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HEXAMETH TLEXETETRAMIXE 2s; •>o
Impure hexamethylenetetramine may be purified by recrystallization
from solvents .such as alcohol and chloroform, orb}'precipitation from aqueous
solution by saturation with ammonia gas. According to Ohara*\ material
of the highest purity is obtained by the latter procedure.
Aqueous solutions of hexamethylenetetramine are mildly basic, having
pH values in the neighborhood of S to 8.5 for concentrations ranging front
approximately 5 to 40 per cent, Russo w reports its dissociation constant
as 1.4 X 10~ & .
Pure water solutions of hexamethylenetetraniine are comparatively stable
at ordinary temperatures, showing only an extremely slight degree of
hydrolysis to formaldehyde and ammonia. According to Fincke 44 , the
formaldehyde content of a pure solution, after standing 15 hours at room
temperature, is approximately 5 parts per million. Hydrolysis may be
Table 2d. Solubility of Hexamethylenetetramine* in Various Solvents 1 ' 3 .
Solvent
Petroleum ether
Ethyl ether
Trichlorethylene
Xylene
Carbon bisulfide
Benzene
Tetrachlorethane
Acetone
Carbon tetrachloride
Amyl alcohol
Absolute ethanoi
Methanol
Chloroform
* Data of Utz m .
Solubility In g Hexamethylenetetramine
per 100 cc Solvent
Room Temp. Elevated Temp.
Insoluble
0.06
0.11
0.14
0.17
0.23
0.50
0.65
0.S5
1.S4
2,89
7.25
13.40
Insolub
0.3$
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~—
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11.93
14. S4
appreciably reduced by the addition of small amounts (0.1 to 1 per cent) of
sodium carbonate 98 and is accelerated by the addition of acid. According
to Philippi and Lobering 81 , the hydrolysis constant is a function of pH, decreasing
from about 2 X I0~ s at pH values in the neighborhood of 2 to 1 X
10~ 4 at pH €. Hydrolysis is also accelerated by heating. In a study of
the effect of steam sterilization on ampoules of 25 per cent hexamethylenetetramine
solution prepared for medicinal use, Toni 109 reports that a freshly
prepared, formaldehyde-free solution whose pH was 8.32 showed a formaldehyde
content of 0.07 per cent and a pH of 9.50 after 3 months' storage.
whereas a solution which had been steam-treated showed a formaldehyde
content of 0.12 per cent and a pH value of 10,01. The rise in pH is an
index of ammonia liberation. Vickers 11 * observed that ammonia and
formaldehyde tend to recombine on standing at room temperature after
heating in sealed containers.