Ferrous phosphate

The presence of nitrate as acelerator has a pronounced effect on the amount and composition of gas evolved from the work being treated (Table 15.8). It will be observed that hydrogen evolution drops to a very low figure with the zinc/nitrate baths. The formation of nitrite arises from decomposition of nitrate by reaction with primary ferrous phosphate to form ferric phosphate ... 

Temperatures reached during phosphate-based cleaning programs are only modest, and under these lower temperature conditions the passivated film consists of gamma iron oxide (yFe203) together with primary ferrous phosphate [Fe2H2(P04)2] and tertiary ferrous phosphate [Fe3(P04)2]. 

Gschwend, Ph. M and M. D. Reynolds (1987), "Monodisperse Ferrous Phosphate Colloids in an Anoxic Groundwater Plume", J. Contam. Hydro . 1/3, 309-327. 

In ihe coaling reaction, each 3 moles of iron or zinc liberates 4 moles of hydrogen ion. However, in the pickling reaction, 8 moles of hydrogen ion arc consumed. Thus, the pH at the metal interface rises, and insoluble tertiary ferrous phosphate and zinc phosphate crystallize on the iron surface. The coaling closest to the meta interface is largely iron phosphate, while that farther away is rich in zinc phosphate. 

Iron buildup in the bath is objectionable in the iron-removal equations above, it is seen that dissolved Fe+ can he removed by oxidation, slowly in air or more rapidly by peroxides or nitrite, as shown in the final equation. The irnn removed becomes ferric phosphate, while iron in the coating is ferrous phosphate. 

The converters, and afterwards the open hearths, in or on which the pig iron containing phosphide 6 was oxidised, are lined with lime or magnesia. The ferrous phosphate produced by oxidation, instead of being immediately reduced again by the excess of iron, is decomposed by the lime according to the equation... 

Gschwend, P.M. and Reynolds, M.D., Monodisperse ferrous phosphate colloids in an anoxic groundwater plume, J. Contam. Hydrol., 1, 309, 1987. 

Ludlamite is a green hydrated form of ferrous phosphate found in Cornwall1 and elsewhere. On heating it disintegrates into bluish green plates, m contradistinction to vivianite which turns white and exfoliates under similar treatment. 

A powder containing at least 90 per cent, of the octahydrated ferrous phosphate is obtained by mixing solutions of sodium acetate (2 parts), sodium phosphate (10 parts), and ferrous sulphate (8 parts), and allowing to stand in the absence of air for several days. The precipitate is collected on a calico filter and dried at 40° C.16 If the liquid... 

Ferrous metaphosphate, Fe(P03)2, is prepared by the action of fused metaphosphoric acid on ferrous phosphate, oxalate, or chloride, or even metallic iron, at red heat in a current of carbon dioxide. The salt is obtained as a white insoluble powder, unaffected by hydrochloric or nitric acid, but attacked by hot concentrated sulphuric acid.6... 

In Section 10.6 of the preceding chapter it was shown that tricresyl phosphate, a widely used organophosphorus additive, left an interaction film of ferrous phosphate on the steel surface that it lubricated. In terms of a mechanism generally applicable to the esters of phosphorus oxyacids, two reaction paths immediately suggest themselves. One is the thermal decomposition of the ester linkage, catalyzed by the activated metal interface ... 

Mandarino JA, Sturman BD, Corlett MI (1978) Satterlyite, a new hydroxyl-bearing ferrous phosphate from the Big Fish area, Yukon Territory. Can Mineral 16 411-413 Martini JEJ (1978) Sasaite, a new phosphate mineral from West Driefontein Cave, Transvaal, South Africa. Mineral Mag 42 401-404... 

Fig. 6-23. Experimental data on solubility product of ferrous phosphate. From P. C. Singer, /. Wafer Pollution Control Fed., 44 663 (1972). 1972 Water Pollution Control Federation, reprinted with permission.

Under oxidized conditions in mineral wetland soils, the coating of hydrated ferric oxides on silt or clay particles have occluded in them several forms of phosphate including ferric phosphate, aluminum phosphate, and calcium phosphate (Figure 9.32). As a result of anaerobic conditions, reduction of hydrated ferric oxide to more soluble ferrous hydroxide results in the release of these occluded phosphates. Calcium phosphate released in this manner is available to wetland plants, whereas the occluded ferric phosphate is probably not available to the plants until it has been reduced to more soluble ferrous phosphate. 

Sequential reduction of electron acceptors can have a significant effect on soluble phosphorus release. After a soil is flooded, it is expected that the amount of soluble P will increase. This is attributed to the anaerobic conditions occurring in the flooded soil and the various mechanisms of releasing phosphorus under those conditions. As shown in Figure 9.58, the amount of soluble phosphorus starts increasing after the third day of inundation, when almost the entire nitrate pool has been reduced, and consequently the reduction of manganese and iron contained in oxide minerals is already in process. On reduction of ferric oxide minerals, water-soluble and exchangeable concentrations of ferrous iron increase markedly. Thus, the dissolution of iron minerals is accompanied by increases in concentrations of both adsorbed and water-soluble phosphorus. Some of the ferrous ions react with the released phosphorus and precipitate to form new ferrous phosphate minerals. As the soil continues to be under anaerobic conditions, ferric ions are soon depleted and the reduction... 

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