The routine determination of exchangeable bases in soils by the lundegardh flame spectrographic method

Considerable changes have been made in Mitchell's methods for spectrographic determination of exchangeable bases in soils. The following paper describes these modifications which include ( a ) the use of an automatic leaching apparatus for extracting the soils with ammonium acetate: this economizes in material and time and permits an approximate estimation of exchangeable hydrogen to be made; ( b ) the use of aqua regia for destroying organic matter; ( c ) a combination of new dilutions and new standards with the use of a metol developer for the plate: this considerably extends the range of soils dealt with by the standard routine; ( d ) a modification of the plate holder, enabling 88 spectrograms to be recorded on one 5‐in. × 4‐in. plate; and ( e ) a method of plotting working curves from the photometric data which is considered to have several advantages over those in general use.