An investigation of the kinetics of the formation of permanganate from divalent manganese using periodic acid as oxidant

1. The rate at which permanganate is produced when divalent manganese is oxidized with potassium periodate has been followed absorptiometrically in sulphuric and nutric acid solutions Under certain conditions the reaction is of the first order with first order autocatalysis. 2. An expression has been derived for the velocity constant, which is used to compare the speed of oxidation in solutions of various acidities at various temperatures. The velocity is a minimum with 1.5 M acid, but increases in either stronger or weaker acid solutions.. An increase in velocity is accompanied by a decrease in the quantity of permanganate produced from a given quantity of divalent manganese. 3. It has been deduced that divalent manganese is only slowly oxidized by periodate unless a catalyst (such as the surfacc of metallic platinum) is present. The natural catalyst for the reaction is quadrivalent manganese, produced at one stage in tlie oxidation. A detailed account of the probable mechanism of the oxidation is suggested, having regard to the thermodynamical properties of the molecules involved. 4. Suitable conditions for an absorptiometric method are recommended. Metallic platinum is useful for reducing the very long induction period found wlien only traces of manganese are present.     

Helices versus zigzag chains: one-dimensional coordination polymers of Ag(I) and Bis(4-pyridyl)amine

Five one-dimensional coordination polymers were prepared by the reaction of a bent bridging ligand, bis(4-pyridyl)amine (bpa), with an extensive series of AgX salts (X = CF3SO3, PF6, ClO4, NO3). The 1D polymer networks formed with AgCF3SO3 (1), AgPF6 (2.MeCN), and AgClO4 (3.2MeCN) all incorporated MeCN and were found to adopt a zigzag arrangement. The networks formed with AgClO4 (4) and AgNO3 (5) did not contain any solvent and adopted a single-stranded helical arrangement. Two-dimensional H-bonding networks were formed for 1 and 3.2MeCN, with network topologies 4.8(2) and (4, 4), respectively, whereas three-dimensional H-bonded networks of helices were formed for 4, showing an (8, 3)-a network topology, and 5, showing the topology of the alpha-polonium net. The three-dimensional networks both exhibited 4-fold interpenetration. The NO3- anion in 5 appeared to be acting as a template for the 3D structure.     

Surface core level shifts on InP(110): Use of Sb overlayers

The surface core level shift of the P2p from a clean InP(110) surface has been studied by use of the Sb overlayer. It is shown that the nonreactive Sb overlayer removes the surface core level shift and does not introduce any other component. The unique possibility to separately characterize the bulk component allows a precise determination of the surface core level shift. We show that the surface P2p core level is shifted to lower binding energy by −0.29 eV, while an opposite and nearly equal in magnitude +0.30 eV shift is established for the In4d.     

On the collision density in recoil hot atom systems. Effect of reactive events

Characteristics of the collisional distribution function for reactive hot atoms in nuclear recoil systems are examined and illustrated for the T + H₂ system both unmoderated and moderated with argon. Reaction induced extrema are evident in the collision density of the unmoderated case. For this system depletion of hot atoms from the collisional distribution function due to reactive events is reflected significantly in the product yields even at high moderation.     

Nature of the energy dependent self energy for photoelectrons in copper

New high resolution ultraviolet photoemission energy distributions (EDCs) from copper are found to agree best with the calculations of Williams et al., using the Chodorow potential, if an energy dependent shift is made between the experimental and calculated EDCs. It is argued that this shift is most probably due to an energy dependent self energy as discussed by Lundqvist and others.     

Femtosecond laser-induced fragmentation and cluster formation studies of solid phase trinitrotoluene using time-of-flight mass spectrometry

We use surface-femtosecond laser mass spectrometry to study the fragments/products formed when trinitrotoluene (TNT) is subjected to femtosecond laser pulse irradiation and to study the conditions under which TNT is removed from a solid surface. In surface-femtosecond laser mass spectrometry a compound is deposited on a solid substrate and is desorbed into vacuum by femtosecond irradiation forming a plume of ionized and neutral species. The positive or negative ions are then accelerated by an electric potential and allowed to drift in the field-free region of a time-of-flight mass spectrometer. The mass-to-charge ratio of each ion is obtained using the value of the accelerating field and the ion flight time. In this paper we report femtosecond laser mass spectra for the positive ions formed by desorbing TNT with 130 fs pulses centered at 800 nm for fluences ranging from 7 to 1.4 × 10⁵ J/m². The conditions under which TNT removal and ionization occur are also discussed.     

石荠苧不同药用部位总黄酮及微量元素含量的测定

采用分光光度法测定了石荠芋不同药用部位总黄酮的含量,采用电感耦合等离子发射光谱法测定了其中微量元素的含量。结果表明,叶中总黄酮含量最高,根次之,茎最少;根、茎、叶中均含有Cu、Fe、Mn、Zn、Co等多种人体必需的微量元素,其中Fe含量最高,且叶中明显高于根、茎;3个部位均未检出有害重金属As,而Hg、Pb含量均未超标。该结果可为石荠芋不同药用部位的利用和药材的开发提供科学依据。