164 CONTRIBUTIONS TO OUR KNOWLKDGE OP SOIL-FERTILITY, xvi., 



more is absorbed by the sterilised than by the unsterilised mould. 

 The organic matter has absorbed from 12 to 13% lime [CaO], and 

 about 90% of the total was absorbed within two days. 



The difference in the amount of base absorbed from the 

 hydrate, as against the bicarbonate, led to a test being made 

 with bicarl)onate of magnesia. A quantity of freshly precipitated 

 and waslied carbonate was suspended in water, and a current of 

 carbon dioxide was passed through for several hours. The solu- 

 tion was filtered, and 200 c.c were added to 4 grams of soil in 

 stoppered bottles. The solution of bicarbonate of magnesia was 

 approximately twelfth normal The bottles were shaken fre- 

 quently, and the portions abstracted from day to day and boiled 

 with an excess of N/20 sulphuric acid for ten minutes, and 

 titrated with ]S'/20 soda in presence of phenolphthalein. 



Magnesium bicarbonate'— l^ovmal alkali, in c.c, absorbed by 

 100 grams of dry organic matter. 



The numbers are closely akin to those obtained with calcium 

 bicarbonate, and much under the tests with lime-water. 



Baryta-water. — The action of lime-water was controlled by a 

 test made with 'baryta- water, in which 300 c.c. of approximately 

 N/15 alkali were added to each 4-gram-portion of mould. 



Normal alkali, in c.c , absorbed by 100 grams of dry organic 

 matter. 



These numbers run closely with those of the lime-water test 



