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NITRO DERIVATIVES OF PHENOL 487

setting point 121.3°C Kast [40]). When heated to a temperature above its melting

point it begins to sublime.

Specifications for commercial picric acid differ in various countries but the

setting point should never be lower than 120°C.

Solubilty. Doliriski [41] gave the following figures for the solubility of picric

acid in water at various temperatures (Table 109) (see also Findlay [41a]).

TABLE 109

SOLUBILITY OF PICRIC ACID IN WATER

Temperature

°C

Content of picric acid, g

in 100 g of the

solution

in 100 g of the

solvent

0

10

20

30

40

50

60

0.67

0.80

1.10

1.38

1.75

2.15

2.77

70 3.35

80 4.22

90 5.44

0.68

0.81

1.11

1.40

1.78

2.19

2.81

3.47

4.41

5.72

100 6.75 7.24

The solubility of picric acid in sulphuric acid varies with the concentration

of the latter. It is highest for concentrated acid and lowest in 18-20% acid. This

can be seen from Table 110 [41b].

TABLE 110

SOLUBILITY OF PICRIC ACID IN H 2 SO 4

H 2 SO 4

CONCENTRATION

%

PICRIC ACID CONTENT IN 100 G

OF THE SOLUTION

18°C 50°C 80°C

0 1.184 2.399 4.541

2.3 0.230 0.692 1.940

4.7 0.142 0.368 1.251

10.0 0.091 0.265 0.727

18.0 0.079 0.214 0.561

25.5 0.092 0.230 0.587

50.5 0.429 0.645 1.104

69.7 0.928 1.424 2.203

87.9 2.461 5.826 7.610

97.4 7.531 12.785 24.020

100.0 10.180 16.230 25.860