Tahmta, 1969, Vol. 16, pp. 1383 to 1391. Peraamon Press. Printed in Northern Irc!and MICRODETERMINATION OF NITRATES AND NITRAMINES-I zyxwvutsrqponmlkjihgfedcbaZYXWVU TITRIMETRIC METHODS BASED ON THE REDUCTION WITH IRON( TITANIUM(III), AND A MIXTURE OF BOTH WILLIAMIBRAHIM AWAD and SAAD S. M. HASSAN Research Microanalytical Laboratories, Chemistry Department, Faculty of Science, Ain Shams University, Cairo, U.A.R. (Received 13 September 1968. Revised 24 March 1969. Accepted 23 April 1969) Summary-Organic and inorganic nitrates are satisfactorily determined on the microscale by reduction with Fe(H). Titanium(II1) reduces the nitrates in strongly acidic, citrate-buffered, and acetate-buffered media with the comsumption of 3, 6 and 8 equivalents respectively of Ti(II1) per nitrate group. Nitramines are determined by reduction with a mixture of Ti(II1) and Fe(I1). Determination of nitrates and nitramines by frans-nitration with salicylic acid is suitable on the microscale. A new electrolytic reduction automatic microburette was devised for the reduction, storage and use of the titanium(II1) solution. DETERMINATION of the nitrate group in both organic and inorganic substances by the commonly used methods can lead to many difficulties, and little information is available about the microdetermination of this group. The titrimetric methods that have been proposed are based on reduction with Devarda’s alloy,1*2 iron(II),3*4 vanadium(II),5 chromium(II),6~7 tin(II),**g and titanium(III).lO*ll Acid-base titration in non-aqueous media has been also described. l2 However, most of these methods are either applied on the macro scale or to inorganic nitrates only. In the present work, micro-methods involving iron( titanium(III), and a mixture of both are examined. Apparatus EXPERIMENTAL A new electrolytic reduction automatic microburette has been devised (Fig. 1). The new burette is used as follows. Titanium(W) sulphate solutiotP (O.lM, 500 ml), is introduced into the burette reservoir and the electrodes are inserted and connected to a 6-V battery as shown, with cathode immersed. After 34 hr reduction the electrodes are removed and the solution is diluted to about O.OSM with freshly twice distilled water. About 150 g of amalgamated zinc, 10 ml of concentrated sulphuric acid and 30 g of ammonium sulphate are added and carbon dioxide is bubbled through slowly overnight. A stream of carbon dioxide from a cylinder is passed for 5 min via tap Tl and B with taps T, and Ts open, in order to displace the air from D, B and the burette. The two free necks of the reservoir are then closed with stoppers and tap Tl is connected via C so that the carbon dioxide forces the titanium solution in the flask into the burette through E. The burette is washed out several times in this way. This procedure is applied after every reduction. For titrations the burette is filled and the pressures inside and outside the reservoir are equalized by switching tap Tl several times between Band C, and then the tap is left connected via B throughout the titration. Reagents All the reagents were of analytical grade unless otherwise specified. The trans-nitration mixture consisted of 50 g of salicylic acid, 450 ml of concentrated sulphuric acid and 50 ml of glacial acetic acid. 1383