estimation of chromium in ferrochrome by means of potassium permanganate gives low results if the theoretical titre number for chromium as recorded in the textbooks (0.310 instead of the empirical number 0.3165) is used. On the other hand, accurate results are obtai:ned by the sodium thiosulphate and potassium &chromate methods. The following shortened sodium thiosulphate process gives iesults accurate to 0.3 per cent;., and can be completed in an hour. The powdered sample