Humidity sensitivity of metal ferrite nanoparticles [MFe 2 O 4 , M (II) ¼ Co, Cu, Mg, Ni and Zn] prepared by solid-state reaction of inorganic precursors was studied. The process was convenient, environmentally-friendly, inexpensive and efficient. The spinel structure of the compounds prepared by this method was confirmed by XRD and FT-IR studies. The surface morphology was observed by scanning electron microscopy, and the surface area was analysed by the nitrogen adsorption/desorption study by the Brunauer-Emmett-Teller (BET) method. All the samples were subjected to dc electrical conductivity studies at room temperature. The resistance measurements as a function of relative humidity in the range of 5-98% and the sensitivity factor (S f ¼ R 5% / R 98% ) were calculated. Among all the metal ferrites, zinc ferrite (ZnFe 2 O 4 ) possessed the highest humidity sensitivity factor of 2895 � 85, whereas the other compounds possessed a very low sensitivity factor. The response and recovery times of ZnFe 2 O 4 were 330 and 80 s.

In the title compound, [Co(C4H7N2O2)Cl2(C4H8N2O2)], the CoIII ion has a distorted octa­hedral coordination environment. The equatorial plane consists of four N atoms, two each from the dimethyl­glyoxime and dimethyl­glyoximate ligands, while the two axial positions are occupied by two chloride ions. Strong intra­molecular O—H⋯O hydrogen bonds are observed between the dimethyl­glyoxime and dimethyl­glyoximate ligands. Mol­ecules are linked into a chain running along the [101] direction by O—H⋯O and C—H⋯Cl hydrogen bonds. The chains are cross-linked through inter­molecular C—H⋯Cl hydrogen bonds.

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Iron (11) Reduction of trans-B is( d imet hylg lyoximato) halogenopyr id i neco balt (111) Complexes: Kinetics and Mechanism

In the title complex, [CoCl2(C10H8N2)2]·3H2O, the Co(II) ion is situated on a twofold rotation axis and exhibits a slightly distorted octa­hedral geometry and is chelated by four N atoms of the two bidentate 2,2′-bipyridine ligands and two Cl− ions. The crystal packing is stabilized by hydrogen bonding formed between chloride ions and adjacent water mol­ecules. One of the two independent water molecules in the asymmetric unit is disordered over two sets of sites, each on a twofold rotation axis, in a 0.734 (17):0.269 (17) ratio.