By D. W. Gilchrist Shirlaw and J. E. Nichols (Auth.)
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Every little thing is made up of them, from the furthest reaches of the universe to this e-book that you simply carry on your palms, together with you. such as you, the weather have lives: personalities and attitudes, abilities and shortcomings, tales wealthy with which means. you might imagine of them because the inscrutable letters of the periodic desk yet you recognize them far better than you realize.
Gerd Fischer ist Autor der bekannten Lehrbücher "Lineare Algebra" und "Analytische Geometrie" und Professor am Mathematischen Institut der Universität Düsseldorf.
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1 ml of ammonium molybdate is added to the tube and the contents shaken. 3. 6 drops of the reducing reagent are added and the tube again shaken. 44 A PRACTICAL COURSE IN AGRICULTURAL CHEMISTRY 4. Two other solutions are similarly prepared, but in one 10 ml of 0-5 normal acetic acid and in the other 10 ml of 2-5 ppm standard phosphate are used instead of the soil extract. 5. All the tubes are allowed to stand for 15 min. 6. T h e test solutions are now each poured into a colorimeter tube. 7. T h e red filter, 670 ηιμ, is fitted to the colorimeter, which is set to zero with the tube containing acetic acid and the reagents.
ELECTROMETRIC DETERMINATION OF SOIL REACTION This is the most accurate method where a pH meter is available. Both laboratory and portable models are supplied, and in each case electrodes arc placed in a soil suspension 32 A PRACTICAL COURSE IN AGRICULTURAL CHEMISTRY or a soil paste; with modern instruments the reaction is read off directly from a scale. Various ratios of soil to water have been advocated: one of 1:2*5 was recommended by the International Society of Soil Science (1930) and is often adopted.
4 ml of distilled water are added and the tube and contents well shaken. 4. The turbidity developed is compared against turbidities of a blank, 10 ppm potash, and 20 ppm potash, prepared in a similar manner. T h e comparison of turbidities is most readily accomplished 55 THE ANALYSIS OF SOILS by moving the test-tubes against white background on which a black line has been drawn. A suitable piece of equipment is illustrated in Fig. §. FIG. 6. Turbidity stand for the determination of potash. TABLE 8.