bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contribution à l'étude de la transformation allotropique du cobalt
Authors: Lanners A. , Breckpot R. 
Published: September 2010

AbstractThe allotropic transformation of cobalt has been followed with a direct reading X‐ray spectrometer. The α→β transition occurs stepwise between 400° and 500° C, each increase in temperature in the given interval giving rise to the practically instantaneous formation of a new amount of β. The reverse transition occurs similarly but over a much wider temperature range and is not complete even far below 0° C.The proportion of β remaining at room temperature is dependent on the density of lattice defects as measured by the broadening of definite α lines. This proportion can be increased to 90% by severe deformation followed by heat treatment, below 500°. Deformation after heat treatment suppresses totally the β phase. Heat treatment of short duration in the 500° ‐ 1480° C region tends to restore the lattice order, decreasing at the same time the proportion of β, retained in the cold, to some 35%.
Analyses inorganiques avec emploi conjugué du polarographe et de la colonne d'échange
Authors: Gierst L. , Dubru L. 
Published: September 2010

AbstractI. Analytical potentialities of the simultaneous use of exchange and polarographic techniques are briefly discussed.II. Isolation of traces of zinc from cadmium may be performed successfully by use of Dowex 50 exchanger and ammonium citrate buffer as eluting agent, under described conditions. The limiting sensitivity of the method is about 0.002 % Zn in Cd. 0.1% of Zn is determined with an accuracy of 2%.
Etude Expérimentale de l'Oxydation Lente III. Influence de l'hydrogène et de l'oxyde d'azote dans l'oxydation de l'ammoniac
Authors: Volders A. , van Tiggelen A. 
Published: September 2010

AbstractOn a étudié la réaction lente dans les mélanges NH3 + O2 + H2 et NH3 + NO. L'énergie d'activation ainsi que l'ordre de ces réactions par rapport aux pressions partielles des constituants ont été déterminés.L'hydrogène accélère fortement la réaction dans les mélanges NH3 + O2 + H2 et on n'a plus observé les deux domaines (réaction lente et rapide) mis en évidence antérieurement pour les mélanges binaires NH3 + O2.Ces deux domaines subsistent par contre dans le cas des mélanges NH3 + NO, mais la cinétique (énergie d'activation et ordre) est complètement modifiée dès qu'on passe d'un domaine à l'autre.Des schéma réactionnels sont proposés.
Méthodes et appareils utilisés au Bureau des Etalons Physico‐Chimiques XIV. Mesure de la constante diélectrique des composés organiques à 20°C.
Authors: Timmermans J. , Piette A. M. , Philippe R. 
Published: September 2010

AbstractLe présent travail a pour but de montrer qu'il est possible à l'aide d'un appareil courant, d'exécuter des mesures relatives de constante diélectrique avec une reproductibilité et une précision suffisantes. Nous décrivons en détail et sur de nombreux exemples, l'appareil, la méthode de mesure et de calcul utilisés et nous discutons les résultats obtenus en les comparant avec ceux de la littérature.
Le comportement diélectrique des solutions diluées de polyélectrolytes
Authors: De Brouckere Lugia , Vos Gilbert 
Published: September 2010

AbstractDielectric constants of aqueous solutions of polyacrylic acid, partially or totally neutralised by sodium hydroxide, and of sodium, lithium and baryum polymethacrylates, were measured at various frequencies, ranging from 10 to 500 kilocycles. Polymer concentration was varied from 0.1 to 10 millimoles of monomer per liter. The degree of polymerisation was varied from circa 300 to 3,500.All dispersion curves had an inflexion point for frequencies of approximately 100 kilocycles, so that the relaxation times were of the order of one microsecond. It was hardly influenced by the degree of neutralisation, by the polymer concentration or by the molecular weight.The dielectric increment, for a given frequency, increased with the degree of neutralisation, rising sharply until α reached 0.5, rather slowly for higher degrees of neutralisation.The dielectric increment was not proportional to the polymer concentration. It was considerably lower for the salt of a divalent cation, baryum, than for the lithium and sodium salts. The increment was slightly larger for the more mobile sodium than for the lithium polymethacrylate. The degree of polymerisation was practically without influence on the dielectric increment.All the observed facts point to an interpretation attributing the dielectric properties of dilute solutions of polyelectrolytes to relaxation phenomenon in the ionic atmospheres surrounding the charges localised along the polyion.
Comportement du cycle benzénique halogéno‐substitué, sous l'impact électronique (II) Influence de l'énergie des électrons ionisants sur les spectres de masse
Authors: Momigny J. 
Published: September 2010

AbstractThe influence of the energy of ionising electrons on the behaviour of monohalogeno‐substituted benzenes, has been studied.In proportion as this energy is decreasing, the stability of the molecular ions is increasing, but the stability still decreases from fluorobenzene to iodobenzene, as in the case of high energy electrons (see article I).The scope of the diagrams representing the abundance of the principal groups of ions is not affected.Finally the rates of the abundances of certain groups of ions for a given substance passes by a minimum as the accelerating potential of the electrons varies; so that there are generally two different values of this potential for which this ratio takes the same value.
Une application de Calcul Statistique à la Cinétique Chimique
Authors: Huyberechts Melle S. , Halleux A. , Kruys P. 
Published: September 2010

AbstractThe statistical method of least squares has been applied to the estimation of energy and entropy of activation when there is available a variable number of experimental values of the kinetic constant, at several temperatures.Furthermore, the method is described, by which the variances of the estimates can be calculated, and significance tests applied to them.
Etude cinétique des réactions de solvolyse II. Solvolyses des chlorures d'α‐méthylallyle et d'α‐phényléthyle
Authors: Wilputte‐Steinert Mme L. , Fierens P. J. C. 
Published: September 2010

AbstractArrhenius parameters have been measured, conductometrically, in the case of several solvolysis reactions of α‐methylallyl‐ and α‐phenylethyl chlorides.The conductometric method has been extended to kinetic measurements in pure water or in dioxane‐water mixtures, rich in water, and relevant modifications are described.
Contribution à l'étude de l'hydratation des silicates de calcium purs
Authors: van Bemst A. 
Published: September 2010

AbstractRecent experimental results relative to the system CaO‐SiO2‐H2O at ordinary temperature have been applied to the study of the reactions occuring during the hydration of tricalcium and dicalcium silicate.The first part of this work deals with the study of the pure calcium silicate hydrates I and II, i.e. 0,8‐1,5 CaO.SiO2.aq and 1,7‐2,0 CaO.SiO2.aq. They were synthetized by two different new ways and studied by chemical, differential thermal and thermogravimetric analyses, X ray diffraction, electron microscopy and infrared spectrometry.The second part of the work describes the results, based on the same experimental methods, of the study of the reaction between Ca3SiO5, ß and γ Ca2SiO4and various amounts of pure water or lime‐water, at temperatures between 4° and 60°C, after different periods of hydration.The method of determining the composition of the ternary CaO‐SiO2‐H2O phase in samples of partially hydrated silicate is indicated.The rate of hydrolysis of Ca3SiO5increases with decreasing amount of water used for its hydration. The hydraulic properties of tricalcium silicate are enhanced in the conditions of hydrating cement; calcium silicate hydrate II and Ca(OH)2are formed. The mechanism of formation of calcium silicate hydrates I and II from Ca3SiO5is different. Hydrate I is the only one which forms through the liquid phase.
Sédimentation et viscosité de l'acide désoxyribonucléique
Authors: Oth A. 
Published: September 2010

AbstractOn présente une série de mesures de viscosité et de sédimentation faites sur un échantillon d'A.D.N. très polymérisé ainsi que les dimensions et les poids moléculaires que l'on peut en déduire suivant les modèles classiques.
Dosage de l'hydrogène radioactif
Authors: Verly W. G. , Bricteux‐Grégoire S. , Koch G. , Espreux G. 
Published: September 2010

AbstractTritiated hydrogen generated from tritium labelled compounds is introduced into a 100 cm3 ionisation chamber and the filling is completed to atmospheric pressure with ordinary hydrogen; a 300 volts potential difference is established between the electrodes and the ionisation current is determined with a vibrating reed electrometer by the rate of drift method.This set up is able to detect 1 desintegration per second and reduces the background to a value equivalent to the current generated by 2 desintegrations per second, When the activity is above 15 desintegrations per second, the standard deviation on its measurement does not exceed 2 %.
A Theory of Chromatography Based on the Theory of Counter‐Current Distribution
Authors: Verzele M. , Alderweireldt F. 
Published: September 2010

AbstractEn se basant sur la séparation par chromatographie de partage du “complexe des humulones” (sur gel de silice tamponné à pH 9,0 avec l'isooctane comme éluant) les auteurs montrent qu'il est possible d'appliquer la théorie de la “counter‐current distribution” à la chromatographie. La hauteur équivalente à un plateau théorique d'une colonne chromatographique (HETP), notion introduite par Martin et Synge, est équivalente è une cellule d'un train extracteur. Des méthodes pour trouver le coefficient de partage chromatographique (K) et le nombre de HETP's d'une colonne (n) sont données. Les valeurs de K et n étant connues, il est possible, tout comme en C.C.D. de calculer d'avance la courbe chromatographique. Les résultats pratiques de la chromatographie du “complexe des humulones” concordent avec les prévisions théoriques.
Interactions de protéines et d'ions en solution II.‐Energie d'association de la sérumalbumine et d'anions organiques
Authors: Fredericq EugÉNe 
Published: September 2010

AbstractThe binding of picrate, tropeolin, flavianate, naphthol orange, indigo di‐, tri‐and tetrasulphonate anions by serum albumin at pH 4.7 and 3.5 was determined by dialysis at 25°. It is shown that the experimental curves cannot be interpreted by the Scatchard equation and the Debye‐Hückel theory. The charge effect is always much lower than that predicted by the theory. It is proposed to include in the binding equation a term for the Van der Waals energy of interaction. By a consideration of experimental affinities of association, it is possible to estimate the contributions of different energies: electrostatic interactions of charged groups (3,500‐4,500 cal.) and Van der Waals energy increment provided by —CH2—(350 cal.), benzene (1000 cal.) and naphthalene (2,500 cal.) rings. The effect of substituents in the aromatic nuclei is also explained by the consideration of Van der Waals energy and hydrogen bonds.Association constants of anions and serumalbumin or insulin are determined in mixed solvents at pH 3.5 and 6.6. In all cases the association constants strongly weaken in 20% dioxane and practically vanish in 40% dioxane. These facts are in agreement with the hypothesis that electrostatic interactions are greatly exceeded by Van der Waals forces arising between proteins, large anions and solvent molecules.
Synthèse d'acides oxy‐2, isophtaliques substitués
Authors: Hanson G. A. 
Published: September 2010

AbstractL'auteur décrit 1°) la préparation du phényl‐4, anisyl‐6, oxy‐2, isophtalate d'éthyle à partir a) de la benzal p.méthoxyacétophénone, b) de l'anisalacétophénone, par condensation avec l'acétone dicarboxylate d'éthyle; 2°) la préparation de l'acide phényl‐4, o.méthoxyphényl‐6, oxy‐2, isophtalique à partir de l'o.méthoxy benzalacétophénone et de l'acétone dicarboxylate d'éthyle.
Etude expérimentale de l'oxydation lente IV. —Réaction entre l'ammoniac et l'oxyde nitreux
Authors: Volders A. , van Tiggelen A. 
Published: September 2010

AbstractLes réactions NH3 + N2O (avec ou sans NO), N2O + H2 et NO + H2 ont été étudiées.Dans chaque cas on a déterminé l'énergie d'activation ainsi que l'ordre des réactions par rapport à chacun des constituants et par rapport à la pression totale.Les résultats ont été comparés à ceux obtenus antérieurement pour les systémes NH3 + O2, NH3 + O2 + H2 et NH3 + NO.
Effet stérique dans la réaction de l'iodure de potassium sur les α‐chlorocétones
Authors: Fierens P. J. G. 
Published: September 2010

AbstractThe Arrhenius parameters for the reaction of potassium iodide on the α‐chloroketones CH3—CO—CHCl—R (R=Me, Et, iso‐Pr or t.Bu), in anhydrous acetone, have been measured.The differences of reactivity are explained by a steric effect the order of magnitude of which is shown to be analogous to that already observed in SN2 reactions on aliphatic halides R—CH2X.
Echange hétérogène entre le CH3Br et le Br80 (18 mn) issu de Transition Isomérique
Authors: Coekelbergs R. , Gosselain P. A. , Van Venne M. J. Der 
Published: September 2010

AbstractExperiments conducted in Pyrex bulbs and with aluminium and gold coatings have shown that Br80 (18 mn) generated from gaseous CH3Br80 (4,5 h) by isomeric transition, undergoes an heterogeneous exchange reaction with methyl bromide, the importance of which depends on temperature and nature of the wall, and resulting in the appearance of gaseous CH3Br80 (18 mn).A reaction scheme, involving a chemisorbed Br80 (18 mn) and a physically adsorbed CH3Br gives a rate ν = γ p / 1 + α p · nBp is the Br80 (18 mn) adsorbed at the wall, which agrees with the experimental facts between 22°5 and 111°C. In that case, the heat of adsorption of CH3Br on Pyrex would be 5 Kcal, and the activation energy of the exchange process 16 Kcal.
Species differences in Ribonucleases
Authors: Craddock Valda M. , Dalgliesh C. E. 
Published: September 2010

AbstractSpecies differences are shown to exist between various mammalian pancreatic ribonucleases. Rat and beef ribonucleases are readily separable on partition chromatography in a cellosolve‐ammonium sulphate system. This separation is not affected by prior treatment with reducing agents. Rat and beef ribonucleases also behave differently on ion‐exchange chromatography, and on paper electrophoresis under certain conditions of pH.
Untersuchungen über ein blutzuckersenkendes pflanzliches Peptid
Authors: Holt C. V. , Leppla W. 
Published: September 2010

AbstractAqueous extracts from unripe fruits of Blighia sapida contain two ninhydrinpositive substances strongly active in lowering the blood sugar.The active substances are absorbed on columns of Dowex 50 together with inactive ninhydrinpositive material. By repeated extraction of the eluate with a n‐BuOH‐acetic acid mixture an active fraction is obtained. Counter current distribution of this material leads to the isolation of the two active compounds. One of them crystallizes to give a peptide Hypoglycin A. The second substance, Hypoglycin B, isolated in a smaller quantity, was not yet obtained in crystalline form.After acid hydrolysis of Hypoglycin A two‐dimensional paper chromatograms show a number of ninhydrinpositive spots which have not yet been identified with known amino acids. A yellow spot not identical with proline or hydroxyproline is observed.Hypoglycin A is letal in a dose of 4‐5 mg/100 g rat. The animals exhibit a deep hypoglycemia, loss of liver glycogen and a contraction of the left ventricle of the heart. The blood sugar lowering activity of Hypoglycin A is also shown in adrenalectomized and alloxandiabetic rats. The glycosuria of alloxandiabetic rats is markedly reduced under repeated oral administration of one tenth of the letal dose. Neither the glycogen content of the rat diaphragm is significantly influenced by Hypoglycin A in vitro nor an activation of the glycogenolysis of rat liver slices is effected by Hypoglycin A in vitro.The alpha‐cells of the islets of Langerhans show no signs of destruction in animals which died from letal doses of Hypoglycin A.The results and a hypothesis of a possible mechanism of the biological action of Hypoglycin A are discussed.
Some Chemical and Physical Properties of Antidiabetic, an Oral Insulin
Authors: Roberts Richard G. 
Published: September 2010

AbstractThe preparation of a hemin‐insulin‐choline chloride complex has been described. Some of the physical and chemical properties of this preparation are given. This complex was found to have prolonged insulin activity over that of crystalline insulin and also to have activity when administered orally. The hypoglycemic activity of both insulin and Antidiabetic was completely destroyed after treatment in liquid ammonia under pressure at room temperature.
Recent Studies on Sialic Acids
Authors: Werner I. , Blix G. 
Published: September 2010

AbstractFour types of sialic acids have so far been isolated, from cattle, sheep, pig and horse material respectively. They are chemically very closely related and seem to differ in respect of substitutional groups only.The constitution of the substances is still unknown. Some characteristic properties and reactions of the acids are described and the constitutional possibilities are discussed.The relationship of the sialic acids to the neuraminic acid described by Klenk is discussed. It seems highly probable that the methoxy‐neuraminic acid and the different sialic acids are all derivatives of the same basic substance.
Étude radiocristallographique de l'hétérocycle γ‐pyrone I. Structure moléculaire et cristalline de la diméthyl‐2‐6 γ‐thiopyrone
Authors: Toussaint J. 
Published: September 2010

AbstractThe crystal structure of dimethyl‐2‐6 γ‐thiopyrone has been determined by means of electron density projections on the (001) and (100) planes.Bond lengths of the pyrone ring are interpreted in terms of a resonance structure and hence values are deduced for the weights of the forms contributing to the electronic structure of the molecule.
Les spectres Raman de quelques dérivés organiques de l'aluminium et de l'indium
Authors: van Der Kelen G. P. , Herman M. A. 
Published: September 2010

AbstractThe dimethylaluminiumhalogenides [(CH3)2AlX]2 (X = Cl, Br, I) and the monomethylaluminiumhalogenides [CH3AlX2]2 (X = Cl, Br) have been studied in the liquid state by Ramanspectrography. For [(CH3)2AlCl]2 and [CH3AlCl2]2 depolarization factor measurements are reported. For both series of compounds the results agree best with a dimeric structure of symmetry C2v and D2h. Dimerization occurs by formation of a ring comprising two aluminium atoms and two methylgroups.The valence distribution around the aluminium atom with coordination number four is supposed to be tetraedric.These results do not agree with previous measurements of electron‐diffraction on the vapors of dimethylaluminiumchloride and bromide. They agree best with the Ramanspectroscopic studies of aluminiumtrimethyl and of the aluminiumhalogenides.Indiumtrimethyl has also been studied in the liquid and the solid state by Ramanspectrography. The results show, as was expected, that In(CH3)3, is monomeric in both phases and possesses a pyramidal structure of the NH3 type.
The chemistry of the Δ2‐Dihydro‐azoles Part. II. A new method for the preparation of Δ2‐thiazolines
Authors: Nys J. , Libeer J. 
Published: September 2010

AbstractOn décrit une nouvelle méthode de synthèse de Δ2‐thiazolines, basée sur l'ouverture du noyau des Δ2‐oxazolines correspondantes sous l'action de l'acide thiobenzoïque.Plusieurs bases 2‐méthyl‐thiazoliniques non encore décrites dans la littérature et portant en position 4 un ou deux groupements hydroxy‐ ou acétoxyméthyle furent obtenues de cette manière. Après quaternation, elles furent utilisées dans la synthèse de diverses cyanines triméthiniques dont les caractéristiques optiques sont mentionnées et discutées.
Synthèse d'acides 2‐Oxyisophtaliques substitués
Authors: Hanson G. A. 
Published: September 2010

AbstractL'auteur décrit 1°) la préparation de l'acide 4‐phényl, 6‐anisyl, 2‐oxyisophtalique à partir de l'ester éthylique correspondant, 2°) la préparation de l'acide 4,6‐dianisyl, 2‐oxyisophtalique, à partir de l'anisal p.méthoxyacétophénone et de l'acétone dicarboxylate d'éthyle.
The influence of hydrogen on carbon monoxide Oxygen flames
Authors: Slootmaekers P. J. , van Tiggelen A. 
Published: September 2010

AbstractLa vitesse de propagation de la flamme dans les mélanges d'oxyde de carbone et d'oxygène augmente très rapidement lorsqu'on remplace progressivement CO par H2.Par l'étude systématique de cette vitesse à dilution croissante par l'azote de séries de mélanges à rapport H2/CO fixe, on montre que la réaction de ramification des chaînes dans le CO pur est remplacée en présence d'hydrogène par celle qui vaut pour H2 pur. l'énergie d'activation apparente de la ramification varie ainsi de 22 kcal (CO pur) à 18 kcal (H2 pur) tandis que l'ordre apparent de la réaction de ramification passe de 2 à 3.
Contribution à l'étude des éthers monoalcoylés des (poly) éthylène glycols I. Synthéses, constantes physiques et spectres infra‐rouges
Authors: Chakhovskoy N. , Martin R. H. , van Nechel R. 
Published: September 2010

AbstractThe following eighteen (poly)ethylene glycol monoethers have been prepared according to one or the other of the schemes II, IV, V, VI outlined in table I :RO(CH2CH2O)nH R = normal butyl: n = 1;R = normal amyl: n = X and 2; R = normal hexyl:n = 1, 2, 3 and 4; R = normal octyl: n = 1, 2, 3, 4, 5 and 6; R = normal dodecyl: n = 1, 2, 3, 4 and 5.The synthesis of tetraethylene glycol monohexyl ether was achieved by condensing the paratoluene sulfonate of diethylene glycol monohexyl ether with the monosodio derivative of diethylene glycol. As far as we are aware, this type of reaction has never been used before to prepare compounds of this class.The ethers have been purified, as well as possible, by fractional distillation under reduced pressure. The following properties of these compounds were determined: b.p. (°C), m.p. (°C), density (d), refractive index (n29: Hα, D, Hβ, H, Hg'), dispersion of the refractive indices as a function of 1/λ2, molecular refraction, static superficial tension (T. S. 20°C), parachor, elementary analysis (C and H), functional analysis (OH) and infra‐red spectra.The results are summarised in tables II to V.
Hybridation et réactivité V. Solvolyse, par l'acide formique aqueux des chlorures d'allyle et de propargyle
Authors: Fierens P. J. C. , Verschelden P. 
Published: September 2010

AbstractThe solvolysis of allyl and propargyl chlorides have been carried out in the mixture: formic acid (93,6%) ‐ water (6,4%).The relative rates are interpreted in terms of a previously published qualitative general treatment (P. J. C. Fierens, J. Jaminet et P. Kruys, Bull. Soc. Chim. Belges 64, 557 (1955)) based on the competition between two main factors: inductive and mesomeric effects.
Étude cinétique des réactions de solvolyse V. Solvolyses des para‐chlorométhylanisole et para‐chlorométhyltoluène
Authors: Adam‐Briers Mme M. , Bivort P. , Fierens P. J. C. 
Published: September 2010

AbstractThe solvolysis of parachloromethylanisol and parachloromethyltoluene has been studied in several solvents. The Arrhenius parameters have been determined.The results, which are discussed in the light of the Winstein‐Grunwald linear relationship, seem to indicate that these solvolysis are if not, at least not far from the SNI limit.
La sélénosemicarbazide et ses dérivés I. Isomérisation du sélénocyanate d'hydrazine en présence de dérivés carbonylés
Authors: Huls R. , Renson M. 
Published: September 2010

AbstractNous étudions la préparation de la sélénosemicarbazide et des sélénosemicarbazones à partir de l'isomérisation du sélénocyanate d'hydrazine. Nous montrons que la présence d'un dérivé carbonylé est essentielle à cette transformation et nous proposons un mécanisme de réaction.