E. J. Russell and J. A. Prescott 



85 



The mechanical and chemical analyses of these soils are given in 

 Table I. 



Table I. Mechanical analyses of soils. 



Chemical analysis of the soils. 



The method of extraction of the soil ivith the acid. A special feature 

 of our experiments is that the extraction was carried out at constant 

 temperature. The apparatus is shown in Fig. 8. A bicycle wheel is 

 mounted at the apex of a triangular wooden stand, which can either 

 rest on the floor, holding the wheel upwards, or else on the top rim of 

 the thermostat, holding the wheel downwards in the water. The wheel 

 is fitted with stout wooden clips enabling it to carry eight Winchester 

 pint bottles. As a preliminary to each experiment 100 gms. of soil 

 and a volume of distilled water sufficient to make one litre of dilute acid 

 are placed in each bottle, which is then closed with a rubber stopper; 

 the bottles are fixed on the wheel, put into the thermostat, and rotated 

 by means of a hot air motor for an hour, by which time the contents 

 have attained the temperature of the thermostat (23° C). Then the 

 bottles are lifted out, the requisite quantity of strong acid (2 N) is added 



