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22 CHEMISTRY AND TECHNOLOGY OF EXPLOSIVES

which takes place together with the ordinary ionization:

HNO 3 + H 2 O <-> H 3 O+ + NO 3 - (35)

Increase in concentration involves the formation of N 2 O 5 , consequently the

concentration of NO 2 + ions decreases the equilibrium of the reaction

NO 3 - + NO 2 + <-> N 2 O 5 (24)

being shifted to the right (compare the reaction on p. 19).

The maximum absorption band at 5% water corresponds to the shifting of

the equilibrium to the left, when more NO 2

+

is formed.

In view of the practical application of solutions of ammonium nitrate in nitric

acid in the Koffler-Bachman process for the manufacture of Cyclonite (Vol. III.)

FIG. 8. Ultra-violet absorption spectra of nitric acid-ammonium

nitrate solutions (R. N. Jones and Thorn [58a]).

the investigations of these solutions by R. N. Jones and Thorn [58a] are important.

They examined solutions containing up to 54 g of ammonium nitrate in 100 g of

solution. The results are recorded in Fig. 8. Small additions of ammonium nitrate

cause a decrease in the intensity of the absorption maximum near 262.5 mμ. Fur-

ther addition of ammonium nitrate then causes the intensity of absorption to in-

crease, and it falls again at a higher concentration. The considerable bathochromic
shift of the absorption maximum in a mixture containing 54% of NH 4 NO 3 is

probably caused partly by the additive effect of the nitrate ion absorption maximum
at 301.5 mμ contributed by the ion NO 3 - of the added salt.

Raman spectrum. Extensive Raman spectrum studies have played a special

role in the elucidation of the structure of nitric acid. They have thrown a good