M. Steinberg

Infrared study of the thermal treatment of sepiolite and palygorskite saturated with organic amines

Abstract Butylamine (BA), pyridine (PY) and 2,4,6-trimethylpyridine (TMP) were adsorbed by sepiolite and palygorskite under reflux. The adsorption and the thermal stability of the organo-clay complexes were studied by IR thermospectrometry. In this technique KBr disks of the organo-clay complexes were heated to 100, 200, 300 and 400°C and IR spectra were recorded after each thermal treatment. The spectra proved that the adsorbed amines were located in the channels, replacing part of the zeolitic and bound water. The three amines were hydrogen bonded to the zeolitic water, Associations were also obtained between BA or PY and bound water in sepiolite but not in palygorskite and not with TMP. Small amounts of adsorbed BA and TMP were protonated. During the thermal treatment of the organo-clay, associations were formed between BA or PY and octahedral Mg exposed to the channel. From the thermal study it can be concluded that hydrophobicity of the clays increases and their thermal stability decreases as a result of the adsorption of the organic bases.

The study of oxygen sorption on cerium(IV) oxide by electron spin resonance

Abstract The presence of paramagnetic species on the surface of cerium(IV) oxide prepared by the thermal decomposition of the oxalate at low temperatures (375°) was shown by ESR. The sorption of oxygen at room temperature showed a new signal having g⊥ = 2.0137 and g| = 2.0312. This signal is ascribed to the formation of the anionic radical O2− on the surface. The origin of the paramagnetic species is ascribed to quasi-free electrons in the n-type non-stoichiometric cerium(IV) oxide.

THERMAL DECOMPOSITION OF THE LIGHT RARE EARTH OXALATES

Abstract The thermal decomposition of the light rare earth oxalates was studied in vacuum in the temperature range 340–440°C. The behaviour of the whole group (with the exception of europium oxalate) was analogous to that of lanthanum oxalate. The relative order of stability, as well as that of the intermediate normal and basic carbonates, is: Gd > Sm > Nd > La > Pr > Ce. The carbon monoxide, initially formed by the decomposition of the oxalates, underwent disproportionation. The degree of disproportionation was highest in the case of cerous oxalate (72 per cent), and lowest in the case of gadolinium oxalate (58 per cent), decreasing in reverse of the order of stability, with lanthanum and praseodymium changing places.

Thermal decomposition of europium(III) oxalate

Abstract It is shown that the first step in the thermal decomposition of europium(III) oxalate leads to reduction to the divalent state. In an oxidizing atmosphere the europium is reoxidized and continues decomposing gradually to Eu2O3 at 390°. In an atmosphere of CO2, Eu(II) Ox is stabilized at 320°. In vacuum, Eu(II)CO3 admixed with carbon (originating in disproportionation of CO) is obtained in the temperature range 360–420°. A unified mechanism for the decomposition of oxalates is proposed, in which a trace of carbon monoxide acts as catalytic agent in the reductive decomposition of oxalates of reducible metal ions.

Thermal analysis study of the adsorption of D2O by sepiolite and palygorskite

Abstract D 2 O treated sepiolite and-palygorskite were studied by DTA, TG and EGA. The adsorption was carried out by wetting the clays with D 2 O prior and after heating sepiolite to 430 and 600°C, and palygorskite to 360 and 600°C. Optimal conditions for adsorption of D 2 O are obtained after the temperate heating. Heating to 600°C blocked the porous structure and the adsorption took place on the external surface. Gas evolution curves showed that HDO is evolved during the recrystallization stage of sepiolite but not of palygorskite. It appears that during the first stages of dehydroxylation of sepiolite deuterium is trapped by the amorphous meta sepiolite and is released at higher temperatures during the recrystallization stage. It was concluded that the second stage of dehydroxylation of sepiolite is not associated with the decomposition of residual TOT units but results from the decomposition of secondary units which have been formed during the first stage of the dehydroxylation of this clay.

The preparation of cerium(III) aluminate at lower temperatures: IR, X-ray and electron spin resonance study

Abstract Cerium(III) aluminate was prepared at lower temperatures than reported previously by the citric acid method, in vacuum (formation started at 1393 K) and in hydrogen (formation started at 1273 K). The reaction was followed by IR, electron spin resonance, X-ray techniques and magnetic measurements. It is proposed that an intermediate species assigned as O2− is present.

Reaction of ethylene with oxygen on a Pt/CeO2 catalyst

Abstract A new pathway is suggested for the reaction of ethylene and oxygen. The catalyst used was Pt CeO 2 . The products obtained in addition to carbon monoxide, carbon dioxide, and water were methane and ethane which were formed by the hydrogenation of either carbon monoxide or ethylene. Electron spin resonance was used to show the role performed by lattice oxygen.

Characterization of Gunshot Residues by X-Ray Diffraction

The application of X-ray diffraction complemented by scanning electron microscopy and energy dispersive X-ray analysis to the characterization of gunshot residues is reported. Lead in the metallic form is found to be the main constituent of all gunshot residues tested. Several mechanisms are proposed to explain the appearance of lead in the metallic state as well as the formation of gunshot residue.

Thermogravimetric and differential thermal analysis of europiumIII oxalate and some europiumII salts

The thermal analysis curves of Eu/sub 2/(C/sub 2/O/sub 4/)/sub 3/, EuC/ sub 2/O /sub 4/, and EuCO/sub 3/ exhibit prominent exothermic peaks in the region of 420 deg because of the oxidation of europium/sup (II)/ to europium/sup (III)/. The first step in the decomposition of Eu/sub 2/(C/sub 2/O/sub 4/)/sub 3/, after completion of dehydration, is Eu/sub 2/(C/sub 2/O/sub 4/)/sub 3/ plus or minus / sub 2/EuC/sub 2/O/sub 4/ + 2CO/sub 2/. The reasons for some conflicting differential thermal analysis curves of the rare earth oxalates obtained by others are explained. The europium/sup (II)/ oxalate, EuC/sub 2/O/sub 4/. 1.7H/ sub 2/O, was prepared. (auth)

A New Field Kit for Bullet Hole Identification

The identification of bullet marks and holes is very often essential in criminal cases. The common methods for the determination of trace metals around bullet holes are used in the laboratory and not at the scene of the crime. The application of atomic absorption spectrophotometry and the spot test technique for the determination of lead and copper is reported. Data obtained by test firing a variety of weapons, indicated that the spot test technique can be adapted successfully for the identification of bullet holes. Subsequently, a new kit was developed that facilitates a simple, reliable, and sensitive method for identifying these holes and other suspected marks at the scene of a crime by nonscientific field personnel.