A heterogeneous distribution study with internally formed lead chromate as host and110Ag as guest indicates the existence of a new variety of lead chromate, which forms mixed crystals with silver chromate, and
differs in morphology from the aged variety. It is inferred that the formation of mixed crystals is probably due to breeding
of a morphologically analogous and unstable species by the guest component. By means of study of the homogeneous distribution
coefficient, D, of the system consisting of KFe(SO4)2·12H2O as host and110Ag as guest, the existence of an unknown alum, AgFe(SO4)2·12H2O, in trace amounts has been demonstrated. A distribution study of the system shows that KFe(SO4)2·12H2O forms mixed crystals with110Ag up to 10°C, after which the uptake follows an adsorption pattern. The transition temperature of the guest alum, indicated
by a sharp change in the D values, is found to be 10°C. Application of radioactive tracers in the study of new and unstable
compounds have been stressed.
The RC1 calorimeter revealed itself a suitable instrument to obtain information about safety and mechanisms involved in the reaction between cyclohexanecarboxylic acid (AEB) and oleum. A previous hypothesis about the existence of an unstable intermediate was confirmed and its heat of formation was calculated. The heat of sulphonation related to undesirable by-products production and the heat of protonation of AEB with H2SO4 were also evaluated. Therefore, it was possible to distinguish the reactions involved in the process and, through their thermal behaviour, to determine the limit conditions to avoid the by-products formation.
Authors:Tsuneo Kashiwagi, Fumihiro Amemiya, Toshio Fuchigami, and Mahito Atobe
We have successfully demonstrated that a microflow reactor is extremely useful in controlling reactions involving an unstable o-benzoquinone. As a model reaction, Michael addition reaction between o-benzoquinone generated from electrochemical oxidation of catechol and benzenethiols was employed. This reaction system enables selective oxidation of catechol avoiding the oxidation of benzenethiol, although these oxidation potentials are close to each other. The examination of several reaction conditions indicated that the key features of the method are an effective o-benzoquinone generation and its rapid use for the following reaction without decomposition in a microflow system. In addition, cyclic voltammetry measurements elucidated that catechol concentration and selection of anode material were crucial factors for effective o-quinone generation.
The study of homogeneous distribution coefficients in determining the transition temperatures of isomorphologically analogous
components and in predicting the existences of some new unstable compounds has been carried out in detail with special references
to vitriols of nickel, manganese, zinc, copper and magnesium. In the course of the investigation with NiSO4·7H2O as host and54Mn as guest, the transition temperature of orthorhombic NiSO4·7H2O was shown to be 26.5 °C, and with orthorhombic ZnSO4·7H2O and MgSO4·7H2O as host and copper sulphate as guest, the limits of existences of orthorhombic CuSO4·7H2O and newly predicted CuSO4·6H2O were found to be 13.5° to 44 °C and 44° to 51 °C, respectively. In addition, the transition temperatures of orthorhombic
MnSO4·7H2O (10 °C), stable NiSO4·7H2O (30.5±5 °C) and orthorhombic ZnSO4·7H2O (39 °C) were verified. The new method of approach is very simple, reproducible and easily adaptable.
not forming common chemical compounds or forming unstablecompounds can also be incorporated into the glass network. An example of this are glasses containing oxides and nitrides, oxides and carbides, oxides and fluorides, P 2 O 5 and SiO 2 , TiO 2
Authors:Judit Perjéssy, Ferenc Hegyi, Magdolna Nagy-Gasztonyi, Rita Tömösközi-Farkas, and Zsolt Zalán
h control Fig. 6. Effect of lactic acid fermentation on free radical scavenging capacity in % in sour cherry juice compared to the 0 h control Anthocyanins and flavonols Anthocyanin is the most unstablecompound among natural products that is