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OTHER NITRO DERIVATIVES OF PHENOLS 529

TABLE 121

DETONATION RATE OF AMMONIUM PICRATE (BOTH FORMS)

AT VARIOUS DENSITIES (IN A STEEL PIPE 35/42 mm)

1.56

1.58

1.60

Density, g/cm^3

0.86

1.11

1.34

1.35

1.49

1.50

1.55

Detonation rate, m/sec

yellow form red form

4380 -

• 5155
  5835 -
  5835
  6950 -


• 6960
  6995 -
  -. 6995
  6200
  6030 -

As the highest rate of detonation under the above condition, 7000 m/sec for

both forms has been taken. Thus, ammonium picrate should be considered as

a somewhat more powerful explosive than TNT.

The thermochemical properties of ammonium picrate have been examined

by several authors (no indication given as to the colour of the substance examined).

Sarrau and Vieille [17] determined its heat of combustion as ranging from 693.2

to 708.9 kcal/mole.

T. Urbanski and Soroka [18] determined heats of combustion of the two

forms and from these they calculated their heats of formation:

Heat of combustion (−∆ HR) Heat of formation (−∆ Hf)

yellow form 687.3 kcal/mole 83.7 kcal/mole

red form 677.3 kcal/mole 93.7 kcal/mole

It can be seen that the calculated heat of explosion of the red form is somewhat

lower than that of the yellow one.

These results do not agree with Hale’s data. He reported the fragmentation

of 3 in. shells might indicate the higher explosive power of red ammonium picrate,

and the equal abilities of the two forms to detonate under the influence of a deto-

nator.

Ammonium picrate under the name of Explosive D was first used in the United

States in 1901. It was Dunn [18a] who proposed using it as a high explosive material

for filling shells. During both the World Wars armour piercing shells of the U. S. Navy

were filled with this explosive. It is thought that ammonium picrate is less sensitive

to impact and friction than TNT, and that is why it was used for the purpose. However,

the above mentioned investigations by T. Urbanski and his co-workers did not

confirm the view. Moreover, they revealed that ammonium picrate, and especially

its yellow form, was easy to ignite when in contact with a flame, its flammability

being of the same order as that of gunpowder.