178 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 61 • NO ADDED ELECTROLYTE 59 •'• --•-- O.00l g/lOOml. K CI 57 -•,, -- -- 0.01 g/lOOrnl. K CI -.- o., //• --o-- 1.0 g/lOOml. K CI C.) •,",•/ • --x-- '0.0 g/lOOm,. K C, . 51 ••x • 49 o_ 47 •b_. 43' TENSION •• •••. 41 - VS. SURFACE rr CONCENTRATION g 3• - E5 PRODUCT $? - 35 I I I • •o.ooo• o.ool o.o• o. • •.o •o.o CONCENTRATION OF ETHOXYLATE (g/ IOOml ) Figure 13. Variation of surface tension as a function of concentration of E5 ethoxylate in the presence of potassium chloride There was, in most cases, fair agreement between the two methods. Emulsion type was determined from electrical conductivity, aqueous dispersibility, and microscopic examination of the completed emulsions. Sudan Red, as previously mentioned, was added to the oil phase of the formulations. Microscopic observations of the experimental formula- tions were used to determine which phase of the emulsion was dye- stained. Emulsion type was then classified on the basis of agreement among the several methods. The measurements of emulsion type were taken 30 minutes after completion of the formulation. To eliminate the possibility of affecting the experimental results through the ethoxylate mineral oil ratio, several variations were studied. The presented formulations have large ethoxylate/mineral oil ratios. Therefore, several emulsions were formulated in which the percentage of mineral oil was kept constant and the amount of ethoxylate was re- duced from 10 to 7%. A second approach to reducing the ratios con- sisted of increasing the mineral oil while the percentage of ethoxylate was held constant at 10%. Emulsions in this series were formulated with 10% mineral oil. The results obtained, where measurements were possible, indicated that ratio variations did not significantly alter the experimental results. Therefore, it was concluded that the electrolyte-

ELECTROLYTES AN[) EMULSION STABILITY 179 emulsifier interactions were similar and affected the emulsion param- eters in the same manner over several ratio variations. Data on particle size, pH, emulsion type, and viscosity were obtained from two series o[ experimental emulsions as follows: A. Each member of this series contained the single ethoxylate. Electrolyte was not included in any emulsions of this series. Formtllations consisted of only three components: 1. El5, El0, or E5 ethoxylate ..................... 10% by wt. 2. Mineral oil (65/75 Saybolt) ..................... 5% by wt. 3. Deionized water ............................... 85% by wt. B. Members of this series contained one single ethoxylate. How- ever, electrolyte was included in varying concentration in all formulations: 1. El5, El0, or E5 ethoxylate .................. 10% by wt. 2. Mineral oil (65/75 Saybolt) .................. 5% by wt. 3. Calcium, potassium, or sodium chloride ........ 0.001%, 0.01%, or 10.0% by wt. 4. Deionized water .............................. q.s 100% DISCUSSION O•' EXPERIMENTAL RESULTS Microscopic observations of the internal phase indicated a variation in mean particle diameter which was influenced by the choice of the ethoxylate and the nature and quantity of electrolyte (Tables I-liD. In emulsions which contained the ethoxylate in the absence of added electrolyte, the E5 product formed particles of smaller mean diameter than did the El5 or El0 ethoxylates. The significance of this observa- tion was pointed out in an earlier publication (6). Experimental emul- sions which contained the ES, El0, and El5 ethoxylates together with increasing concentrations of potassium, sodium, and calcium chlorides exhibited distinct variations in particle size. With increasing concentra- tions of sodium, potassium, or calcium chlorides the mean diameter of the particle decreased. A direct relationship was observed between diminishing particle size and increasing electrolyte concentration up to 10%. Further studies were undertaken at a later date in which the electrolyte content was increased to 29%. In the case of the El0 and El5 products, there was further reduction in the mean emulsion particle diameters. In the case of the E5 formulations, 2I)% of sodium, potas- sium, or calcium chloride increased the particle size.