Effects Of Changes In Concentration Research Articles

Studies on Direct Synthesis of Acrylonitrile. IX

The effects of change in concentration of NH4C1, CuCl, and HCl in CuC1-NH4C1 catalyst pretreated with HCN on the loss of HCN by evolution, thevelocity of formation of acrylonitrile (AN) and an induction period for formationof AN have been investigated.An increase in concentration of NH4Cl in Newland's catalyst accelerated thevelocity of evolution of HCN and the induction period for formation of AN wasgradually increased. Although the velocity of formation of AN was increasedup to a certain concentration of NH4Cl, it decreased gradually thereafter. A peakfor formation of AN was appeared by the presence of an equimolar mixture of NH4Cl and CuCl after passing through the induction period. Also, NH4Cl in thepresence of CuCN had no direct relation in the synthetic reaction of AN atany stage of reaction.There was no parallelism between the velocity of lossof HCN by evolution and the velocity of formation of AN.An increase in concentration of CuCl caused the loss of HCN by evolutionin an inversely related way and this was inversely relatad to the reaction of NH4Cl. The induction period for AN formation was shortened in such a way asinversely related to the concentration of CuCl, but the velocity of formationof AN was increased up to a certain cencentration of CuCl and became constantthereafter. An increase in concentration of HCl caused an increase in the loss of HCN by evolution and this was accompanied with an increase in the velocity off ormation of AN as well as an increase in induction period for its formationsimilar to that of NH4Cl but it showed no peak in the formation of AN asshown by NH4Cl.

Viscous properties of thixotropic materials

Measurements have been made on the viscous properties of suspensions of titanium dioxide pigments in linseed stand oils. The effects of changes in concentration and temperature have been noted. The viscosity under steady flow conditions cannot be adequately defined by a single coefficient but it is convenient to display the results graphically, plotting shear stress against velocity gradient. It is shown that the shear stress required to maintain any steady velocity gradient has two components, one being independent of temperature and the other proportional to the viscosity of the medium as this changes with temperature. The samples studied took some time to attain steady conditions of flow and the approach to this state, the thixotropic relaxation, occurs in a very complicated way. Two qualitative conclusions could be drawn: that the magnitude and speed of change decreased with increasing values of shear stress, and that the magnitude and speed of change (at the same shear stress) increased with increasing concentration.

Precision viscometry of polyvinyl acetate in toluene

AbstractThe viscosity of dilute solutions of PVA in toluene is investigated as a function of shearing stress in an Ubbelohde precision viscometer which permits determining the efflux time to within 3 × 10−3 sec. Various sources of error in capillary viscometry are discussed. Correction for drainage is made on the basis of a newly developed theory. In a first series of measurements uncorrected values of (t − t0)/t0c are shown to give an anomalous curve when plotted against c. In this series the effect of changes in concentration as a result of adsorption onto the walls of the dilution vessels is studied. The anomaly disappears when corrections are made for various sources of error and for non‐Newtonian behavior in particular (second series). The thickness of the adsorption layer on the wall of the capillary is estimated from results in two viscometers with different bore. A comparison with direct measurements of adsorption on glass beads reveals that the average density of the polymer adsorbed is about 0.17 g./ml. The viscosity at low shearing stress is an even function of the shearing stress. The intrinsic viscosity is markedly dependent on shear rate, its value at high shear rates being about 40% of that of zero shear rate.

Theory of the effect of counterion size upon titration behavior of polycarboxylic acids

AbstractThe effect of the ionic radius of counterions has been introduced into the dissociation theory of polyelectrolytes, using the familiar rod‐like model. Increments in the average dissociation constant pKa and slope n for polyacrylic acid with increasing size of the gegenion have been calculated and compared with data using potassium and some tetraalkylammonium hydroxides. Good agreement is encountered. The effects of changes in concentration of the polyacid and of the presence of neutral salt are also considered.

The effect of changes in concentration of cations on the electrocardiogram of the isolated perfused heart

Action potentials were recorded simultaneously from the cavity and the epicardium of the ventricle of the isolated perfused hearts of the dog and the turtle before and after alteration of the concentrations of the various cations in the perfusate. The major effects of an excess of potassium on the turtle heart were similar to those on the heart of the dog (prolonged QRS interval, shortened S-T interval, broad P waves, and terminally monophasic or diphasic complexes). However, in the turtle heart the atria and sinus venosus were more tolerant than the ventricle to an excess of potassium; both mechanical contraction and electrical activity of the atria persisted after complete ventricular arrest, while in the dog both mechanical and electrical activity of the atria ceased long before that of the ventricles. An increase in the amplitude of the T wave was observed in the dog and turtle hearts under the influence of an excess of potassium; the width of the T wave was increased or remained the same. The addition of extra calcium to a perfusate containing an excess of potassium lessened the delay in intraventricular conduction and further shortened the S-T interval produced by the excess of potassium. Restoration of a low sodium concentration to normal partially reversed the alterations in the electrocardiogram characteristic of an excess of potassium. In the turtle heart a reduction of the sodium concentration in the presence of an excess of potassium enhanced the effects of the latter. Increase of the sodium concentration in the presence of an excess of potassium partially antagonized the effects of the latter. Complete absence of potassium from the perfusate prolonged the P-R interval, prolonged the QRS interval, prolonged the S-T interval, and widened the T waves in the turtle heart. Except for slight or no widening of the QRS complex before atrioventricular dissociation developed, similar changes took place in the dog heart when the perfusate contained no potassium. The electrocardiographic changes in the dog heart were consistent with those found in cases of human beings with hypopotassemia.

THE EFFECT OF CHANGES IN CONCENTRATION OF PANTOTHENATE ON THE WORK OUTPUT OF PERFUSED FROG MUSCLES

ArticleTHE EFFECT OF CHANGES IN CONCENTRATION OF PANTOTHENATE ON THE WORK OUTPUT OF PERFUSED FROG MUSCLESN. W. Shock, and W. H. SebrellN. W. ShockFrom the Division of Physiology, National Institute of Health, Bethesda, Maryland and the Baltimore City Hospitals, Baltimore, Maryland, and W. H. SebrellFrom the Division of Physiology, National Institute of Health, Bethesda, Maryland and the Baltimore City Hospitals, Baltimore, MarylandPublished Online:01 Sep 1944https://doi.org/10.1152/ajplegacy.1944.142.2.274MoreSectionsPDF (702 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited BySerum metabolites associated with feed efficiency in black angus steers27 October 2017 | Metabolomics, Vol. 13, No. 12 More from this issue > Volume 142Issue 2September 1944Pages 274-278 Copyright & PermissionsCopyright © 1944 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1944.142.2.274History Received 3 June 1944 Published online 1 September 1944 Published in print 1 September 1944 Metrics

The Viscosity of Aqueous Solutions of Chlorides, Bromides, and Iodides

Summary1. We have determined the relative viscosity of aqueous solutions of KCl, KBr, KI, HCl, HBr at 0°, 15°, and 25° C.; and at concentrations of 1 mol., 2 mol., and 3 mol. per litre. Also the equivalent conductivity of the same solutions at 0° C.2. The change of viscosity with change of temperature diminishes from Cl-Br-I.3. The effect of concentration on the viscosity depends on the temperature: it may affect the viscosity in opposite directions at different temperatures.4. There are considerable differences in viscosity of chloride, bromide, and iodide, and especially in the effect of changes in concentration and temperature.