390 



RECENT PROGRESS IN PHYSICS. 



Fi?. 158. 



duces muriatic acid. But these acids are also oxydized at the positive 

 pole, and thus this process of oxydation is continued until the whole 

 of the chlorine in the solution is either changed into per-chloric acid 

 or evolved in the gaseous form. 



These phenomena of decomposition may be explained by supposing 

 the decomposition of water to be the primary, the oxydation of the 

 acid the secondary, effect. Daniell's theory of the electrolysis of solu- 

 tions of salts is here entirely inapplicable. According to this theory, 

 the salt should be considered as K -\- (C, CI3) 83 Og ; the acid combi- 

 nation at the positive pole ought to be separated into two equivalents 

 of sulphuric acid and the insoluble sesqui-chloride of carbon Cj CI3. 



The oxydation of the chlorine absolutely requires the supposition 

 of a primary decomposition of water. 



§ 1 80. Eledrolysisof valerianic and acetic acid. — Kolbe, by subjecting 

 organic substances to electrolysis, and accurately observing the course of 

 their decompositions, has initiated a method which promises to become 

 of great importance to science. We shall here follow Kolbe's researches 

 as far as is necessary for the comprehension of the electrolytic part of 

 the phenomena^ without entering upon the discussions of the consti- 

 tution of the organic substances examined. 



Kolbe's memoir on the electrolysis of organic compounds is to be 

 ibund in full in the Annalen der Chemie und Pharmacie, vol. LXIX, 

 page 257. 



As free valerianic acid is a bad 

 conductor of the galvanic current, 

 Kolbe used for the electrolytic de- 

 composition a concentrated aque- 

 ous solution of its potassa salt. 

 The decomposition-apparatus was 

 arranged, as shown in fig. 158. 

 The glass-cylinder was about 11 

 inches high and 2\ inches wide. 

 The exterior metallic cylinder 

 was of copper, the interior of 

 platinum foil. The copper cyl- 

 inder was connected with the 

 negative, the platinum cylinder 

 with the positive pole of a bat- 

 tery, consisting of four Bunsen's 

 cups. 



When this apparatus was filled with a solution of valerianate of 

 potassa KO + (Cg H^) C2 O3, and the current passed, as indicated, 

 through the fluid, a brisk evolution of gas took place at both the poles, 

 and at the same time light oily drops of a slightly yellow tinge, and 

 an agreeable etheric odor appeared upon the surface of the fluid. The 

 very odoriferous gases escaping contained (after all atmospheric air had 

 been expelled from the apparatus) not a trace of oxygen. The mixture 

 of gases consisted of hydrogen, carbonic acid, and a third gas, burning 

 with a brilliant flame, and which gave to the mixture its peculiar odor. 



After the action of the current had continued for several hours, the 



