[Evaluation of the citric acid solubility of phosphorus of rock phosphates (Technical note)] | Caracterizacion de la solubilidad en acido citrico del fosforo de rocas-fosforicas (Nota de investigacion)

English. Citric acid solubility (CAS) of phosphorus from 52 raw rock phosphates sampled in 7 different states of Mexico was performed in order to compare two different methods and to detect the relationship of the rocks' color with their CAS. The fist method involved a double extraction of phosphorus: water and in diluted citric acid (2 %). The second method used only citric acid as the solvent. Samples were categorized according to their color in 5 groups: yellow, white, brown, gray and pink. The means for citric acid solubility of samples was 43.1+-16.6 % and 50.0+-19.3 % for the first and second extraction methods, respectively (p.01). This percentage is low since samples with less than 75 % solubility are considered to be inappropiate for animal feeding purposes. Color had a significant effect (p.01) on CAS. White samples were found to have the best solubility and gray samples the worst. The other 3 colors were intermediate. Because it extracts more soluble P and is easier to perform, the second method (the one that only uses citric acid as a solvent) is recommended

Spanish; Castilian. Se analizo la solubilidad citrica del fosforo (SCF) de 52 rocas fosforicas, muestreadas en 7 estados de la Republica, con objeto de comparar los resultados mediante 2 metodos y estudiar la relacion existente entre su color y la SCF. El primer metodo de analisis consistio en una doble solubilizacion del fosforo, en agua y en acido citrico al 2 %. En el segundo metodo, el fosforo fue solubilizado unicamente en acido citrico al 2 %. Dependiendo de su color, las rocas se agruparon en: amarillas, blancas, cafes, grises y rosadas. A cada color, se le asigno aleatoriamente un valor numerico. Los resultados promedio de SCF fueron 43.1+-16.2 % y 50.0+-19.3 % para el metodo de 2 y una solubilizacion, respectivamente (p0.01), sobre las SCF, obteniendose mejores porcentajes con las rocas blancas y peores con las grises. Las rocas cafes, rosadas y amarillas tuvieron una SCF intermedia. Habiendo solubilizando una mayor cantidad de fosforo y siendo mas sencillo de realizar, es recomendable medir la SCF mediante el metodo de una sola solubilizacion