USE OF TERNARY DIAGRAMS 469 ADVANTAGES Or THE SYSTEM The major advantage of combining ternary diagrams with the concept of crossed and paralleled series is to reduce the number of samples required to obtain desired information. Let us illustrate the use of this concept with ternary diagrams to solve a typical problem: finding the most stable W/O emulsion using a particular emulsifier. Such a system may be represented by a ternary diagram as in Fig. 8. Ten samples along a line from "B" to the vertex representing "100 per cent 60% 50•.P 0% •0• Cleo, t' Liclu d C l o-dy Cle• Hazy Opaque 10% ..,qoa. p- Oil 10% 50• Alcohol C larit 7 at 25 ø C Oro nao'hol •-0 % Water c)0%W•ter Fig. 10 water" were first prepared and tested. The most stable one was found at point "C." Using the principle of crossed series, a line from "100 per cent Emulsifier" through point "C" to point "E" was drawn, and a series of ten samples again prepared, more closely spaced, however, and all in the region of points "C" and "E" because the least possible emulsifier was desired. An improvement over "C" was found at point "D." Another improvement was found at point "F" on a line drawn from the "oil vertex" through point "D." The area was now small enough for the use of a small group of paralleled series samples closely spaced around "F." Of these, several for-

47O JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 60 ø/,, ,5 oap-Oil 0% Alcoho• XkO% Vdaq'e r Cl•ar Ljquid Clear HQzy 10% O,l-$o.p Clarity at •0% Alcohol O%Alcohol 40% Water 90% Water Fig. 10A mulas (quite closely spaced) were found to be best for stability. Fur- thermore, they were definitely the best possible for the system, not just the most satisfactory produced so far. The problem just demonstrated has been oversimplified to illustrate more clearly the procedure of employing the ternary diagram as a tool in formulation work. In practice, more than three variables will be en- countered. Therefore, to demonstrate the value of the method in greater detail we have applied it to a practical, but much more complex problem. A C•,EAR GE•, A solid clear gel with emollient properties was desired one as inexpensive as possible. Emollient products often contain oily materials incompatible with water, yet water is desirable for reasons of economy. The literature showed that certain proportions of soap and alcohol form clear gels with water and oil. Certain alkali metal soaps were noted as being most effi- cient for this purpose. However, these clear gels were quite susceptible to changes in temperature, a factor which had to be considered as the formula evolved.