176. 



Nature-Study Agriculture 



Packing- 

 house 

 fertilizers 



Dried 

 blood 



The 



nitrogen in 

 the air 



The 



electrical 

 method of 

 fixing 

 nitrogen 



The Haber 

 process; 

 fixing nitro- 

 gen under 

 pressure 



In large meat-packing establishments there are 

 enormous quantities of offal. The offal fat is made into 

 grease ; but the bones, horns, and hoofs (after the glue 

 products have been extracted), and the blood and animal 

 waste are cooked and dried for use as fertilizers. Of 

 these products the dried blood is the richest in nitrogen 

 and the quickest to give up its nutriment to plants. 



If plants were able to absorb nitrogen directly from 

 the air and use it as food, they would have an abundance, 

 for four fifths of the air is nitrogen. The air presses 

 down upon every square inch of surface with a weight 

 of nearly fifteen pounds. About four fifths of this 

 weight is due to nitrogen and this gives almost twelve 

 pounds as the weight of nitrogen upon each square inch. 

 As ordinary plants are unable to use this gas, chemists 

 have invented several methods for making it unite with 

 other elements in compounds suitable for plant-food 

 material. One of these methods consists in passing 

 strong electric sparks through the air, making nitrogen 

 and oxygen unite. From this compound a good fertilizer 

 can be made. In Norway, water power equal to the 

 strength of a quarter of a million horses is used to gen- 

 erate electricity for capturing nitrogen from the air. 



The latest and most efficient method of fixing nitro- 

 gen was invented by a scientist named Haber. In his 

 process hydrogen gas is mixed with nitrogen of the air, 

 and the gases are subjected to great pressure. They 

 unite to form ammonia, which is easily changed into 

 a good nitrogen fertilizer. This process is not limited 

 to countries having enormous water power, as the 

 electric method is. The machinery used can be driven 



