only the lithium and sodium salts are deliquescent. 

Citric acid (Kahlbaum), CsHsOy H2O. Molecular weight 210.0. Commercial samples may be recrystallized twice from water and then dried to constant weight over deliquescent sodium bromide. The acid contains one molecule of water of crystallization. Sorensen specifies that solutions of the acid should be clear and give no reaction with barium and silver nitrates. The ash content of 5 g, should be less than 1 mg. Drying at 70° and 20-30 mm. pressure removes the water of crystallization, which corresponds to an 8.58% db 0.1% loss in weight. 

Characters and Tests.—Hard and greyish-white, very alkaline and corrosive. Does not deliquesce on exposure to the atmosphere. It imparts a yellow colour to flame, indicating the presence of sodium, and its solution in water, acidulated by nitric acid, should give only scanty white precipitates with argentum nitrate and barium chloride, showing the presence of traces only of chlorides and sulphates respectively. 

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