The reactions between nitrogen pentoxide and, various organic compounds in different solvents have been examined. The results obtained in these nitrations have been compared to the results obtained by previous workers using different nitrating reagents (cf. Table, pp. 116-122). The practical advantages of the use of nitrogen pentoxide have been noted, and theoretical conclusions have been drawn from the results obtained as to the nature of its nitrating mechanism In conclusion, the author wishes to express his indebtedness to Dr Neil Campbell for his advice and constant interest throughout the course of this work, and to make grateful acknowledgement to the Department of Scientific and industrial Research for a Maintenance Allowance for the years 1935 -37.