Sept. lo, 191 7 



Formation of ''Black Alkali" 



563 



up with distilled water and allowed to come to equilibrium, gave an 

 extract that would show color with phenolphthalein upon boiling. This 

 soil, however, would not visibly effervesce with dilute acid. It contained 



S /O /S .£>0 ^5 30 3S ■'fO 03 SO 55 60 

 /=^/? C£>V7- AO/>/Oj 



Fig. 14.— Graphs showing the eSect of sodium nitrate on the solubility of calcium in soil. 



just enough calcium carbonate or soluble silicates to make it basic in 

 character. It contained 0.30 per cent of total calcium oxid on digestion 

 with strong hydrochloric acid (specific gravity 1.115) and 0.83 per cent 

 of humus. Part of the soil was taken and 2 per cent of its weight of 



c ^ /c? y^ ^o <?.5" 30 



Fig. 15. — Graphs showing the effect of sodium chlorid on the solubility of calcium in soil. 



calcium carbonate added and mixed with it. Portions of the original 

 soil and also the soil to which the calcium carbonate had been added 

 were shaken up with graduated solutions of each of the three salts 

 sodium nitrate, sodium chlorid, and sodium sulphate and mixtures of 



