CHAPTER XII. 



NITROGENOUS MANURES. 



The most widely distributed nitrogenous manures are nitrate of 

 soda (Chili saltpetre) and sulphate of ammonia. A third class of 

 purely nitrogenous manures is that represented by animal waste. 

 These (latter) products are of considerable agricultural importance^ 

 although the manure trade does not seem to take them sufficiently 

 into account. These three forms of nitrogenized manures are not 

 only differentiated by their chemical composition, but by their mode 

 of action in the soil. They form therefore three distinct classes, 

 which will now be examined. 



Nitrate of Soda. — Nitric acid compounds have been known for 

 a long period. It is probable, according to Herapath, that the 

 ancient Egyptians used nitrate of silver to make their inscriptions 

 on the bands in which they wrapped their dead ; it is the same 

 chemical compound as that known as infernal stone, which is 

 used to mark linen and the skin. So far back as the eighth 

 century of the Christian era, Geber and Marcus described a body 

 which they called salpetrce, which corresponds with saltpetre, with 

 nitrate of soda. In the twelfth century, Raymond Lulle called this 

 body salnitri. Since then the term saltpetre has been used to 

 designate nitrate of potash, whilst nitrate of soda is called Chili 

 saltpetre, or nitre, in Great Britain. 



Nitric Acid consists of nitrogen, oxygen, and hydrogen ; its. 

 chemical formula is HNO3. It thus contains fourteen parts of 

 nitrogen (22-2 per cent), forty-eight parts of oxygen (76-19 per cent), 

 and one part of hydrogen (1 'oQ per cent). It forms a very caustic 

 fuming liquid (attacking organic matter, strongly burning the skin). 

 In the concentrated state it has a density of 1-52 (104° Tw.), but 

 the commercial acid is generally much weaker : D = 1 '20 to 1 '4 

 (40" to 80° Tw.). It decomposes easily. It gives up a portion 

 of its oxygen to oxidizable bodies, such as carbon, sulphur, sulphur- 

 ous acid, and then passes to less highly oxidized states. Metallic 

 zinc reduces dilute nitric acid, and converts it into nitrate of 

 ammonia. With bases it forms salts, which with the exception of 

 some basic metallic salts, are soluble in water. Nitric acid is formed 

 almost exclusively by the oxidation of ammonia, or of nitrogenous 

 matter of animal origin, under the action of the air in presence of 



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