<p>Hydroxyapatite (HAp) is a unique material having high adsorption capacity of heavy metals, high ion exchange capacity, high biological compatibility, low water solubility, high stability under reducing and oxidizing conditions, availability and low cost. Hydroxyapatite nanoparticles have been synthesized by Sol-gel method using Calcium nitrate tetrahydrate [Ca(NO₃)₂•4H₂O] and Phosphorus pentaoxide (P₂O₅) as starting reactants. The addition of Phosphorus pentaoxide to Calcium nitrate tetrahydrate was carried out slowly with simultaneous stirring. After addition, solution was aged for 10 minutes for maturation. The precipitate was dried at 80 °C overnight and further heat treated at 550 °C for 2 hours. The dried and calcined particles were characterized by X-ray diffractometry, Fourier transform infra-red spectroscopy and Thermo gravimetric analysis. The particle size and morphology were studied using transmission electron microscopy. TEM examination of the treated powders displayed particles of polygon morphology with dimensions 20-50 nm in length. The FT-IR spectra for sample confirmed the formation of hydroxyapatite.</p>

Low molecular weight polyketones were prepared by the Friedel‐Crafts reaction from p‐cresol, chloroacetylchloride and dichloroalkanes, i. e. dichloromethane and 1,2‐dichloroethane. The polyketones were characterized by IR spectra and vapour pressure osmometry. The thermal properties were studied by thermogravimetry and differential scanning calorimetry. The kinetic parameters for the thermal decomposition reaction were evaluated by the methods of Broido and Doyle. The polyketones were found to be thermally stable up to 200°C. They show antimicrobial properties against bacteria, fungi and yeast.

SUMMARYChlorine-containing polyketones of low molecular weight were synthesized from anisole, chloroacetyl chloride and dichloroalkanes, i. e. dichloromethane and 1,2-dichloroethane, by the Friedel-Crafts reaction using carbon disulfide as solvent. The resins were characterized by IR spectra and vapour pressure osmometry. The thermal properties were studied by thermogravimetry and differential scanning calorimetry. The characteristics of the decomposition reactions were evaluated by the Broido and Doyle methods. All the resins were tested for their microbial activity against bacteria, fungi and yeast. The results show that most of the resins can be used as biocides. ZUSAMMENFASSUNG:Chlorhaltige Polyketone mit niedrigem Molekulargewicht wurden nach FriedelCrafts aus Anisol, Chloracetylchlorid and Dichloralkanen (Dichlormethan, 1,2-Dichlorethan) in Kohlenstoffdisulfid hergestellt. Die Harze wurden mittels IR-Spektroskopie und Dampfdruckosmometrie charakterisiert. Das thermische Verhalten wurde thermogravimetrisch und differentialkalorimetrisch untersucht. Die Zersetzungscharakteristik wurde nach Broido und Doyle ermittelt. Die Priifung der mikrobiellen Aktivitat der Harze gegeniiber Bakterien, Pilzen und Hefen ergab, darj sich die meisten Harze als Biozide verwenden lassen.