WATER-ABSORPTION AND TRANSPIRATION. 



107 



dried substance, (2) the metallic oxides, the acids, and 

 chlorine in the ash itself. 



Note the striking difference between the seeds and the 

 straw (stalks and leaves) of Cereals and Leguminous plants 

 in the proportion of more important (e.g. magnesium) and 

 less important (e.g. silicon) elements. 



141. Ash Analysis. The chief elements to be tested 

 for, in analysing the ash of plants, are calcium, potassium, 

 magnesium, phosphorus, sulphur (the two latter being present 

 as acids). The ash should not be heated so strongly as to 

 make it burst into flame. 



(a) Is the ash soluble in (1) water, (2) dilute hydrochloric acid, (3) 

 strong hydrochloric acid ? Find out in each case by boiling some of the 

 ash in a test-tube with water or acid, allowing the undissolved part to 

 subside and evaporating some of the liquid, or heating it to dryness, 

 on a watch-glass or evaporating-dish. The insoluble residue, after treat- 

 ment with strong acid, contains chiefly silica. 



