DIFFERENTIAL EFFECTS OF VARIOUS CALCIUM CARRIERS UPON TRANSITIONS IN PHOSPHATE MIXTURES

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Abstract
Findings through 30 years are briefed. Dry limestone and dolomite proved inert in mixtures with ammoniacal phosphates. As registered through CO2 evolution, progressions in the neutralization of superphosphate in mixtures with limestone and dolomite showed up to 17% loss in P2O5 availability in the limestone mixtures, and virtually none in those with dolomite. In multiple ratios of aqueous 24-hr. suspensions of superphosphate and limestone, evolutions of CO2 registered complete transition to diCa and 3/4 replacement of the 3d H, whereas the dolomite produced only diCa-and diMg phosphates. In dilute H2O systems, monocalcium phosphate reacted on limestone and on dolomite and generated dibasic forms, whereas the Ca-Mono was inert towards those solids when monoMg phosphate was included; in slurries, however, the jointly included monophosphates were reactant on both limestone and dolomite. In moist mixtures with di-calcium phosphate, limestone induced 60% transitions to the tertiary and generated 9% of citrate-insoluble, against 20% transition and 0.4% generation by dolomite, during 13 months. In 10-ton mixtures of 2 of wetted limestone or dolomite (dry basis), with 1 of superphosphate, setting was prevented and P2O5 reversions were held to minimum by re-workings, or by several daily up-endings of the immediately bagged mixtures. Ca silicate in mixes proved compatible with superphosphate and the liberated SiO2 served as conditioner and as desiccant. Fluorine-free Ca silicate additions converted superphosphate slurries to workable solids, without detriment to P2O5 availability. In superphosphate mixtures with Ca silicate slag, quenched and unquenched, anhydrous diCa phosphate developed in the dry without detriment, but fluorophosphate formation was registered by the high "citrate-insoluble" that developed in moist mixtures. Powdery defluorinated rock phosphate induced citrate insolubility in mixtures with superphosphate, whereas fluorine-free fused tricalcium phosphate of low F content did not. In superphosphate mixtures, selectively calcined dolomite induced diCa phosphate, with residues of MgO, but it generated mono- and dimagnesium phosphates in aqueous systems and during analytical extraction procedures. Although fresh mixtures of slag and superphosphate proved effective upon immediate incorporation, they suffered in effectiveness through decrease in P2O5 availability when allowed to age. Joint usage proved efficacious, however, when slagged soils were phosphated and gave results often superior to those from equivalent inputs of super and limestone. Ca silicate invariably proved more effective than the carbonate, in super mixtures and in the soil. Ca fluoride exerted no deleterious effect upon P2O6 availability in the soil and showed no nutrient value.

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