Three methods for the determination of carbonyl in hydrocelluloses and in oxidized cellulose are given in this section. Two of them, an oximation and a reduction with sodium borohydrate, are applicable to samples of high carbonyl content. In each case, the amount of excess reagent is determined; to obtain precise results, the amount of reagent in a blank run must not be too large in relation to the amount consumed. In the third method, the amount of reagent consumed, a substituted hydrazide, is determined directly; a large excess of reagent can be used, and this method is more suitable for low carbonyl values.