Solubility of Nitrogen

There are three ways of expressing the relationship of solubility by volume between gases and liquids.

1. Absorption coefficient β (Bunsen) is the volume of gas, reduced to N.T.P., which is absorbed by unit volume of liquid, when the pressure of the gas is 760 mm. without the vapour tension of the liquid.
2. Solubility β' is the volume of gas, reduced to N.T.P., which is absorbed by unit volume of liquid, when the total pressure is 760 mm. (i.e. including the vapour tension of the liquid),
   
   β' = β(760-f)/760,
   where f=vapour tension of liquid at the temperature of the experiment.
3. Solubility coefficient l (Ostwald) is the volume of gas dissolved by unit volume of liquid at the temperature and pressure of the experiment. It is not reduced to N.T.P. Hence, if the measurements are made at atmospheric pressure,
   
   l=β(1+0.00367t).

The following table gives the solubility of nitrogen in water in terms of the absorption coefficient β:

Solubility of nitrogen in water

Temp.° C.	Atmospheric Nitrogen.		Argon-free Nitrogen.
	Winkler	Fox	Winkler	Fox
0	0.02354	0.02359	0.02312	0.02319
10	0.01861	0.01895	0.01829	0.01863
20	0.01545	0.01598	0.01518	0.01572
30	0.01342	0.01398	0.01319	0.01375
40	0.01184	0.01252	0.01164	0.01233
50	0.01088	0.01133	0.01071	0.01160

The formula deduced by Fox for the solubility of pure nitrogen is

1000β=22.998-0.5298t+0.009196t²-0.00006779t³,

which is obtained by allowing for 1.185 per cent, argon.

The Rate of Solution of Nitrogen in Water. - Adeney and his collaborators have investigated the rates of absorption of nitrogen, oxygen, and air by water under gentle agitation. The results are summarised by the formula


where
w=initial percentage saturation capacity for nitrogen.
w₁=amount dissolved after a given time θ.
e=Napierian logarithmic base.
F=0.0103 (T - 240).
A=area of water exposed to the gas.
V=volume of water.

As in the case of oxygen, the solubility of nitrogen in sea-water decreases with increasing chlorine content. The calculated formula expressing these results is:

1000β=18.639-0.4304t+0.007453t²-0.0000549t²-Cl(0.2172-0.007187t+00000952t²),
the chlorine being expressed as grams per litre.

Solubility of nitrogen containing argon in sea-water from a free, dry atmosphere at 760 mm

Parts of Chlorine per 1000.	Temperature, ° C.
	0	4	8	12	16	20
0	18.64	17.02	15.63	14.45	13.45	12.59
4	17.74	16.27	14.98	13.88	12.94	12.15
8	16.90	15.51	14.32	13.30	12.44	11.70
12	16.03	14.75	13.66	12.72	11.93	11.25
16	15.18	14.00	13.00	12.15	11.73	10.81
20	14.31	13.27	12.34	11.57	10.92	10.36

The solubility of nitrogen in aqueous solutions of barium and sodium chlorides is as follows:

Solubility of nitrogen in aqueous salt solutions

Temperature, °C.	Coefficient of Absorption in Barium Chloride Solutions.
	13.83 per cent.	11.92 per cent.	6.9 per cent.	3.87 per cent.	3.33 per cent.
5	0.0127	0.0137		0.0160	0.0180	0.0183
10	0.0117	0.0125	0.0147	0.0166	0.0168
15	0.0104	0.0114	0.0132	0.0148	0.0150
20	0.0092	0.0098	0.0118	0.0132	0.0135
25	0.0078	0.0086	0.0104	0.0114	0.0119
	Coefficient of Absorption in Sodium Chloride Solutions.
	11.73 per cent.	8.14 per cent.	6.4 per cent.	2.12 per cent.	0.67 per cent.
5	0.0102	0.0127	0.0138	0.0179	0.0200
10	0.0093	0.0113	0.0126	0.0164	0.0185
15	0.0081	0.0101	0.0113	0.0147	0.0164
20	0.0066	0.0087	0.0098	0.0131	0.0148
25	0.0047	0.0075	0.0083	0.0113	0.0130

The following table gives the solubility of nitrogen in ethyl alcohol at various temperatures:

Solubility of nitrogen in alcohol

Temperature, ° C.	0	5	10	15	20	24
Absorption coefficient	0.1263	0.1244	0.1228	0.1214	0.1204	0.1198

The solubility of nitrogen in mixtures of ethyl alcohol and water is given by Just.

Solubility of nitrogen in aqueous ethyl alcohol

Per cent. Alcohol.	0	20	33	99.8
Solubility product l25	0.01634	0.01536	0.01719	0.1432

Critical temperature: from -146 to -144.7
Critical pressure: from 32 to 35
Critical density: from 0.31096 to 0.32690

The solubility of nitrogen in natural petroleum is of the same order as that in alcohol; the absorption coefficient at 10° C. is 0.135 and at 20° C. is 0.117.

Nitrogen is much less soluble in aqueous solutions of glycerol and in aqueous solutions of sugars than in water.