LEY 
read on the scale (J). At the same time the temperature is read on the 
thermometer. 
The instrument should be tested first with water and its accuracy es- 
tablished thereby: Ref. Ind. of water at 20° being 1.3330. The substance 
to be examined should be at about the same temperature at which the 
readings are to be made. Therefore waiting a few minutes after applying 
the liquid to the prism, it could be considered that this is at the same 
temperature. 
Tables have been prepared fer converting the refractometer read- 
ings to dry substance or per cent. of moisture. To some of these pre- 
vious reference has been made. Hugh Main, in the International Sugar 
Journal of 1907, Vol. 9, page 481, gives a table covering this. The readings 
are to be made at 20° C. Geerligs has published a table also for dry 
substance from the refractive index. The temperature of the reading is 
28° C. and he has also prepared a table for corrections for other tem- 
peratures than 28°. These are now given: 
