“Perhaps so,” said I, “though there is nothing gained by mixing earth or ashes with them, except in securing a more even distribution. And if I was going to sow them myself, I would much prefer sowing them unmixed. Any man who can sow wheat or barley can sow sulphate of ammonia or nitrate of soda.”
“Lawes and Gilbert,” said the Deacon, “used sulphate and muriate of ammonia, and in one or two instances the carbonate of ammonia. Which is the best?”
“The one that will furnish ammonia or nitrogen at the cheapest rate,” said the Doctor, “is the best to use. The muriate of ammonia contains the most ammonia, but the sulphate, in proportion to the ammonia, is cheaper than the muriate, and far cheaper than the carbonate.”
Carbonate of ammonia contains 21½ per cent of ammonia.
Sulphate of ammonia contains 25¾ per cent of ammonia = 21⅕ of nitrogen.
Muriate of ammonia contains 31 per cent of ammonia = 25½ of nitrogen.
Nitrate of soda contains 16⅖ per cent of nitrogen.
Nitrate of potash, 13¾ per cent of nitrogen.
From these figures you can ascertain, when you know the price of each, which is the cheapest source of nitrogen.
“True,” said I, “but it must be understood that these figures represent the composition of a pure article. The commercial sulphate of ammonia, and nitrate of soda, would usually contain 10 per cent of impurities. Lawes and Gilbert, who have certainly had much experience, and doubtless get the best commercial articles, state that a mixture of equal parts sulphate and muriate of ammonia contains about 25 per cent of ammonia. According to the figures given by the Doctor, the mixture would contain, if pure, over 28 per cent of ammonia. In other words, 90 lbs. of the pure article contains as much as 100 lbs. of the commercial article.”