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PRINCIPAL HENRY A. MIERS AND MISS FLORENCE ISAAC ON THE 



solution were watched by the method of total reflection within the prism. About 

 half of the experiments were made with the smaller goniometer which was used in all 

 the earlier work referred to above, but in the remainder of the experiments the acid 

 solutions were examined by means of a new inverted goniometer (fig. 4), specially 



Fig. 4. 



designed for this work, the trough of which contains a much larger quantity of 

 solution than the smaller instrument (see ' Journ. Chem. Soc.,' 1908, 93, p. 385, where 

 this goniometer is briefly described, and the method of regulating the temperature of 

 the solution by a stream of hot or cold water flowing over the outer surface of the 

 trough is explained) The first step in the present investigation was to plot on the 



