66 PRACTICAL FARM CHEMISTRY. 



the habit of speaking of ammonia as one of the chief 

 plant foods. We have seen that ammonia is the com- 

 pound hydrogen-nitrogen, each seventeen pounds of it 

 containing fourteen pounds of the nitrogen, which we 

 want, and three pounds of hydrogen, which we care 

 little about. As an element of plant food, therefore, 

 it were much better if we would confine ourselves to 

 the proper term, nitrogen, rather than make a con- 

 fusing mess of it by wrongfully substituting for it 

 the name of the compound ammonia, as is so often 

 done in common farm parlance. In older works, 

 and occasionally in the columns of our farm papers, 

 we come across the term "potential ammonia." This 

 means the amount of ammonia which the nitrogen, 

 in whatever form it appears, might produce by fer- 

 mentation. I think we should dispense with the 

 term altogether. Fertilizer manufacturers, in giving 

 the legally demanded analysis on outside of bags, 

 often prefer to give the percentage of ammonia 

 rather than in nitrogen. It may give a better show- 

 ing to pat it five per cent ammonia instead of four 

 per cent nitrogen; but the only proper way to put it 

 would be, "four per cent nitrogen in ammonia" (or in 

 nitrates, as the case may be), or leave out the source 

 or form entirely, and simply say, "four per cent 

 nitrogen." Then we know something about what we 

 have before us. 



Before going into the open market to look up our 

 sources of supply, we should learn something of the 

 character of the goods, and of the prices at which 

 they may be purchased. These prices are subject 

 to fluctuations, as are those of other articles of com- 

 merce, according to the disposition of the individual 

 dealer, but chiefly in obedience to the laws of sup- 

 ply and demand. In recent years the tendency of 



