Page:Proceedings of the Royal Society of London Vol 4.djvu/160

Rh The ballot for James Joseph Sylvester, Esq., was postponed in consequence of the number of Fellows required by the charter not being present.

The following papers were read, viz. — " On the Constitution of the Resins." Part I. By James F. W. Johnston, Esq., F.R.S.

The object of the general investigation, of which the commence- ment is given in this paper, is to determine the relative composition of the various resins which occur in nature, and to trace the analogies they exhibit in their constitution ; and also to ascertain how far they may be regarded as being derived from one common principle, and whether they admit of being all represented by one or more general formulae.

The chemical investigation of the resin of mastic shows that this substance consists of two resins ; the one soluble, and acid ; the other insoluble, and having no acid properties. The formulae ex- pressing the analysis of each of these are given by the author. He also shows that a series of analyses may be obtained which do not indicate the true constitution of a resin. The soluble resin, when exposed to the prolonged action of a heat exceeding 300° Fahr. is partly converted into a resin containing three, and partly into one containing five equivalent parts of oxygen, the proportion of carbon remaining constant. The same resin combines with bases, so as to form four series of salts ; which, in the case of oxide of lead, consist of equivalents of resin and of oxide in the proportions, respectively, of two to one ; three to two ; one to one ; and one to two. This soluble resin in combining with bases does not part with any of its oxygen ; but if any change takes place in its constitution, it consists in the hydrogen being replaced by an equivalent proportion of a metal ; and formulae are given representing the salts of lead on this theoretical view. By boiling the resin in contact with ammonia and nitrate of silver, or perhaps with nitrate of ammonia, it is converted into a resin which forms a bisalt with oxide of silver, in which there is also an apparent replacement of hydrogen by silver.

The resin next examined is that of dragon's blood : and the con- clusions deduced from its analysis are the following. First, that the lump dragon's blood is the natural and pure resin, while the strained and red varieties, being manufactured articles, are more or less de- composed : secondly, that this resin retains alcohol and ether, as most other resins do, with considerable tenacity ; but that these sol- vents may be entirely expelled by a long- con tinned exposure to a temperature not higher than 200° Fahr. : and lastly, the formulae representing its chemical composition is given.

" Researches in Embryology." — Second Series. By Martin Barry, M.D., F.R.S.E., Fellow of the Royal College of Physicians in Edinburgh. Communicated by P. M. Roget, M.D. Sec. R.S.

The author having, in the first series of these researches, investigated the formation of the mammiferous ovum, describes in this second series its incipient developement. The knowledge at present