ARSENIC. Kayser and Runge: Abhandl. königl. Akad. Wissensch. zu Berlin,' 1893. The spectrum of arsenic shows no lines in the visible spectrum, but between 3000-2000, the lines of arsenic, and in particular 2288-19 and 2009-31, constantly appear as impurities in other metals and in the carbon poles. The lines 2288-19 and 2009-31, given as copper lines (Report, 1893, pp. 397, 398). appear to be due to arsenic. The spark-spectrum of arsenic, on the other hand, shows some fifty lines in the visible portion. Isomeric Naphthalene Derivatives.-Eighth Report of the Committee, consisting of Professor W. A. TILDEN and Professor H. E. ARMSTRONG. (Drawn up by Professor ARMSTRONG.) The Conversion of Sulphochlorides into the corresponding Chloroderivatives. In the case of naphthalene derivatives no interaction is of greater practical importance than that which occurs when sulphochlorides are heated with phosphorus pentachloride, whereby they are converted into chloro-derivatives. At one time it was argued that reliance could not be placed on this interaction as a means of determining constitution, but of late years no such objection has been raised, and the idea that isomeric change may attend the displacement of the sulphonic radicle by chlorine appears to have been abandoned. The results obtained, especially by Cleve and by Dr. Wynne and the writer, are so uniformly consistent inter se that, bearing in mind the extent of the field covered, there is no longer room for doubt. Observations made during the past year are of interest as throwing light on the nature of the interaction. There have long been instances on record of the conversion of sulphochlorides into corresponding chloro-derivatives and sulphur dioxide (RSO2Cl=RC1+SO2) by mere distillation. The successful use recently made of this method in the writer's laboratory in preparing chloro- and bromo-derivatives of camphor by Dr. Kipping and Mr. Pope has led him and Dr. Wynne to systematically study the behaviour of naphthalene sulphochlorides, which they had long known underwent decomposition, evolving sulphur dioxide, when heated. The conclusion arrived at is that, in all probability, phosphorus pentachloride acts merely by facilitating the resolution of the sulphochloride into sulphur dioxide and the chloro-derivative by attacking the former and converting it into thionyl chloride; and that, in fact, the chlorine in the chloro-derivative is not improbably the original chlorine of the sulphochloride and not chlorine derived from the pentachloride. In most cases the amount of chloro-derivative produced by directly distilling the sulphochloride is inferior to that obtained by means of pentachloride, as the decomposition is facilitated by the chloride, and therefore takes place at a lower temperature in its presence. There is always more or less of a resinoid condensation product formed on distilling the sulphochloride, but the amount is in some cases very small, while in others practically nothing else is obtained. On the other hand, in the case of compounds which are very readily chlorinated, the method permits of the production of chloro-derivatives corresponding to the sulphochlorides which are almost unprocurable from them by the ordinary method. For example, 1 1'-chloronaphthalenesulphonic chloride yields a very large proportion of 1: 1'-dichloronaphthalene when distilled, although when heated with phosphorus pentachloride it is almost entirely converted into 14: 1' trichloronaphthalene. The a-sulphochlorides appear all to decompose more readily and to yield a larger proportion of chloro-derivative than do the B-sulphochlorides. It may be added that, taking into account the readiness with which change occurs during sulphonation, the non-occurrence of isomeric change on distilling sulphochlorides is probably significant. Bromo-derivatives of Naphthalene. The conversion of naphthalene sulphobromides into corresponding bromonaphthalenes by means of phosphorus pentabromide is attended with great difficulty, as the bromide frequently acts almost exclusively as a brominating agent, owing to the readiness with which it is resolved into the terbromide and bromine. Far |