The Use of Perchloric Acid as an Aid to Digestion in: the Kjeldahl Nitrogen Determination
Journal of Industrial & Engineering Chemistry
tendency of such solutions to show a lowered oxidizing capacity after standing. It occurred to the writers that this might be due to a slow reaction with traces of hydrogen peroxide which had not been decomposed by boiling the alkaline solution. To test this point, the solution obtained by dissolving the fused mass from a Bample of ferrochromium was boiled 30 min., made up to volume, and on analysis found to contain 63.42 per cent chromium. After 4 days the apparent percentage of chromium was
... e of chromium was 62.10 and 62.20. A solution of another fusion was boiled 2 hrs. before acidification. The analysis of the freshly prepared solution gave A N D ENGINEERING CHEMISTRY Vol. 13, No. 11 63.53 per cent chromium. After 4 days the apparent percentage of chromium was 63.05 and 63.15 per cent. It is thus clear that even boiling 2 hrs. does not give a stable solution. SUMMARY In this paper a method has been described for determining chromium in ferrochromium in which the chromate produced by oxidizing either with sodium peroxide or with silver nitrate and ammonium persulfate is titrated with ferrous sulfate, using an electrometric end-point. The procedure described has been in use in this laboratory for several years.