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The ability of methyl‐, methylethyl‐, and sodium carboxymethyl‐cellulose to promote emulsions with liquid paraffin and arachis oil is largely independent of the viscosity of their mucilages. Methyl‐ and methylethyl‐cellulose are more efficient emulsifying agents than is sodium carboxymethylcellulose. Emulsifying efficiency increases with the concentration of the derivative, and low viscosity grades are more efficient than high viscosity grades. Mixtures of these derivatives have little advantage as emulsifying agents over methyl‐ and methylethyl‐cellulose used singly.

A study has been made of the effects of heat, acid and alkali, salts and alcohol on the stability of methyl‐, methylethyl‐ and sodium carboxymethyl‐cellulose emulsions of liquid paraffin. All were stable for 4 to 8 weeks at 40°, but at 80° deteriorated rapidly, the order of decreasing stability being methyl‐, methylethyl‐ and sodium carboxy‐methylcellulose emulsions. Heating at 115° for 30 minutes decreased the stability of sodium carboxymethylcellulose, but not of methyl‐ and methylethyl‐cellulose emulsions. Stability in the presence of added substances depended largely on the physical properties of the reaction products. The results are related to the behaviour under similar conditions of aqueous dispersions of the three derivatives, and the influence on emulsion stability of dehydration and degradation of the emulsifying agent is discussed.

Introduction. Single crystals of C I4H21NO3 formed as clear tablets from a dichloromethane solution upon standing at room temperature. The specimen crystal used to collect the intensity data was of dimensions 0-3 × 0.1 x 0. l mm. Intensity data were collected using a Syntex P2~ automated four-circle diffractometer and graphite-monochromatized Mo Ka radiation, 2 = 0.71069 A. The data crystal was kept at 238 K with a Syntex LT-1 low-temperature inert-gas flow system (N2). Intensity data were measured by the oJ-scan technique, with eg-scan rate variable from 1.5 to 5.0 ° min-l. Each reflection was scanned symmetrically over 1.0 ° in co about the KK maximum and background offset + 1.0 ° in m from the K?t maximum. Four check reflections were remeasured after every 96 reflections. An analysis of check reflections (Henslee & Davis, 1975) indicated no significant change from the initial intensities during the 22.5 h data-collection period. Usual corrections and standard-deviation assignments to the data were as detailed elsewhere (Riley & Davis, 1975); absorption corrections (~ = 0.088 mm -~) were not applied; the p factor was set at 0.05. Of 925 reflections measured in the range 4 ° 5 20 _< 45 °, only 795 with I o > 1.5a (I o) were used in the ensuing solution and refinement of the structure.