It is often observed that the number of catalytic impurities depends on
temperature according to
logNcat&ABT ð 14 : 13 Þwithin a limited temperature range;AandBare constants. This relation can
be interpreted asNcatbeing about proportional to the supersaturation lnb.
Some experimental results are in Figure 14.6, which also shows results on
the initial heterogeneous nucleation rateJ 0 in the same system. (Jhettends to
decrease with time in an emulsified material; see Section 14.3.) The nature of
the catalytic impurities can vary widely and depends on the composition of
the system and on its purity. No general rules can be given. It should further
FIGURE 14.6 Nucleation of emulsified milk fat as a function of cooling
temperature. (a) Concentration of catalytic impuritiesNcat. (b) Initial heterogeneous
nucleation rateJ 0 ; the broken line gives a rough estimate of the homogeneous
nucleation rate. (After results by P. Walstra, E. C. H. van Beresteyn. Neth. Milk
Dairy J. 29 (1975) 35.)