Royal Academy of Sciences of Paris. 139 



of its utility in separating soda from potash, as above-mentioned, 

 it will necessarily become in great request. 



Action of Vegetable Substances, Gum, Sugar, fyc. in contact with 

 Metallic Oxides. On the 2d May, M. Becquerel communicated to 

 the Academy a very interesting paper on carbonate of lime in crys- 

 tals, and on the simultaneous action of saccharine and mucilaginous 

 matters upon the oxides of certain metals, obtained through the me- 

 dium of alkalies and earths. M. Becquerel has, for a considerable 

 period, directed his attention to the means of submitting organic 

 substances to the action of electric currents, with the view of ascer- 

 taining the causes of some of the phenomena observable in those 

 substances, particularly that of fermentation. It was already known, 

 from the experiments of Cruikshank and Daniell, that on exposing 

 a solution of sugar and lime in water to the action of the atmosphere, 

 small crystals of carbonated lime are produced on the surface ; 

 but the cause of this phenomenon was entirely unknown, although 

 it was supposed that the carbonic acid might perhaps be supplied 

 by the atmosphere. M. Becquerel, however, has, by means of the 

 following experiment, ascertained the real source of the acid. He 

 plunged into a wide-mouthed bottle, filled with barytes water, 

 two tubes, (the lower parts of which were stopped with moistened 

 barytes,) filled, the one with a solution of lime and sugar, and the 

 other with a solution of sulphate of copper. The liquid contained 

 in the first tube was connected with the positive pole of a voltaic 

 pile, by means of a plate of platina, and that in the second tube 

 with the negative pole, by means of a plate of copper. The 

 moment this communication was established, the sulphate of copper 

 was observed to be decomposed, the copper was precipitated in a 

 metallic state on the copper plate, the sulphuric acid was absorbed 

 by the barytes, and the oxygen was transported to the positive pole ; 

 where, by a re-action on the carbon of the sugar, it produced car- 

 bonic acid, which was immediately combined with the lime. After 

 the lapse of some days, small prismatic crystals of carbonate of lime 

 were observed on the plate of platina, and continued to increase as 

 long as there remained any lime in the solution. Gum, the compo- 

 nent parts of which are nearly similar to those of sugar, produced 

 the same effect. In both cases, those portions of the vegetable sub- 

 stance which do not tend to the production of the carbonic acid, or 

 of the water of crystallization of the carbonate, are converted into 

 acetic acid. M. Becquerel was next led to examine the simultaneous 

 action of saccharine and mucilaginous substances upon the metallic 

 oxides, through the medium of the alkalies and the earths. If 

 hydrate of copper be acted on by water and lime, with the aid of 

 heat, it becomes black, and probably passes into an anhydrous 

 state ; but if a very small quantity of sugar be added, a portion 

 of the oxide is dissolved, and the liquid assumes a beautiful blue 

 tint, similar to that of a solution of oxide of copper in ammoniac. 



