The first results are presented from some experiments aimed to determine the porosity and different capacity to absorb humidity from soil of several pre-hispanic building materials covered with mural painting which are under restoration at present. The main destructive agents are not coming from external weather conditions, but from humidity originated in the soil with a great variety of dissolved salts. In the laboratory small prism shaped samples of the same raw materials utilized in ancient times have been tested and put in contact with a 1& Na2SO4 solution labeled with 22Na during fixed time periods. In this way, counts obtained divided by weight of each sample gives a figure approximately proportional to its porosity or capacity to absorb humidity from soil, making possible to compare the difference of this condition for several materials, and to test the efficiency of the proposed methods to control this problem. One suitable way to achieve it, seems to be the use of one solution of BaAc, plus thio-urea and methyl-methacrylate, in order to form a solid polymer. This method works reasonably well at laboratory level, and even when it has not been tested in the real scale, seems to be cheap and easy enough to slow down the increasing deterioration due to humidity and salts deposits coming from soil. However, even when this polymer is completely insoluble in water, the start of the reaction to form it requires the final addition of hydrogen peroxide, and temperature increase till the boiling point of the reagents, which may be too aggressive for ancient dyes and raw materials. Thus, the use of the so called French gelatin is proposed, and results at laboratory level are considered to chose the material better suitable at real scale with a minimum risk for the material.
Authors:Francisco C. C. Arantes, Antonio C. Moro, Iolanda S. Klein, Cristiana da Silva, Adelino V. G. Netto, Antonio E. Mauro, and Vânia M. Nogueira
chemistry of thiourea (tu) and substituted tu derivatives has attracted attention because of their potential use as reagents for the separation of metal ions [ 5 ] and in biological applications such as their employment as antitumor and antimycobacterial
New zinc acetate based complex compounds (of general formula Zn(CH3COO)2·1−2L·nH2O) containing one or two molecules of urea, thiourea, coffeine and phenazone were prepared namely: Zn(CH3COO)2·2.5H2O, Zn(CH3COO)2·2u·0.5H2O, Zn(CH3COO)2·tu·0.5H2O, Zn(CH3COO)2·2tu, Zn(CH3COO)2·cof·2.5H2O, Zn(CH3COO)2·2cof·3.5H2O, Zn(CH3COO)2·2phen·1.5H2O.
The compounds were characterized by IR spectroscopy, chemical analysis and thermal analysis. Thermal analysis showed that
no changes in crystallographic modifications of the compounds take place during (heating in nitrogen before) the thermal decompositions.
The temperature interval of the stability of the prepared compounds were determined. It was found that the thermal decomposition
of hydrated compounds starts by the release of water molecules. During the thermal decomposition of anhydrous compounds in
nitrogen the release of organic ligands take place followed by the decomposition of the acetate anion. Zinc oxide and metallic
zinc were found as final products of the thermal decomposition of the zinc acetate based complex compounds studied. Carbon
dioxide and acetone were detected in the gaseous products of the decomposition of the compounds if ZnO is formed. Carbon monoxide
and acetaldehyde were detected in the gaseous products of the decomposition, if metallic Zn is formed. It is supposed that
ZnO and Zn resulting from Zn acetate complex compounds here studied, possess different degree of structural disorder. Annealing
takes place by further heating above 600°C.
Authors:P. Aslanidis, K. Chrissafis, and M. Lalia-Kantouri
early reported as 1:1 electrolytes for [Cu(py2SH) 3 ] + NO 3 − [ 16 ] and recently for the isomorphous anhydrous monomeric compounds [Cu(tu) 3 ] + X − (tu = thiourea and X = Cl, Br), while as 1:2 electrolytes for the isomorphous hydrated dimeric
The thermal behaviours of alkylammonium and potassium N-alkylthiocarbamates of general formula (RNH3) (RHNCXY) (where X= Y= S or X= S and Y= 0; R=n-C3H3,i-C3H3,n-C4H9,i-C4H9 orc-C6H11) and K(RHNCOS) (where R=CH3, C2H5,n-C3H7,i-C3H7,n-C4H9,i-C4H9 orc-C6H11) were investigated. The decomposition mechanisms exhibit a similar character for all studied compounds. In the course of thermolysis symmetric dialkylureas and dialkylthioureas, as well as amines, CS2 (or COS) and H2S are formed. The alkylammonium thiocarbamates decompose without any residue, whereas with potassium monothiocarbamates potassium sulfate is left as a residue. For the process of urea and thiourea formation during the first step of decomposition, the activation energies were computed for some compounds.
Authors:M. Amutha, G. Ramasamy, S. P. Meenakshisundaram, and S. C. Mojumdar
Bhagavannarayana , G , Kushwaha , SK , Parthiban , S , Meenakshisundaram , S . The influence of Mn-doping on the nonlinear optical properties and crystalline perfection of tris(thiourea) zinc(II) sulphate crystals: concentration effect . J Cryst Growth