Alkali Cyanides Research Articles

Density-functional theory for the solid alkali cyanides

Structural properties of the solid alkali cyanides were studied with a recently reported ab initio theory based on the Gordon–Kim electron gas model. The low temperature crystal structures of LiCN, NaCN, KCN, RbCN, and CsCN were examined. The average error in lattice parameters is 2.6% and in lattice dissociation energy 1.7%. For the NaCN and KCN systems, the energy differences between the ferroelectric and antiferroelectric structures were examined and the antiferroelectric structure was found to be more stable at zero temperature by about 0.5–0.8 kcal/mol. The high pressure phases of KCN were studied and the phase diagram partially mapped out at 0 K. The crystal structure of RbCN at low temperatures was studied, and the orthorhombic Pmmn structure found to be more stable than the monoclinic Aa structure. The heat of formation of RbCN was calculated at 0 K to be about 31.4±7 kcal/mol. The cyanide electron density was found to shift from the C atom towards the N atom in all crystals studied, when the free space CN− ion is incorporated into a crystal.

Theory of elastic and phonon softening in ionic molecular solids. Application to alkali cyanides

We have carried out a theoretical study of the effect of coupling between rotational and translational degrees of freedom first proposed by Michel and Naudts on the elastic constants and phonon frequencies of ionic molecular solids. We have applied our theory to the high-temperature plastic phase of alkali cyanides NaCN, KCN, and RbCN. We find that the competition between short-range repulsion and the interaction of the electric quadrupole moment of the C${\mathrm{N}}^{\ensuremath{-}}$ ion with the fluctuating electric field gradient strongly influences the elastic softening and ferroelastic instabilities in these systems. The effect of direct intermolecular interaction and anharmonicity is found to be significant in some cases. The ferroelastic transition temperatures for the above three compounds are found to be 337.5, 190, and 179 K which compare favorably with the experimental values 255.4, 156, and 130 K if we note the mean-field nature of our theory. Within our model we can understand the qualitative differences between the cyanides and the superoxides, a similar class of compounds showing drastically different ferroelastic behavior. Our calculations provide a microscopic justification for the use of certain phenomenological parameters by Strauch et al. in their calculation of phonon frequencies in NaCN and KCN at 300 K.

Elastic Softening and Ferroelastic Instabilities in Alkali Cyanides and Superoxides

It is shown that the competition between short-range repulsion and the interaction between quadrupole moment and fluctuating field gradient strongly influences the elastic softening and ferroelastic instabilities of ionic molecular solids. This theory is applied to explain the ferroelastic properties of alkali cyanides and superoxides.

Spectroscopic investigations on molecules and molecular ions in crystals

A review is given of recent developments in the field of small molecules in crystals. Especially temperature effects are discussed, including the coupling of tunnel states with the lattice and of optical phonons with reorientation modes. The reorientation processes in alkali cyanides, NaOH and NaNO 2 are considered in some detail. A few results concerning the plastic state of molecular crystals are reported.

On the phase transition in alkali cyanides

The phase transition in alkali cyanides is studied starting from a Hamiltonian containing a bilinear coupling term between translational and rotational degrees of freedom, thus leading to an effective rotational interaction. It is shown that the problem can be reformulated in terms of elasticity theory and the effective rotational interaction then becomes an interaction between elastic dipoles. It is demonstrated that the phase transition is of first order. The long range nature of the elastic dipole forces which would lead to a shape dependence of the system for monodomain samples is responsible for the breakup of the ordered phase into domains.

Laser excited luminescence and optical absorption studies of interacting tetracyanoplatinate ions in crystals, pellets, and frozen aqueous solutions

The optical properties of interacting tetracyanoplatinate(II) ions in different environments have been studied by laser excited luminescence, optical absorption, and magnetic circular dichroism. We have examined Pt(CN)4 -2 ion interactions in mixed crystals of alkali halides and alkali cyanides, pure single crystals of the barium and potassium salts, pellets, and in frozen aqueous solutions of different concentrations. Luminescence spectra of mixed alkali halide crystals indicate the presence of dimer and Pt(CN)4 -2 cluster entities in the lattice. Site selective spectroscopy has been used to demonstrate the presence of various sites. Pressed KBr pellets of salts of the Pt(CN)4 -2 ion have been found to contain chains of Pt(CN)4 -2 anions. Frozen aqueous solution studies for a range of concentrations of the Pt(CN)4 -2 ion have allowed us to identify the dimer and cluster spectra with time resolved and lifetime measurements. Optical absorption and magnetic circular dichroism spectra have been compared with MO models for the Pt(CN)4 -2 ion in different environments in order to make electronic assignments.

Pressure and temperature derivatives of the elastic constants of cubic K2SnCl6, Ni( NO3) 2·6 NH3, ( NH4) 2SiF6, andMg( BrO3) 2·6 H2O

The temperature and pressure derivatives of the elastic constants of cubic K 2 SnCl 6, Ni( NO 3) 2·6 NH 3, ( NH 4) 2 SiF 6, and Mg( BrO 3) 2·6 H 2 O have been determined by measuring temperature and stress induced shifts of resonance frequencies of thick plates. K 2SnCl 6 exhibits anomalous thermoelastic properties in a wider temperature range above the transition temperature at 262 K. The shear resistance c″ = ( c 11 − c 12)/2 and also c 11 develop a certain softening approaching the transition from higher temperatures. The anomalies are weakly KCN-type-like and are interpreted as originating from a coupling of librational motions of SnCl 6 octahedra with translational modes. Ni( NO 3) 2·6 NH 3, also in its pressure derivatives, shows anomalies fully analogous to those observed in alkali cyanides. ( NH 4) 2 SiF 6 and Mg( BrO 3) 2·6 H 2 O represent properties characteristic for fluorspar type structures. However, the magnitudes of temperature and pressure derivatives exceed those of the fluorspar type considerably.

Molecular excitons in alkali cyanides

The emission bands of X irradiated Alkali Cyanides were measured at 4.2 K. This emission is associated to the radiative recombination of molecular (Frenkel type) excitons, for the first time observed in these ionic molecular crystals. The nature of the emitting state is discussed and identified as a long lived triplet state.

Lattice dynamics of alkali cyanide crystals

The recent microscopic model of Michel and Naudts for the interaction of ionic vibrational displacements and molecular rotational displacements is combined with the lattice dynamical shell model to calculate phonon dispersion curves of KCN and NaCN. Very good agreement with the existing experimental data is obtained. In particular, the upward dispersion of the TA phonon branches, characteristic of the alkali cyanide crystals, is well reproduced.

Recovery of silver from laboratory wastes

We have tried various procedures for the recovery of silver from the wastes from experiments in the courses in quantitative analysis and have settled on cathodic deposition of silver from acyanide solution in a non-partition cell with stainless steel electrodes. All of the equipment needed can be found in most laboratories or can be purchased at little expense. The procedure is unusually good for instruction and projects at the upper class level. Of the older procedures we have used that of Willbanks ( 1 ) many times with success. It is based on converting the various insoluble silver salts collected to silver hydroxide by digesting with sodium hydroxide, collecting the silver hydroxide, decomposing the oxide to silver metal at 5OO0c, and finally melting the silver into a bar. The chemistry is simple and the procedure an enormous improvement over an earlier scheme in which the solid silver residues (chloride, etc.) are mixed with sodium carbonate and heated to 1 0 o 0 O to llOO°C. Our troubles with these procedures curiously came, on two occasions, from breakage of crucibles and consequent damage to the lining and heating elements of the electric muffle. Steed and Hayes (2) improved the older fusion procedure by using potassium carbonate and provided some useful hints on how to improve the yield and protect the furnace. Our feeling is that securing the large clay crucibles, ball-milling the silver residues with the carbonate (as in the Steed and Hayes procedure), and risking the furnace is too much trouble, even with silver at $0.16 per gram (1977). Of course, if the residues are silver and silver oxide only (from organic preparations), dissolution and digestion with nitric acid, evaporation, and crystallization of silver nitrate, as recommended by Garin and Henderson (3), is more straightforward. An older procedure for converting silver chloride to silver nitrate, Meyer (4, by digesting a suspension of the silver chloride in dilute hydrochloric acid with metallic zinc (powder or fine wire) and working up the metallic silver so formed we found simply too cumbersome and expensive; the digestion is time-consuming, and a second digestion of the metallic silver with hydrochloric acid is necessary to remove the excess zinc. Meyer was interested in the recovery of silver from alloys (silver solder, coinage) and recommended precipitation of the chloride to separate the silver from copper, cadmium, and other metals. We chose electrodeposition of the silver from a cyanide solution rather than from an ammonia solution primarily because we feared that silver-ammonia solutions bpa'reless handling might be slopped about, allowed to dry and produce a shock-sensitive explosive residue. Silver can, of course, be deposited very nicely from an ammonia solution (5,6,7), but silver iodide will not dissolve in a solution of ammonia. On the other hand, all silver salts, except for the sulfide, dissolve in solutions of the alkali cyanides, the electrodeposition can be made from a non-partition cell of simple construction, and excellent deposits of large amounts of silver can be obtained (as for example in the fabrication of silver crucibles for analytical work (8 ,9) ) . The chemistry involved is

Abnormal Undercutting in Etched Cr/Au Films

The etching of gold films deposited on chromium adhesion layers in iodine solution creates cavities at the base of the films. These cavities or abnormal undercutting are revealed and studied by means of the scanning electron microscope. The abnormal undercutting causes the lifting of gold in the etching of high resolution patterns. The alkali cyanide etching solution creates normal undercutting and its use is recommended. It is suggested that the abnormal undercutting results from the formation of an electrochemical cell in the final stage of the etching process when the chromium layer and the gold layer are simultaneously exposed to the electrolyte. The partial oxidation reaction of gold dissolution at the gold surface is balanced by triiodide reduction at the chromium surface as well as at the gold surface. The electrochemical cell formation accelerates the etching of gold near the chromium‐gold boundary and causes the formation of cavities. The mechanisms for the normal and abnormal undercutting processes are discussed.

ChemInform Abstract: REDOX EXTRACTIONS FROM MOLTEN ALKALI CYANIDES. PART 2. MECHANISM FOR EXTRACTIONS WITH LIQUID TIN ALLOYS

Chemischer InformationsdienstVolume 9, Issue 3 Article ChemInform Abstract: REDOX EXTRACTIONS FROM MOLTEN ALKALI CYANIDES. PART 2. MECHANISM FOR EXTRACTIONS WITH LIQUID TIN ALLOYS J. G. V. LESSING, J. G. V. LESSINGSearch for more papers by this authorK. F. FOUCHE, K. F. FOUCHESearch for more papers by this authorT. T. RETIEF, T. T. RETIEFSearch for more papers by this author J. G. V. LESSING, J. G. V. LESSINGSearch for more papers by this authorK. F. FOUCHE, K. F. FOUCHESearch for more papers by this authorT. T. RETIEF, T. T. RETIEFSearch for more papers by this author First published: January 17, 1978 https://doi.org/10.1002/chin.197803127Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume9, Issue3January 17, 1978 RelatedInformation

The electronic absorption spectra of the transition elements Rh, Ir, Ni, Pd and Pt in molten cyanide

Electronic absorption spectra were recorded on molten (Na, K)CN solutions containing rhodium, iridium, nickel, palladium and platinum, at temperatures exceeding 500 °C. Only, those complexes which have characteristic bands at energies lower than 340 nm could be identified; alkali cyanide absorbs strongly at higher energies. The low-oxidation state species, Rh(CN) 3− 4 and Rh(O)-cyanide, Ir(CN) 3− 4 and Ir(O)-cyanide complexes are present in the molten salt when the metals are dissolved as III- and I-oxidation state compounds. The complex Pd(I)-cyanide is formed whenPdCl 2 is dissolved in the melt, while Pt(I)-cyanide and Pt(O)-cyanide are formed when K 2PtCl 4 is dissolved in the melt. An Ni(I) complex,Ni 2(CN) 4− 6, was identified in the molten cyanide to which NiCl 2 and Ni sponge had been added. A description also given of the spectroscopic equipment used, as well as of the graphite sample cell with diamond windows.

Neutron diffraction study of the structure and phase transitions of alkali cyanide crystals

The structures of sodium and potassium cyanide have been studied by neutron powder diffraction as a function of temperature between 6 and 300 K. The orientation of the CN ions in the lowest temperature phase has been established, and the mechanism of the order–disorder phase transitions has been elucidated by a careful study of a superlattice line intensity in KCN.

The purification of alkali cyanide melts

The impurities expected to be present in alkali cyanide melts are discussed, and methods for their removal from a (K, Na)CN eutectic melt are then suggested. It was found that room-temperature vacuum-drying, combined with melting of the salt in the presence of silicon powder, gives the best results. The purity of melts is evaluated by infrared spectroscopy on quenched melt samples.

Neutron scattering studies of crystal dynamics and order-disorder phase transitions in alkali cyanides

Abstract The structure, phase transitions and crystal dynamics of KCN and NaCN have been studied by a series of neutron diffraction and inelastic scattering measurements. High resolution powder diffraction results on the three phases of both salts show that the ordered low temperature phase has an “antiferroelectric” orthorhombic structure, based on a primitive orthorhombic unit cell with essentially the same dimensions as the body-centered orthorhombic cell of the intermediate phase. The characteristic superlattice diffraction peak vanishes as the phase transition temperature is approached from below in the manner expected for a continuous order-disorder phase transition. In accord with other workers, we find no evidence of second-order behavior below the orthorhombic-cubic phase transition. Neutron inelastic scattering results are presented for the cubic phase of KCN, including a careful study of the behavior of a soft shear mode down to the cubicorthorhombic phase transition.

Lattice dynamics of ND4I in the NaCl phase (I) at 296°K

Dispersion curves for translational phonons propagating in the high-symmetry directions of sodium-chloridephase N${\mathrm{D}}_{4}$I have been determined at room temperature by coherent inelastic neutron scattering from single crystals. Acoustic phonons were well defined throughout the Brillouin zone. Optic phonons were considerably more difficult to measure because of the low signal-to-background ratio. The observed phonon energies were fitted to a "simple" and a "breathing" shell model with general repulsive short-range forces out to second neighbors. The results of the model fitting lead to conclusions similar to those reached in previous alkali halide studies. Model predictions of crystal properties are generally in good agreement with observation. The best fit model was used as an interpolation formula to calculate the density of states, $g(\ensuremath{\nu})$. The mean-square displacements are in excellent agreement with those derived from the neutron-diffraction results of Seymour and Pryor. The lattice-dynamics results are compared with similar results obtained recently for the NaCl phases of the alkali cyanides.

Extractive Separation and Direct Colorimetric Determination of Cadmium with Thiothenoyltrifluoroacetone

Abstract Thiothenoyltrifluoroacetone (STTA) was used for the quantitative extraction of cadmium at tracer level. Cadmium was extracted completely at pH 6.5-7.5 with 0.001 M STTA in carbon tetrachloride as the yellow colored complex which could be measured colorimetrically at 450 nm. The system adhered to Beer's law in the concentration range of 0.9 to 19 μg/ml. The complex was stable for at least 96 hr. Ten milliliters 0.001 M STTA in carbon tetrachloride was adequate for quantitative extraction of cadmium. The optimum period of equilibration was 10 min. It was possible to effect extractive separation and colorimetric determination of cadmium in the presence of 1 : 200 of alkali, alkaline earths, thallium, germanium, and organic complexing acids. Other ions were tolerated in the ratio ≥ 1 : 20. The method was rendered selective by using sequestering agents, such as citric acid, tartaric acid, or alkali cyanide, or by resorting to selective extraction process with either tributylphosphate or acetylacetone.

Reaction of ε- Caprolactone with Alkali Cyanide

6-Cyanohexanoic acid was prepared by the reaction of e-caprolactone with alkali cyanide in the presence of a certain catalyst.As the catalyst of this reaction, KI, NaI, I2 and NH4I, gave good results. The highest yield of the acid was 65%.e-Caprolactone polymer reacted in the same manner as the monomer, but its cyclic dimer gave the cyano acid in only 35% yield.5-Hexenoic acid and pimelonitrile were obtained as by-products.

Mechanism of the color reaction between m-dinitrobenzene derivatives and alkali cyanide. 3. Reaction products of 2,4-dinitrophenol with potassium cyanide

Mechanism of the color reaction between m-dinitrobenzene derivatives and alkali cyanide. 3. Reaction products of 2,4-dinitrophenol with potassium cyanide