CHEMISTRY. 



147 



In his paper in the Oomptes Rendua, lix., 873, 

 64, translated in the Chemical News, January 

 7, 1865, and which treats of the dissociation 

 of carbonic oxide, he remarks that when cer- 

 tain bodies are decomposed at a high tempera- 

 ture, their elements are disposed to unite again, 

 so that peculiar arrangements are necessary to 

 demonstrate the separation of their molecules 

 which has occurred. The decomposition taking 

 place in many bodies by the electric spark is 

 probably due to the great development of heat ; 

 and the reason that it is not in such cases fol- 

 lowed by recombination is, probably, that the 

 small amount of gas heated by the spark is sur- 

 rounded by an atmosphere in movement and 

 relatively cold. [This principle, though 'on a 

 somewhat different scale, would doubtless ap- 

 ply in case of the combustion of meteoric bodies, 

 as suggested in the article ATMOSPHEEE, which 

 see.] 



Using within the dissociation-apparatus a 

 brass tube, and keeping this cooled by a con- 

 tinual stream through it of cold water, while 

 pure dry carbonic oxide was kept flowing into 

 the porcelain tube, and the latter was raised to 

 a high heat, as soon as this reaches the point of 

 redness, the gas, delivered at the opposite end of 

 the porcelain tube into a potash bulb or into 

 baryta water, begins to give evidence of pres- 

 ence of carbonic acid ; and after cooling and tak- 

 ing apart the apparatus, the brass tube is found 

 blackened, on its under surface only, with de- 

 posited carbon, the* quantity of this being in 

 proportion to the amount of carbonic acid col- 

 lected. Evidently, therefore, the carbonic oxide 

 has been separated to some extent into its com- 

 ponents oxygen, most or all of which goes to 

 oxidize another portion of the oxide to the 

 higher degree, and carbon, which is deposited. 

 M. Deville concludes that the molecules rise 

 from the lower part of the highly heated porce- 

 lain tube, being already dissociated (partially 

 decomposed), when the carbon particles, solid, 

 are caught on the cold surface of the metal tube, 

 and are thus withdrawn from the attraction of 

 the oxygen, so that recombination is prevented. 

 He thinks the mode of experiment thus em- 

 ployed should be capable of numerous applica- 

 tions. 



for the dissociation of sulphurous acid (note 

 to the Academy of Sciences, February 13, 1865), 

 the outside of the metallic tube was silvered ; 

 this silvered surface became blackened or sul- 

 phuretted, and also to some extent covered with 

 a layer of anhydrous sulphuric acid ; and the facts 

 of course showed that dissociation of the sul- 

 phurous acid into sulphur and oxygen had oc- 

 curred, a part of the latter going to raise the 

 sulphurous to sulphuric acid. Like effects are 

 produced on the former body by the induction 

 spark. For chlorhydric acid, the silvered sur- 

 face was amalgamated with a small amount of 

 mercury : after some time this prepared surface 

 was found covered with chloride of mercury, 

 while the author succeeded in collecting some 

 hydrogen. Carbonic acid was acted on by the 



induction spark. Placing a ball of phosphorus 

 on the surface of mercury in the endiometer- 

 tube, and continually passing the spark for some 

 days, the carbonic acid was completely disso- 

 ciated, and a small amount of carbonic oxide 

 alone was found in the tube. 



A paper by the same author presented to the 

 Academy of Sciences, May 1, 1865, "On the 

 Phenomena of Dissociation in Homogenous 

 Flames," serves rather to confirm than to ex- 

 tend the knowledge of the constitution of flame 

 already possessed. 



Crystallogenic Force : Phenomena and Ap- 

 plications. M. Kuhlmann discovered some 

 time since that, when substances which crys- 

 tallize with facility, as mannite, and the sul- 

 phates of zinc, iron, and copper, are mixed with 

 a thick solution of gum, or with any other sub- 

 stance interfering with free crystallization, and 

 the mixtures are then spread on glass (previ- 

 ously well cleansed with solution of caustic po- 

 tassa), and exposed to the atmosphere, the grad- 

 ual formation of a dry mass by evaporation of 

 the water is accompanied with the production 

 within the former of the most beautiful arbor- 

 izations. Each solution will produce a well- 

 defined design; although, even under apparent- 

 ly the same circumstances, these are not always 

 identical. Still, the forms assumed are very 

 similar, as in some instances those of -stars, in 

 others of leaves and wreaths ; and the modifica- 

 tions appear to depend on the nature of the salt, 

 strength of the solution, and mode of prepara- 

 tion. M. Kuhlmann also observed that if 

 amorphous substances, as magnesia, or sesqui- 

 oxide of iron or of chromium, be mixed with 

 bodies susceptible of crystallization, and these 

 be added to a gummy fluid, the amorphous sub- 

 stances are drawn into the lines of the crystal- 

 line figure. The force concerned in determin- 

 ing crystalline forms, the author has designated 

 the crystallogenic force. The crystalline figures 

 produced as now described, are remarkable for 

 their instability, the design often quite chang- 

 ing in part or wholly in course of a day, from 

 changes of temperature, humidity of the air, 

 &c. The author accordingly gave much atten- 

 tion to the methods of reproducing and pre- 

 serving the forms, resorting for this purpose to 

 photography, to vitrification on the surface of 

 wares, to engraving or etching in different 

 modes, to impression on paper, &c., and to gal- 

 vanoplastry. 



When designs of the sort described are pro- 

 duced on glass, porcelain, earthenware, iron, 

 &c., the mixture also containing some suitable 

 flux, and heat is then applied, the gummy matter 

 disappears, and the mineral substances forming 

 the figures become incorporated and fixed on 

 the surface of the ware, thus ornamenting it 

 permanently with the crystallogenic design in 

 . relief. The saline solutions being mixed with 

 the easily verifiable chromate of lead, the de- 

 sign acquires a greenish color ; and for various 

 colors the oxides of copper, cobalt, and man- 

 ganese were also used. The insoluble materials 



