VITAMIN C AND SDS/PENTANOL/WATER SYSTEM 0.004 -----......------.......----- 55 0.0035 0.003 l 0.0025 b 0.002 "iii � 0.0015 0.001 0.0005 . - - - , - - - - -,- - - - - r - - - - r - - - - �iscoslty [Pax s] �shear rate (1/s] 50 45 ,!! 40 ;' 35 i 30 25 Cl) .c Cl) 0+-----.---.-----.,---....----.�-... 20 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 Shear Stress (Pa) 0.045 --------------------- 55 0.043 0.041 _ 0.039 = 0.037 e:. b 0.035 .§ 0.033 0.031 0.029 0.027 - - - - - , - - - - - � - - 50 45 40 � .! &! 35 i 30 25 Cl) .c Cl) 0.025 .... --.---.--.....--.... --...---+ 20 1.1 1.2 1.3 1.4 1.5 1.6 Shear Stress (Pa) 0.01 ----------------.------ 55 0.0095 - - - - - • - - - - - _, - - - 0.009 e 0.0085 ca i 0.008 'jg � 0.0075 0.007 0.0065 �cosily [Pax s] 50 45 ,!!! 40 � .! &! 35 1 30 .c Cl) � rate [1/s] 25 -- - - 1 - - - - - - , - - - - - - I - - - - - 0.006 +---.--....�--.--....--..---+ 20 0.15 0.2 0.25 0.3 0.35 0.4 0.45 Shear Stress (Pa) 271 Figure 3. Flow curves for (a) W /0 microemulsion, (b) biconrinuous system, and (c) O/W microemulsion.

272 JOURNAL OF COSMETIC SCIENCE 0.03 ----------.,.......--....---------------------.. 0.025 0.02 'iii )I( Ill a. i 0.015 .§ 0.01 0.005 a) 15°C - - - - - - -;- - - - - - - I - - ' ' • 1 - - - - - - - - - ---- - - - - - ... - - - - - -- - - I I I I --+--no vii. C ' '\. --2%vit.C • • • 10%vit.C c ______ 0 __ .'1!1!9� ______ C _______ , _______ , _ •• '- ' --e • 20%vit.C : .. • : -1: • 60%vit.C : ..._:..,. • - - - - - - � - - - - - - + - - - ' ' 0..--------------------------------...... )I( Ill a. 0 10 20 30 40 50 60 70 80 90 100 Water Content in Microemulsion (Wt%) 0.03 --------.---.,.......--....-----------.....-----.-----.-----, 0.025 0.02 I I I I I I - - - - - - I - - - - - - I - - - - - - T - - - - - - I - - - - - - 7 - - - - - - I - - - - - I ! I I ___ �1 ii�c- _ � _____ - l - _____ J _ - - - - _ J _ � -�- �- - - - - - ) _ - - - - - -:- - - - - - ) _ - - - - - - ,, --+--novlt. C .. i 0.015 --a -2% vit. C .. -& .. 10%vit.C --e • 20%vlt. C WI_� i - - - - - - " - - - - - _, - - - - - � _ - - - ' ! ' "\. .8 0.01 0.005 0..---------------------------------.. 0 10 20 30 40 50 60 70 80 90 100 Water Content in Microemulsion (Wt%) Figure 4. Influence of ascorbic acid concentration on the viscosity of the microemulsion region of the SDS/penranol/water system: (a) temperature l 5 ° C, (b) temperature 22°C, (c) temperature 30°C, and (d) temperature 40°C. The microemulsion was prepared by titration of penranol and sodium dodecyl sulphate mixtures of various weight ratios by ascorbic acid water solution. This mixture was vigorously mixed to obtain a clear and highly stable microemulsion. To determine the influence of ascorbic acid on the rheology of SDS/pentanol/H 2 O microemulsions, samples with 6% SDS (percentage by weight) and increasing contents of ascorbic acid were examined (along a dashed line corresponding to 6% SDS in the phase diagram) (Figure 1 (18,37) Table I).