FIXED AND BULK EMULSION WATER 53 50- 40 e30 t0 t I I t I I I I I 20 30 40 50 60 70 80 90 Total water amount [%] Figure 7. The amount of interlamellarly fixed water in water-containing hydrophilic ointment DAB 8 depending on the total water content of the system (O = unstable systems). Glycerol, 85% 10 parts White petrolatum 17.5 parts Water 50 parts These O/W creams also have the typical hydrophilic gel phase. The swelling behaviour of the hydrophilic gel phase is being extensively investigated by De Vringer (6,7). The results of thermogravimetry are represented in Figure 8. All creams investigated show a constant ratio of interlamellarly fixed water and bulk water: only one third of the total water amount exists in the unbound state two thirds are interlamellarly fixed in the hydrophilic gel phase. This ratio is also maintained at very high water contents as well as after phase separation of the system. As an explanation it may be assumed that the separated mixed crystals of (poly)oxyethylated glycerolmonostearate and cetostearyl alcohol keep their very high binding capacity for water molecules also in the liquid emulsion state. A significantly different situation exists with stearate creams, which were produced following a formula given by Tronnier (13): Stearic acid 12 parts

70' 60 • •0 [] , I I I I I I t 10 20 •0 •0 50 60 70 BO To,a• wafer amoun, •-- [ø/o] Figure 8. Ratio of bulk water (e) and interlamellarly fixed water (I) of water-containing non-ionic hydrophilic ointment DAC depending on the total water contents of the systems (o, O = unstable systems). 50- [%1 30- 20- 10' 10 20 30 /+0 50 60 Tofalwaferamounf • [%] Figure 9. Ratio of bulk water (e) and interlamellarly fixed water (I) of stearate creams depending on the total water contents of the systems (O, [] = unstable systems).