30 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS per cent of some dissolved substance. The answer is that the method is not sensitive in that sense--minimum amounts of 5% for recognition being typical also it is a tool for studying the solid portion of a system, not the liquid. POLYMORPHISM OF SIMPLE SATURATED TRIGLYCERIDES The polymorphism of glycerides has been recently and variously re- viewed (5, 6, 7). The views of Bailey and Lutton are in essential agree- ment but differ from those of Malkin. Triglyceride is, of course, the principal type of compound in fats. The single fatty acid triglycerides of which tristearin is typical have three crystalline forms or phases--alpha, beta prime, and beta in increasing order of stability, density, and melting point (see Table 1). T.•BLE 1--Cm•v,•CTER•STmS Or TmsT•.• POLYMO•V•S (6) Short Spacing Form Basis for Nomenclature fk. M.P.,ø C. L.S., •. Alpha 4.15 line 54 50.6 Beta prime 4.2 and 3.8 lines 64 46.8 Beta 4.6 line 73.1 45.15 The characteristic appearances of the diffraction patterns of tristearin are shown in the drawings of Fig. $. The so-called short spacings which give rise to the outer group of rings are related to the planar distances of separation of the rows of long parallel hydrocarbon chains which are a major portion of glyceride molecules the long spacings which give rise to the inner rings are related to lengths (or integral multiples of the lengths) of the long molecules. The alpha crystalline form is obtained by chilling the melt, beta by crystallization from solvent or transformation of the metastable forms at elevated temperatures. The somewhat elusive beta prime can best be ob- Alpha Beta Prime Beta Figure 5.--Main features of tristearin diffraction patterns.