New Insights on Modern Age Coins by Calibration-Free Laser-Induced Breakdown Spectroscopy Method and Chemometric Approaches

Journal of Applied Spectroscopy - The elemental composition of one- and two-rupee coins issued in different years by the Reserve Bank of India (RBI) was investigated using laser-induced breakdown...     

A modified apparatus for determination of carbon in metals by the low pressure method

The low pressure method of determination of carbon in metals and alloys was modified to include certain new techniques. An isopentane slush bath dispensed with the use of liquid oxygen and the usual McLeod gauge was replaced by a differential oil manometer, which increased the sensitivity. As little as 5 μg of carbon in CaCO₃-quartz standards could be determined with a coefficient of variation of 16.0% which improved to 3.3% at the 100-μg level. The apparatus was used for the determination of carbon in metals such as uranium, zirconium and iron and in steels and cupronickel alloy.     

Parallel synthesis of PNA-peptide conjugate libraries

An optimized semi-automatic protocol for parallel synthesis of up to 96 peptide nucleic acids (PNA) or PNA-peptide conjugates using Boc-protection strategy has been developed using a robotic system. The approach is illustrated by synthesizing PNA and PNA-peptide libraries varying between 15 and 27 amino acid units. The peptides (NLS (nuclear localization signal) or Tat-peptide) were attached to N-terminus of the PNA. The method was found to be far superior to that based on the SPOT/Fmoc protocol by which PNA oligomers are synthesized on a modified cellulose membrane. On a 0.5 micromole scale the method typically yielded 2 mg product of 90% purity by HPLC/MALDI-TOF analysis. This approach is suitable for screening of a large number of PNA and/or peptide sequences for biochemical and biological studies.     

Synthesis and characterisation of bis(pentafluorophenyl)antimony(V) cations, [(C6F5)2SbL3]

Pentacoordinate complex cations of the general formula [(C₆F₅)₂SbL₃]³⁺ stabilized as solid salts in combination with tetraphenylborate (BPh₄), tetrafluorobroate (BF₄) anions, where L=DMSO, Ph₃AsO, PyO, DMF, α-, β- and γ-picoline have been isolated. The newly formed complexes were characterized by elemental analysis, molar conductance measurements, solid-state IR and and NMR. From these results, a five-fold coordination around antimony was required.     

Effect of the rate of diffusion of ions on the periodic precipitation of silver chromate

The effect of the rate of diffusion on the formation ofLiesegang rings of silver chromate in gelatin and agar agar medium has been studied. The rate of diffusion of silver ions in the agar agar gel is much slower than that in gelatin gel during the formation of rings of silver chromate. If the rate of diffusion of silver ions in agar agar gel is increased, even then rings do not form. The only change brought about by the rate of diffusion is for the distance between the successive rings.

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Zusammenfassung Der Einflu\ der Diffusionsgeschwindigkeit auf die Bildung vonLiesegang-Ringen aus Silberchromat in Gelatine und Agar-Agar wurde untersucht. Die Diffusionsgeschwindigkeit der Silberionen in den Agar-Agar-Gelen ist viel niedriger als in den Gelatinegelen während der Bildung der Ringe von Silberchromat. Wenn die Diffusionsgeschwindigkeit der Silberionen in Agar-Agar-Gelen gesteigert wird, bilden sich schlie\lich überhaupt keine Ringe. Der einzige Einflu\, den die Diffusionsgeschwindigkeit hervorruft, ist also änderung des Abstandes aufeinanderfolgender Ringe.

     

Preparation and reactions of mono-reissert compounds and analogs at the 3,4-position of quinazoline

Quinazoline, acid chlorides, and trimethylsilyl cyanide have been converted to mono-Reissert compounds at the 3,4-position of the quinazoline system. Various reactions of these quinazoline Reissert compounds are reported.     

A simple autonull-type servo-controlled electronic balance for thermogravimetric applications

A simple electronic autonull-type recording balance using a helical quartz spring is described. Deviation from the null position is detected by a pair of photoemissive cells. The error signal generated across the cells as a result of weight change is processed by a servo-system which, in turn, produces an electric current in the balancing coil proportional to the force required to restore the null position. This current, recorded as the potential drop across a standard resistor, is a direct measure of the weight change.The balance has good linear response and can record weight changes up to 150 mg. The performance of the balance was tested in a thermogravimetric set-up, by studying the decomposition in air of the oxalates of copper, nickel and magnesium. The decomposition of nickel oxalate was also studied in flowing hydrogen. The weighing accuracy of the balance, compared against a Mettler model H-15 single-pan balance, was found to be within±1.5%.

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Zusammenfassung Eine einfache elektronische registrierende Quartz-Spiralfeder Kompensationswaage wird beschrieben. Die Abweichung von der Nullposition wird durch zwei Photoemissionszellen angezeigt. Das infolge der Gewichtsänderung durch die Zellen erzeugte Fehlersignal wird durch ein Servosystem empfangen, das seinerseits in der Ausgleichsspirale einen elektrischen Strom erzeugt, der proportional zur für die Wiederherstellung der Null-position benötigten Kraft ist. Dieser Strom, der als Spannungsgefälle in einem Standardwiderstand registriert wird, ist eine direkte Maßzahl der Gewichtsänderung.Die Waage zeigt ein gutes lineares Verhalten und kann Gewichtsänderungen bis zu 150 mg registrieren. Die Leistung der Waage wurde in einer thermogravimetrischen Vorrichtung durch Untersuchungen der Zersetzung der Oxalate von Kupfer, Nickel und Magnesium in Luft geprüft. Die Zersetzung von Nickeloxalat wurde auch in strömendem Stickstoff untersucht. Die Meßgenauigkeit der Waage, vergleichen mit der Einschalenwaage Mettler H-15 wurde im Bereich von±1.5% gefunden.

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Résumé On décrit une balance électronique enregistreuse simple du type auto-zéro, à hélice de quartz. La déviation de la position zéro est décelée par une paire de cellules photoémissives. Le signal de déséquilibre décelé par les photocellules et résultant d'un changement de poids, est reçu par un système asservi qui, à son tour, produit un courant électrique dans la bobine de la balance, proportionnel à la force nécessaire pour rétablir la position zéro. Ce courant, enregistré comme chute de potentiel dans une résistance étalon, est une mesure directe du changement de poids.La balance donne une bonne réponse linéaire et peut enregistrer des changements de poids allant jusqu'à 150 mg. Ses caractéristiques ont été examinées dans un montage thermogravimétrique, en étudiant la décomposition dans l'air des oxalates de cuivre, nickel et magnésium. La décomposition de l'oxalate de nickel a aussi été étudiée sous courant d'hydrogène. L'exactitude de la balance, comparée à celle d'un modèle Mettler monoplateau (type H-15), coïncide à±1.5%.

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, . . , , -, , . , , . 150 . , . . -15 +1.5%.

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The authors wish to express their thanks to Mr. S. P. Sen, Manager. Catalyst Development and Production Department of Fertilizer (Planning and Development) India Limited, for his keen interest and valuable suggestions.     

Liesegang rings of lead iodide Part II

DistinctLiesegang rings of lead iodide in gelatin gel are not formed as the salt forms a very stabilised colloid in gelatin medium. The stability of the colloid has been investigated. This sol is precipitated by potassium iodide and barium nitrate. Well definedLiesegang rings of lead iodide are formed in the gelatin gel in the presence of electrolytic barium nitrate.     

Polymerization initiated by ylide: Polymerization of ethyl methacrylate with the use of 4-picolinium p-chloro phenacylide as initiator

The ylide 4-picolinium, p-chloro phenacylide-initiated thermal polymerization of ethyl methacrylate (EMA) was studied. 4-Picolinium p-chloro phenacylide induces the thermal polymerization of ethyl methacrylate at 65°C. The rate of polymerization (R_p) rose as the initiator concentration increased from 2 × 10^?3 to 4 × 10^?3 M and the initiating exponent was computed as 1.9. The R_p decreased as the concentration of ylide increased from 6 × 10^?2 to 1M. The greater initiator concentration also affected the molecular weight inversely. The polymerization was carried out at different temperatures and the overall activation energy was computed as 4.08 Kcal/mol. Polymerization was inhibited in the presence of hydroquinone as a radical scavenger. Kinetic studies and other data show that the overall polymerization takes place in a radical mechanism. The various kinetic parameters, such as the rate and average degree of polymerization, molecular weight, and energy of activation of the present system, were evaluated.