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The Use of Perchloric Acid in the Determination of Total Phosphorus in Soils
Author(s) -
Volk Garth W.,
Jones Randall
Publication year - 1938
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1938.036159950002000c0028x
Subject(s) - perchloric acid , citation , soil water , library science , mathematics , chemistry , computer science , environmental science , soil science , organic chemistry
The determination of total phosphorus in soils and organic materials has been studied by different investigators, and several methods of digestion or fusion have been proposed to change the phosphorus into a soluble form. Emmert (£) reported a method of digestion in which a mixture of H2S04 and NaC103 was used to destroy soil organic matter. His results indicate that 3.0 to 21% more phosphorus was obtained from the soil by using this mixture than by the official magnesium nitrate method (l). King (4) pointed out that perchloric acid is an excellent oxidizing agent for organic materials when heated to high temperatures and proposed a method in which this acid was used to destroy organic matter in plant materials. The use of perchloric acid for the oxidation of organic matter in forage was further developed by Gieseking, Snider, and Getz (3). In order to reduce the danger of explosion, samples were pretreated with HN03 and finally digested with a mixture of HN03 and HC104. Other methods which have been recommended include mixtures of sulphuric acid and hydrogen peroxide, sulphuric acid and nitric acid, nitric acid and nitrates, fusion by alkaline mixtures such as sodium peroxide, and by dry ignition for the destruction of organic matter. These methods are not entirely satisfactory. Two factors, namely, the incomplete extraction of the phosphorus, and the presence of colloidal silica, affect the accuracy of methods which have been proposed for the determination of total phosphorus in soils. Separate treatments to destroy organic matter and remove silica from solution increase the time required to complete an analysis. Since perchloric acid will oxidize organic matter and dehydrate silica (5), it is possible that it may be used to combine the two processes into a single operation. The losses occurring from incomplete extraction of the fused mass would be eliminated, because there is no introduction of large amounts of fusing material which usually forms a hard fused mass or cake. The Effect of the Perchlorate Ion and Temperature on the Precipitation of Phosphorus as Ammonium Phosphomolybdate