39 



harmful to vegetation, especially tlie latter; but on 

 exposure of the gas lime for a considerable time to 

 the air they become changed to the useful sulphate. 

 The carbonate is of little value, and only the sul- 

 phate and the unchanged lime can be counted on as 

 of any use . 



' 'I do not consider the material as of much value 

 for fertilizing purposes ; for after due exposure to 

 the air, to render the sulphide and the sulphite 

 harmless, the unchanged lime will also, in this time, 

 be converted to carbonate, so that only the sulphate 

 is left to be useful ; and if I were going to use land 

 plaster, I would prefer to buy it outright and know 

 what I have. 



"As an insecticide its use would be dangerous, 

 because of its effect on the plant itself, unless it has 

 been well aired, and as for its usefulness in this re- 

 spect after having been thus aired, it would be same 

 as a mixture of plaster and chalk." 



Besides these compounds (carbonate and nitrate), 

 lime enters into 'still other important combinations, 

 especially with phosphoric acid, forming phosphate 

 of lime; and with sulphuric acid, forming sulphate 

 of lime (gypsum). More will be said about these 

 further on. 



The aristocratic name given to the simple com- 

 pound of the element chlorine, a poisonous gas, 

 with the element sodium is "chloride of sodium." 

 Ordinarily it is called salt. Both of its 



^Tau!^ component parts can serve as plant food. 

 The oxide of the metal sodium is soda. 

 Some plants, like beets, turnips, etc., contain con- 

 siderable chlorine and still more of soda. For this 

 reason the application of this chloride of sodium 

 (common salt) is found to be quite beneficial for such 



