Dihydrogen Phosphate Groups Research Articles

Synthesis of new acrylic cation exchangers bearing pendent alkyl dihydrogen phosphate groups

Copolymerisation en emulsion inverse d'acrylamides portant les groupes lateraux du titre, avec le N[bis-hydroxymethyl)-1,1 hydroxy-2 ethyl] (meth) acrylamide et le N,N'-methylene diacrylamide(reticulant)

Interactions and space requirement of the phosphate head group of membrane lipids: The single crystal structures of a triclinic and a monoclinic form of hexadecyl-2-deoxyglycerophosphoric acid monohydrate

The crystal structures of a triclinic form (HPA1) and a monoclinic form (HPA2) of hexadecyl-2-deoxyglycerophosphoric acid monohydrate were determined by single crystal analysis. The unit cell dimensions for HPA1 are a = 4.75, b = 5.72, c = 44.36 A ̊ and α = 91.0, β = 101.5, γ = 100.5° (P 1 ) and for HPA2, a = 4.75, b = 5.72, c = 88.72 A ̊ and γ = 100.8° (P2 1). In both structures the molecules are fully extended and pack tail-to-tail in bilayers with tilting (47°) hydrocarbon chains. In HPA2, however, the chain tilt alternatingly changes direction in adjacent bilayers, giving rise to a doubled unit cell which spans two bilayers. The dihydrogen phosphate groups interact by hydrogen bonds and are arranged in rows. Laterally between these phosphate rows the water molecules are accommodated producing a compact two-dimensional network of hydrogen bonds. The packing cross-section in the layer plane of the dihydrogen phosphate monohydrate group is 26.7 Å 2 in both structures. The hydrocarbon chains pack according to the triclinic (T|) chain packing mode. In HPA2, however, the chain packing is somewhat less compact with accounts for a 2% increase in the molecular volume. In both structures the ether oxygen is accommodated into the hydrocarbon matrix without distortion of the chain packing.

On the selective etching of KDP crystals

The etching characteristics of [100] and [101] surfaces of KDP in water, alcohols, acetone, organic acids and in their mixtures are investigated. It is found that a fast dissolving solvent produces better contrasting dislocation etch pits and is insensitive to surface orientation. The results are briefly analysed from theoretical considerations. Finally, some comments are made on the composition of selective etchants used for the crystals of dihydrogen phosphate group by previous workers.

Crystalline cerium(IV) phosphates—I Preparation and characterization of crystalline compounds

The preparation of seven cerium(IV) phosphates, six of which new compounds, is described. The compounds were characterized by means of analytical, thermal, i.r., and X-ray methods. Five of the compounds belong to a series whose general formula is Ce(OH) x (PO 4) x (HPO 4) 2−2 x . y H 2O. Two of these can be characterized as being end members of the series, i.e. Ce(HPO 4) 2 and Ce(OH) 0·7(PO 4) 1·1 although the latter compound does not quite conform to the required stoichiometry. The remaining two compounds contain dihydrogen phosphate groups as well as orthophosphate and may be members of additional series.

The Lower Curie Point of Ferro-electric Salts

COMPARATIVELY little attention has been given to the behaviour of the group of ferro-electric salts analogous to potassium dihydrogen phosphate (KH2PO4) at the so-called ‘lower Curie point’. In this region dielectric measurements in an alternating field show a rapid decrease in the magnitude of the reversible polarization with decreasing temperature1. There has been indirect evidence that this can be attributed simply to the sharp rise in the coercive field, itself unexplained, which has been observed to accompany it, and that the domains of the crystal retain their high spontaneous polarization at lower temperatures. This concept of the ‘freezing-in’ of the electric moment has been supported by the lack of a specific heat anomaly as observed in this salt2, and in the case of potassium di-deuterium phosphate by the constancy of the saturation polarization as inferred from electro-optical measurements3, and by the absence of any change detectable by X-ray analysis; an angular deformation has been clearly shown by this method to accompany the onset of spontaneous polarization at the upper Curie point4. While in the Rochelle salt group the lower Curie point corresponds to a real disappearance of the spontaneous polarization5, no direct experimental evidence exists in any published work for the potassium dihydrogen phosphate group of ferro-electric salts.