514 Scientific Proceedings, Royal Dublin Society. 



The change in solubility of soil constituents brought about by heat was 

 studied by two methods : — 



I. The depression of freezing-point of a series of extracts from heated 

 soil samples was determined. 



II. The electrical conductivities of the extracts were determined. 

 From these results an approximation to the depression of freezing-point 

 due to electrolytes was calculated. 



The soil with which the experiments were made was taken from a depth 

 of not more than six inches from the surface, and was freed as far as possible 

 from organic matter, plant-stems, leaves, worms, etc. The soil was then 

 passed through a sieve of quarter-inch mesh to remove large pebbles and hard 

 lumps. 



Small flower-pots, each holding about 350 gms. of soil were used for the 

 heating. Each sample was heated separately in an air-oven during a period 

 of not less than two hours ; the temperature was noted by a thermometer 

 placed in the soil, and was as far as possible kept constant during the period 

 of heating. Seaver and Clark (6) have shown tliat the duration of heating 

 after two hours lias but little effect on the amount of soluble material. 



Samples of soil were heated in this way at temperatures between 60° and 

 150°. Each sample was allowed to cool during twenty-four hours. An 

 extract was obtained in each case by placing the flower-pot on a retort stand 

 over a filter funnel witli paper, which dipped into a clean flask. The same 

 volume of distilled water was poured slowly over each sample. When the soil 

 was saturated, the water dripped through into the filter and appeared as a 

 brownish liquid in the flask. To prevent bacterial growth a few drops of 

 toluene were added to each solution, and the flask closed with a cork. 



Reaction to litmus. — The reaction of the solutions to litmus was tested in 

 each case, and found to be neutral. 



Colour of the solutions. — The range of coloration in the solutions was 

 marked. An extract from unheated soil was practically colourless ; the others 

 varied from a faint brownish yellow colour in that heated at 60° to a very 

 deep brown in that heated at 150°. 



Determination of depression of freezing-point. — The depression of freezing- 

 point of each solution was then determined by means of Beckmann's 

 apparatus. The freezing mixture was kept at a temperature of -2°, and 

 allowance was made for the depression due to dissolved toluene. 



