In a reciprocal action, more phosphate application to soils stimulated increasing research on the conditions and reactions obtaining in the complex and varying compositions called soil. The findings of bacteriologists made it clear that physics and chemistry had to be amplified by biology for a real understanding of fertilizer effects. After 1900, for example, Julius Stoklasa (1857-1936) pointed out that bacterial action in soil solubilizes water-insoluble phosphates and makes them available to the plants.[26]
Figure 9.—Florida river-pebble phosphate mining. (From Carroll D. Wright, The Phosphate Industry of the United States …, plate facing page 64.)
The insight into the importance of phosphorus in organisms, especially since Liebig’s time, is reflected in the work of Friedrich Nietzsche (1844-1900). This “re-valuator of all values” who modestly said of himself: “I am dynamite!” once explained the human temperaments as caused by the inorganic salts they contain: “The differences in temperament are perhaps caused more by the different distribution and quantities of the inorganic salts than by everything else. Bilious people have too little sodium sulfate, the melancholics are lacking in potassium sulfate and phosphate; too little calcium phosphate in the phlegmatics. Courageous natures have an excess of iron phosphate.” (See volume 12 of Nietzsche’s Works, edit. Naumann-Kröner, Leipzig, 1886.) In this strange association of inorganic salts with human temperaments, the role of iron phosphate as a producer of courage is particularly interesting. What would a modern philosopher conclude if he followed the development of insight into the composition and function of complex phosphate compounds in organisms?
From Inorganic to Organic Phosphates
By the middle of the 19th century, the source of phosphorus in natural phosphates and the chemistry of its oxidation products had been established. The main difficulty that had to be overcome was that these oxidation products existed in so many forms, not only several stages of oxidation, but, in addition, aggregations and condensations of the phosphoric acids. Once the fundamental chemistry of these acids was elucidated, the attention of chemists and physiologists turned to the task of finding the actual state in which phosphorus compounds were present in the organisms. It had been a great advance when it had been shown that plants need phosphates in their soil. This led to the next question concerning the materials in the body of the plant for which phosphates were being used and into which they were incorporated. Similarly, the knowledge that animals attain their phosphates from the digested plant food called, in the next step of scientific inquiry, for information on the nature of phosphates produced from this source.
The method used in this inquiry was to subject anatomically separated parts of the organisms to chemical separations. The means for such separations had to be more gentle than the strong heat and destructive chemicals that had been considered adequate up to then. The interpretation of the new results naturally relied on the general advance of chemistry, the development of new methods for isolating substances of little stability, of new concepts concerning the arrangements of atoms in the molecules, and of new apparatus to measure their rates of change.