residues from the sheet 39 s surface b 20 samples squares of paper about 4 u00d7 4 cm of the average weight of 0 15 g each for a total of 3 g were completely immersed in a glass weighing bottle u00f8100 mm h 50 mm containing 100 ml of an ethereal solution of 2 1 piperidine diazoethane 0 3 m freshly prepared and kept in a dark place until that moment at a temperature u2266 u2212 18 u00b0 c the weighing bottle was closed but not sealed to avoid a dangerous increase in pressure inside and kept at 4 u00b0 c for 72 hours then it was gradually returned at room temperature and the samples were removed from it c the paper samples were washed repeatedly with diethyl ether to remove any residue of non reacted 2 1 piperidine diazoethane after washing the samples were left to dry under strong aspiration at room temperature on a glass surface for about 6 hours d finally after the solvent was completely removed the samples were conditioned for 1 week in an insulated box t 23 u00b0 c 50 r h the ph of these samples was measured over 3 months to check the effectiveness of the method 0049 fig1 shows the ph trend before treatment dotted line and after treatment continuous line in order to evaluate the effectiveness the present method of deacidification was applied to a.