WATER CONTENT AND ASH OF PLANTS 167 



the growth of the plant is restricted. Some plants, after 

 their growth has been checked by withholding calcium, 

 will show increased vigor within a few hours after 

 it is supplied. Calcium is assimilated in the early 

 stages of plant development. In wheat, for example, 

 80 per cent, is assimilated before the plant heads 

 out. Calcium assists in imparting hardiness to crops. 

 It does not accumulate in the seeds to such a great extent 

 as do other elements. Only about a tenth of the total 

 amount removed in grain crops is in the seeds, the re- 

 maining nine-tenths being present in the straw. Crops 

 grown on lime soils are usually well nourished, and are 

 more capable of withstanding unfavorable climatic condi- 

 tions as drought and early frosts than are crops not so 

 liberally supplied with lime. 



Experiment 42. Lime, CaO, in plant ash. Transfer the ash 

 from Experiment 40 to a beaker containing 5 cc. HC1 and 50 cc. 

 H 2 O ; heat ten minutes, filter, and divide into two portions. Save 

 portion for Experiment 44. Make one portion neutral with am- 

 monia, NH 4 OH. Add 5 cc. NH 4 C1 solution. To the solution, 

 add 5 cc. ammonium oxalate, (NH 4 ) 2 C 2 O 4 ; note the precipitate 

 which is calcium oxalate, CaC 2 O 4 . 



Into a separate test-tube put o.i gram CaCl 2 , add 5 cc. H 2 O and 

 a little HC1 until acid ; then nearly neutralize with NH 4 OH and 

 add NH 4 C1 and (NH 4 ) 2 C 2 O 4 . Compare this precipitate with that 

 from the clover ash. Observe, in this second test, that you 

 have taken a pure calcium salt, and that the same precipitate was 

 given as by the plant ash. Write the following reactions which 

 have taken place : CaC 2 O 4 -f Heat =? CaCO 3 + HC1 =? CaCl 2 -f 

 (NH 4 ) 2 C 2 4 =? 



216. Magnesium is also an essential element. It occurs 

 in all plants and farm crops in somewhat smaller amounts 



