Determination of HCN sampled from gasification product gases by headspace gas chromatography with atomic emission detector

Nitrogen-containing fuels produce hydrogen cyanide when the fuel is gasified. The gas is poisonous and produces nitrogen oxides when it is burned. HCN is usually sampled into alkaline solutions and analysed using an ion selective electrode. The method is tedious and the electrode response is temperature-dependent. Samples are not stable and must be analysed immediately, and they contain ions which are poisonous to the electrode. Therefore a new gas chromatographic method was developed. In this new method HCN is released from the alkaline solutions with sulphuric acid in a headspace sampler and analysed by a gas chromatograph connected to an atomic emission detector. Measurements on carbon emission line 193.1 nm gave the limit of detection 0.05 mg CN^–/l in the solution. The calibration curve was linear to 1000 mg CN^–/l and the correlation was 0.997. The relative standard deviation of the calibration was 1.7% at the concentration of 5 mg CN^–/l and 1.0% at 25 mg CN^–/l. The developed headspace method allows automated analysis and it needs less sample preparations than the ion selective electrode method. This paper also reports the effect of sample preparation and storage time on the stability of the samples.     

Electronic and vibrational signatures of the Au102(p-MBA)44 cluster

Optical absorption of a gold nanocluster of 102 Au atoms protected by 44 para-mercaptobenzoic acid (p-MBA) ligands is measured in the range of 0.05-6.2 eV (mid-IR to UV) by a combination of several techniques for purified samples in solid and solution phases. The results are compared to calculations for a model cluster Au(102)(SMe)(44) based on the time-dependent density functional theory in the linear-response regime and using the known structure of Au(102)(p-MBA)(44). The measured and calculated molar absorption coefficients in the NIR-vis region are comparable, within a factor of 2, in the absolute scale. Several characteristic features are observed in the absorption in the range of 1.5-3.5 eV. The onset of the electronic transitions in the mid-IR region is experimentally observed at 0.45 ± 0.05 eV which compares well with the lowest calculated transition at 0.55 eV. Vibrations in the ligand layer give rise to fingerprint IR features below the onset of low-energy metal-to-metal electronic transitions. Partial exchange of the p-MBA ligand to glutathione does not affect the onset of the electronic transitions, which indicates that the metal core of the cluster is not affected by the ligand exchange. The full spectroscopic characterization of the Au(102)(p-MBA)(44) reported here for the first time gives benchmarks for further studies of manipulation and functionalization of this nanocluster to various applications.     

Cellulose--model films and the fundamental approach

This critical review describes the recent arrival of ultrathin films of cellulose. The methodology of preparation as well as the applications of the films for fundamental research is fully covered. The review places cellulose in a wider scientific context where cellulose research is no longer a field of interest for specialised scientists only. Cellulose and cellulosic materials should interest communities such as biochemists, physical chemists, surface chemists, organic chemists, polymer chemists and also physicists working close the disciplines mentioned. (149 references.).     

Modification of olefin polymerization catalysts. I. Mechanism of the interaction between AIEt3 and silyl ethers

The interaction between AlEt₃ and silyl ethers, Ph_nSi(OMe)_4-n (n = 0–3), was followed by ¹³C- and ²⁹Si-NMR techniques in conditions close to those typical for an olefin polymerization reaction with supported Ziegler–Natta catalysts (A1Et₃:silyl ether ratios from 1 to 10, temperature range 25–75°C). A1Et₃ and silyl ethers form instantaneously at ambient temperature a donor-acceptor complex, which is stable at a 1:1 molar ratio. In the presence of excess A1Et₃ the complex decomposes via a mechanism consisting, in the case of PhSi(OMe)₃, of five consecutive steps: alternating complexation and ether reductions with the formation of alkylated silyl ethers, Ph(Et)_nSi(OMe)_3-n (n = 1,2), and dialkyl-aluminum alkoxides, (Et₂A1OMe₃)_n (n = 2,3). The rate of decomposition was enhanced by the increasing number of methoxy groups present in the silyl ether, heating, or a high A1Et₃:silyl ether ratio. The decomposition was not inhibited by the presence of 1-hexene.     

Separation of caffeine from antipyrine by means of cation exchanger in the ferric iron form

The ion exchange separation method presented in this paper is based upon the ability of antipyrine to form complexes with ferric iron. On passing an aqueous solution of caffeine and aratipyrine through a cation exchanger in the ferric iron form, antipyrine is quantitatively taken up. Caffeine, however, is completely displaced from the column on washing with water at elevated temperature and determined spectrophotometrically in the ultraviolet region. This procedure has been found to be simpler and more precise than others previously used.     

Two queues in tandem

A system consisting of two queues in series, the output of one queue being the input of the other, is described. General distributions are discussed, but the exponential distribution is given particular consideration.     

A non-singular spherically symmetric separable copy of the vacuum in SU(2) Landau gauge

We give a new non-singular spherically symmetric and separable copy of the vacuum in Landau gauge for SU(2) Yang-Mills theories. The solution can be considered as a generalization of Gribov's solution in Coulomb gauge and thus it demonstrates the similarity between vacua in Coulomb and Landau gauges.