PENETRATION OF LANOLIN 227 burette into a 50-ml graduated cylinder and made up to 13.5 ml (if necessary) with chloroform, then up to a total of 25.0 ml with acetic anhydride. To avoid buretting volumes less than i ml, the standard solution when appropriate was diluted 10-fold volumetrically with chloroform to a concentration of 0.037 gl-•. To each prepared mixture of standard lanolin solution and acetic anhydride was added 0.5 ml of concen- trated sulphuric acid by pipette, and the mixture was shaken and transferred to an optical cell. A blank was prepared similarly but using chloroform only, without lanolin, and used for comparison, the absorbance being measured at 458 nm and 25øC at frequent intervals. Absorbance reached a maximum after about 15 to 20 minutes, then began slowly to fall. The maximum reading was regarded as definitive. The total of eight readings obtained was plotted as a calibration curve (Figure 3), which followed the classical Beer-Lambert form. The sensitivity in the linear region of the graph is 1.25 mg lanolin per unit absorbance.

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