I Acenaphthenequinone has been mono- brominated and the product shown to be 4- bromo- acenaphthenequihone, the direct bromination described being the best method of preparing the latter compound. Various derivatives, have been prepared, including 4- bromo- naphthalic anhydride by oxidation with hydrogen peroxide in alkaline solution. TI The bromination of naphthalic anhydride has been studied. The product obtained by the action of bromine in a mixture of oleum and concentrated sulphuric acid has been shown to be 3- bromo- naphthalic anhydride and not the 4- bromo- derivative as has hitherto been assumed. It has been shown that 3- sulpho -naphthalic anhydride is not formed as an intermediate stage in this reaction. The same compound was obtained by the action of bromine on naphthalic anhydride in a sealed tube, and an improved method of preparing it, namely by the action of bromine in concentrated nitric acid, is described. Proof of the constitution of the 3- bromo-naphthalic anhydride consisted in a direct comparison with a specimen prepared from 3- nitro-naphthalic acid by reduction, diazotisation and treatment with cuprous bromide. Further confirmation follows from the work on the mercuration summarised below. On the other hand, by the bromination of naphthalic acid (as alkali salt) by bromine in presence of alkali hypobromite, 4- bromo- naphthalic anhydride has been prepared. Derivatives of the- two mono -bromo- naphthalic anhydrides have been prepared for purposes of comparison. III Mercurations of 3- bromo- and 4- bromo- naphthalic anhydride have been carried out. From the mixture obtained by hydrolysis of the mercuration product from the former, the hitherto unknown 3- bromo -naphthoic acid was obtained, its constitution being proved by direct comparison with a specimen prepared from 3- nitro-naphthoic acid by reduction, diazotisation and treatment with cuprous bromide. Hydrolysis of the mercuration product from 4- bromo- naphthalic anhydride gave a mixture from which 5- bromo -naphthoic acid was isolated. This compound is already described in the literature, being prepared by the bromination of naphthoic acid. Identity of specimens from the two sources was proved. IV (a) The introduction of more than one atom of 143. bromine into acenaphthenequinone and naphthalic anhydride respectively has been studied. In each case a tribromo- derivative has been obtained, the orientation of the bromine atoms being the same, since the tribromo- acenaphthenequinone on oxidation gave a tribromo- naphthalic anhydride identical with that obtained directly from naphthalic anhydride. It has not yet been possible decisively to prove the positions of the bromine atoms. (b) The mono- nitration of 4- nitro -naphthalic anhydride (obtained by oxidation of 4- nitro -acenaphthene) has been shown to give 4:5- dinitro- naphthalic anhydride. On the other hand when 4- bromo- naphthalic anhydride is nitrated it yields 3- nitro -4- bromo- naphthalic anhydride. To prove the constitution of the latter compound it was synthesised in a manner showing its constitution, being prepared by the oxidation of 3- nitro -4- bromo- acenaphthene, which was obtained from the already known 3- nitro -4- amino -acenaphthene by diazotisation and treatment with cuprdus bromide. V The condensation of naphthalic anhydride and its substituted derivatives with o- phenylenediamine has been shown to take place in glacial acetic acid with loss of two molecules of water to give 1:8- naphthoylene- l:2- benziminazole and its derivatives. When the naphthalic anhydride was of a symmetrical structure, a well- defined derivative was obtained, but unsymmetrical anhydrides gave mixtures of compounds which could not be separated. VI (a) A study has been made of methods for the preparation of acenaphthenone, some new methods being described. The best preparative method was found to be the reduction of acenaphthenequinone oxime, which can be prepared directly from acenaphthene. Reduction of acenaphthenequinone phenylhydrazone also provides a serviceable method. In connection with this work the preparation of acenaphthenequinone anil, Wolff's reaction on ace - naphthenequinone semicarbazone, the action of ammonia on l:l- dichloro- acenaphthenone and that of methylamine on acenaphthenequinone have been investigated. The imide and methylimide expected in the last two cases respectively were not obtained, condensation between two molecules taking place to form azine derivatives. (b) Acenaphthenone on direct bromination yields first 1- bromo- acenaphthenone and on further bromination l:1- dibromo- acenaphthenone. Attempts to evolve indirect preparative methods for bromo- derivatives of acenaphthenone substituted in the nucleus were not successful. (o) By nitration of acenaphthenone a compound has been obtained which on oxidation yields 4- nitro- naphthalic anhydride. definite conclusion with regard to its constitution has not however been reached. VII A new method is described for the preparation of biacenaphthylidenedione, this compound resulting quantitatively by the action of sodium sulphide on 1:1- dichloro- acena-phthenone in alcoholic solution. By reduction of biacenaphthylidenedione with sodium hydrosulphite in alkaline solution, or with iron filings and glacial acetic acid, a new compound, which also results from the reduction of acenaphthenequinone with hydriodic acid and red phosphorus at 160-170° has been obtained. It has been proved to be l:1`- diacenaphthenonyl by synthesis of the latter by a method showing its constitution, namely by the action of copper bronze in boiling xylene on 1-bromoacenaphthenone.