Reaction of mercury(II) and xylenol orange-I Effect of the buffering media

The influence of the buffering medium on the reaction of Hg(II) with Xylenol Orange has been studied. Amine-type compounds are complexed by Hg(II)/Xylenol Orange with a sharp hyperchromic effect on the reagent itself, at 590 nm, but complex formation of Hg(II)/Xylenol Orange in non-amine-type buffer, such as citric acid-phosphate, gives a hypochromic effect on Xylenol Orange at 580 nm. Hg(II) is determined at pH 7.5 in two ranges of concentration, 2-9 ppm in citrate buffer, measured at 580 nm ( = 2.50 x 10(4)), and 6-11 ppm in hexamine buffer, at 590 nm ( = 4.18 x 10(4)).     

ON THE LUMINESCENCE OF L-TRYPTOPHANE AND l-TYROSINE IN AQUEOUS SOLUTION AT 77dK INDUCED BY X-RAYS AND U.V.-LIGHT

Abstract— The lumincscence arising from L-tryptophane and L-tyrosine in aqueous solutions at 77K during irradiation with u.v.-light and with X-rays has been studied. The spectra obtained with the two types of radiation were largely similar, differing only in that the yields of phosphorescence relative to fluorescence were considerably enhanced in the case of X-irradiation. The decay times observed for the exponentially decaying phosphorescence, being 6.6 sec and 2.7 sec for tryptophane and tyrosine respectively, were the same for both kinds of irradiation. The G-value of the X-ray induced luminescence was about 10 for both tryptophane and tyrosine. Thus, about 30 per cent of the total energy absorbed from X-rays in these compounds was re-emitted as light.
It was concluded that the X-ray induced fluorescence and phosphorescence originate from the same levels as does the luminescence caused by u.v.-light, i.e. the lowest excited singlet and the lowest triplet level of the aromatic structure of these compounds. In the case of X-irradiation the enhanced ratios between the yields of phosphorescence and fluorescence indicated that some process other than excitation directly from the ground state contributed considerably to the luminescence yields. Assuming this process to be a recombination between the ionized molecule and its electron, it was calculated that the contribution to the luminescence yield from excitations directly from the ground state relative to that from ionizations, was negligible for both compounds.     

Wellenmechanische Absolutrechnungen an Molekülen und Atomsystemen mit der SCF?MO?LC(LCGO) Methode. IV. Das Äthylen (C2H4)

The C₂H₄ was investigated ab initio for the equilibrium distance of the centers, taking all 16 electrons into account, using the Allgemeines Programmsystem/SCF ? MO ? LC (LCGO ) Methode. A total energy of ?76.77 a.u. and an ionization energy of 10.55 eV were found.     

Untersuchungen an oxidischen Katalysatoren. XXIX. Spektroskopische und katalytische Untersuchungen an Ni2+-, Co2+-, Cr3+- und Cu2+-ausgetauschten Mordeniten

Studies on Oxide Catalysts. XXIX. Spectroscopic and Catalytic Investigations on Ni²⁺-, Co²⁺-, Cr³⁺-, and Cu²⁺-exchanged Mordenites NiNaM, CoNaM, CrNaM und CuNaM (M = Mordenite) have been characterized by UV-VIS, EPR and i.r. spectroscopy and the results were compared with the catalytic activity and the activity-time-dependence in the cracking of n-octane and with the shape selectivity in the cracking of a n-octane and isooctane mixture. Water molecules acting as ligands of the exchanged cations are able to dissociate yielding Brönsted acidity. Brönsted sites may be regarded as catalytic active centers in the cracking reaction. Unreduced transition metal cations facilitate the “coking” of the mordenite. The unreduced chromium and cobalt cations for which a position within the main channel is expected, affect the diffusion of the branched paraffin molecule thus increasing shape selectivity.     

Gibberellin metabolites from ent-kaura-2,16-dien-19-ol and its succinate in Gibberella fujikuroi

Exposure of ent-kaura-2,16-dien-19-ol (1) or its succinate (2) to resuspended mycelia of G. fujikuroi has produced a complex mixture of acids which after methylation gave the esters of two C₁₉ (24) and (30) and five C₂₀ gibberellins (4, 11, 20, 32 and 33). The triester (32) and the lactone ester (24) have been prepared before from the esters of gibberellin A₁₃ (8) and gibberellin A₄ (26) respectively. The structures of the other metabolites were assigned on spectroscopic data and by chemical transformations. Thus the lactone diester (4) has been converted to the known keto triester (6). The epoxide (11) has been related to gibberellin A₁₄ (14) and the aldehyde (33) has been related to gibberellin A₁₃ trimethyl ester (8) by way of the triol (34). Selective de-epoxidation of the 16,17-epoxy function in diepoxides has provided a route from the dienes (20 and 24) to the epoxides (11 and 30) respectively, but not from the ester of gibberellin A₅ (23) to that of gibberellin A₆ (29). On the other hand the latter can be obtained by epoxidation of gibberellin A₅ methyl ester trifluoroacetate. Backfeeding experiments carried out with the epoxy diacid (12), the diene diacid (21) and the derived diol (39) indicate pathways connecting the various metabolites. The natural gibberellins A₅ and A₆ were shown to be formed in some of the backfeeding experiments.     

Étude du dihydrate de l'acide chlorhydrique par spectroscopie infrarouge et raman: Spectres de vibration de l'ion H5O

An infrared and Raman study of crystalline hydrochloric acid dihydrate is made between 50 and 4000 cm⁻¹. This confirms the occurrence of the diaquohydrogen ion and allows the assignment of its fundamental vibrations. A comparison with the known spectra of H₅O₂⁺ salts with different anions shows that the formation of “external” hydrogen bonds perturbs the central short hydrogen bond vibrations.     

Polymerization of pyromellitic dianhydride with 3,3′-diaminobenzidine in aprotic solvents I. Reaction variables

The solution polymerization of pyromellitic dianhydride with 3,3′-diaminobenzidine to form poly(amide acid amine) was investigated under a variety of reaction conditions. Polymer viscosity and gel formation were highly affected by changes in the order of monomer addition, the type of process (powder or solution), monomer concentration, monomer stoichiometry, and type of solvent. Minor effects were noted with changes in polymerization temperature and the presence of small amounts of water. A limiting intrinsic viscosity of 1.2–1.5 dl/g was observed, regardless of polymerization conditions. The polymerization had a strong tendency to gel at high concentrations and when monomer molar ratios approached 1:1. The conditions which retarded or promoted the formation of macrogel were well-defined, and macrogel but not microgel could be prevented. The polymerization was conducted successfully only in aprotic solvents. No imidazopyrrol-one units were detected in polymer made in polyphosphoric acid at elevated temperatures.     

RECOVERY OF HAEMOPHILUS INFLUENZAE FROM ULTRAVIOLET AND X-RAY DAMAGE

Abstract— Results of experiments on reactivation of ultraviolet (u.v.)-irradiated Haemophilus influenzae and cellular reactivation of u.v.-damaged transforming deoxyribonucleic acid (DNA) and bacteriophage are reported. Liquid-holding recovery (LHR) is small for the u.v.-sensitive mutant BC100 which, relative to the wild type, also has greatly reduced host-cell reactivation (HCR) of u.v.-inactivated phage, and competent cultures show reduced competent cell reactivation (CCR) of u.v.-inactivated transforming DNA. BC100 cells can be transformed with DNA isolated from the wild type strain Rd to a u.v. resistance similar to that of Rd, and irradiation of the DNA reduces the transformation frequency for this marker (uvr). The u.v.-resistant mutant BC200 displays very little LHR under the usual conditions where reactivation occurs after plating. The colony-forming ability (cfa) of irradiated BC200 is greater than that of Rd, but HCR and CCR are the same on this mutant as on the wild type. The major difference between Rd and BC200 is the enhanced u.v. survival of cfa of the latter. It was determined that this difference reflects cell lysis of irradiated Rd and lack of lysis in BC200 cultures. That lysis is closely correlated with damage to the bacterial chromosome is suggested by the finding that the lytic response of Rd (as determined turbidimetrically) can be negated by the liquid-holding procedure, but lysis of BC100 (which lacks comparable DNA-repair ability) can be only partially inhibited by this procedure. LHR occurs when post-plating dark recovery is incomplete, is temperature-sensitive, and occurs unimpeded when post-u.v. protein synthesis is inhibited by chloramphenicol. It is suggested that enzymatically catalyzed reactivation of DNA occurs or is initiated during liquid-holding of u.v.-irradiated H. influenzae Rd and that the necessary enzyme(s) exists prior to appearance of u.v. lesions in the DNA. Results are reported for X-ray inactivation of transforming DNA as assayed on BC100, Rd and BC200 and of the cfa of the three strains.     

Zur Bestimmung von β-Aminocrotonsäureester nach Migration in Lebensmittel

β-Aminocrotonic esters are of great importance as stabilizers for the production of clearly transparent food packaging of PVC. For the purpose of studying the migration into foods a thin-layer Chromatographic and a polarographic method were elaborated. The TLC method consists of the visual comparison of the intensity of the spots after treatment with Fast Blue B salt. The polarographic determination is carried out after nitrosation of the stabilizer. By the TLC method 10^?7 g of ester per spot are still detectable; the concentration which is still determinable by cathode-ray polarography is 5×10^?7 g of ester and by conventional d.c. polarography 5×10^?6g of ester per ml of final solution. After extraction with acetonitrile traces of the stabilizer which are migrated into edible oil are still determinable down to 2 ppm by the methods described.