Relative Humectant Values

Table 7.10 Relative Humectant Values of Aqueous Solutions of Ethylene Glycol (17)...

Table 7.27 Relative Humectant Values of Propylene Glycol, N.F. (23)...

Table I shows that a 3x3.5 cm dorsal skin wound on a Wistar rat can ooze out 2.2 ml of serous fluid in about 3 days. This fluid volume is reduced to 1.2 ml, if the wound is exposed for 3 hr before treatment. Beyond the 3 hr exposure, there may be further reduction in oozing, but the chance of eschar formation will also increase. Various compositions of the AgN03 medicated dextran hydrogel paste have been evaluated. The one with a good spreadability and fluid absorption has been used in the present study. Measurements by a simple hygrometric method showed that the medicated paste on the wound reduced evaporative loss by almost 50% as compared to an open wound which had a rate of 93 mg H20/cm /hr (7.). On subsequent days, the relatively steady value of 12.5 mg H20/cm /hr was about 2x higher than the evaporative loss of the paste spread over a plastic sheet used as a control. The higher evaporative rate of the paste on the wound site might be due to the transmission of excess moisture from the wound surface. The oozing serous fluid had apparently been first absorbed into the paste, because no exudate accumulation was ever observed under the paste coating. The humectant in the paste which retained moisture obviously must have kept the wound surface sufficiently moist to prevent eschar formation.

A hygroscopic material absorbs moisture from its surrounding atmosphere, while a humectant material is one that resists changes in relative moisture content. The gain or loss of moisture in a com syrup is dependent on the relative humidity of the atmosphere surrounding the syrup. Moisture absorption values for several sweeteners are shown in Table 21.16.79... 

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