Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER IV PHOSPHATIC MANURES TheJPhosphates of Calcium—The Early Use of Bones as Manure— Preparation of Bone Meal and Steamed Bone Flour—Dissolved Bones and Bone Compounds—The Discovery of Mineral Phosphates, Coprolites, Phosphorite, Phosphatic Guanos, Rock Phosphates—The Invention of Superphosphate, Lawes and Liebig—The Manufacture of Superphosphate— The Manufacture of Basic Slag—Nature of the Phosphoric Acid Compounds in Basic Slag: their Solubility in Dilute Acid Solutions—Basic Superphosphate—Wiborg Phosphate— Wolter Phosphate. Although the fertilising effect of bones, in common with most other substances of animal origin, had been known in an empirical way for a very long time, the efficacy was generally put down to the oil they contained, and it was only at the close of the eighteenth century that attention became fixed on the phosphoric acid. Lord Dundonald, in his Treatise on the Connection of Agriculture with Chemistry', published in 1795, had arrived at a very sound perception of the case. When treating of phosphate of lime, he writes that it "is contained in animal matters, such as bone, urine, shells, etc., in some sorts of limestone, and in vegetable substances, particularly in the gluten, or the vegeto.animal part of wheat and other grain. It is a saline compound, very insoluble. There is reason to believe a very considerable proportion of this nearly insoluble salt is contained in most fertile soils. . . . These alkaline phosphates (potash and soda) will be found to promote vegetation in a very great degree, the substance of which they are composed, viz., alkaline salts and phosphoric acid, are found in the ashes of most vegetables." Again, Kirwan writes in 1796 about the constituents of plants: " Phosphorated calx is found in greatest quantity in wh...