SUMMARY The determination of the particle size of Intralipid fat emulsions by the nonperturbing method of photon correlation spectroscopy has been extended to include particle size determination using the Coulter counter and optical microscopy. Although little increase in particle size in 3‐litre bags containing total parenteral nutrition mixtures was observed with the methods involving large dilutions, creaming was observed and optical microscopy showed aggregation and some coalescence to have taken place. The problem of re‐dispersion upon dilution of aggregated (but not coalesced) fat emulsions makes direct optical observation essential in assessing the stability and safety of such fat emulsion mixtures. The effect of electrolytes (NaCl and CaCl2) on creaming, particle size and electrophoretic mobility showed both minimum stability and minimum zeta potential at 3 × 10‐3mol dm‐3 CaCl2and at 2. 5 × 10‐1mol dm‐3NaCl. Thus, these maximum levels for electrolytes in total parenteral mixtures are indicated.

The polarography of picolinic acid, isonicotinic acid and their amides has been studied over a range of pH values. In all eases the wave heights decrease rapidly when certain pH values are reached. In contrast to the acids, which show only one type of wave each, the amides have two different types of waves.The dependence of the wave heights on pH is discussed in terms of a recombination reaction taking place in the electrode interface.

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Die bisquaternären Ammoniumsalze (V) und (X) werden, wie im Schema angegeben, synthetisiert.

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