38 NITRATES OF POTASH AND SODA. 



culiar smell, and being extremely sour and corrosive. 

 a. When strong, it destroys the skin, and in all cases 

 turns it of a deep yellow color which can not be re- 

 moved by washing, b. It eats holes through cloth, 

 turning it to a bright red color, c. Like ammonia 

 and the acids before mentioned, we do not find it 

 naturally as a pure substance; it is always combined 

 with something else. One of the most common forms 

 is nitrate of potash, or saltpetre. Nitrate of soda is 

 also often found in nature, d. In South America, this 

 latter is so abundant as to be brought away by the 

 shipload. It is in the form of such compounds as these 

 that nitric acid is present in the soil. They are easily 

 dissolved in water, can be received into the circulation 

 of plants through their roots, and can furnish nitrogen 

 as readily as ammonia. 



In some situations more nitrogen is received into 

 the plant as ammonia, than from any other source; in 

 others, more as nitric acid. I consider that this is 

 owing simply to the quantity of either that may be 

 present in different localities. Both kinds of manure 

 produce remarkable results when applied to the soil of 

 most farms; and these effects are nearly or quite 

 identical in appearance, showing that in both cases 

 nitrogen caused the improvement, and that between 

 these two forms of applying it there is little choice. 



