( 347 ) 



umi soinewluil hilor <also in the ürecii trouulis. Tlic (leeomposilion in 

 the bhie light proceeded about 3 or 4 limes more rapidly than in 

 the green one. 



A similar solution was placed in tubes and troughs consti'ucted of 

 uviol glass, and the light of three uviol lamps was concentrated 

 thereupon by means of a uviol lens of 120 mm. diameter. After 8 

 hours' exposure a measurable quantity of C^Cl^ had already de|)osited. 

 (^Quantitative experiments in a small uviol thermostat and also in a 

 (piartz apparatus with the aid of a cpiartz lamp are now being 

 carried out ; they prove anyhow, that the decomposition-xelocity 

 depends distinctly on the concentration of the solutions. Generally, 

 the action of the ultraviolet light is again a particularly strong one. 



§ 7. Further decompositions are caused by the electric current 

 and by an elevation of tem|)erature. The latter first causes a brown 

 colouration owing to increased hydrolysis ; afterw^ards evolution of 

 CO., and a turbidity due to a deposit of Fc-^ O^, and liberation of 

 chlorofonn. (^)uite analogous, for instance, is, as I noticed, the decom- 

 position of a solution of tliallous-tribromoacetate into CO.^ and CHB)\ 

 when heated at 70°, ciud the p/iotocheniical trfinsforination oï a sohxüon 

 of ferric-tribromoacetate, which always yields 00.^, Fe^ 0^ and 

 hromoform. 



The electrolysis of the ferric salt shows nothing much in parti- 

 cular. The specific resistance of the solutions is great and at first 

 they always tuni brown. At an increased current-density, an evolution 

 of gas takes place at the anode and this gas is nothing else but 

 free chlorine. Simultaneously we can observe at the cathode the 

 formation of a ferrous salt, also the presence of much HCl which 

 causes the resistance to gradually decrease. Hence, both the thermic 

 and the electrolytic decompositions of the ferric salt are different 

 from the photochemical one. 



In regard to the above stated comparisons between the three 

 transformation -form 8 of the ferric solutions, one miglit also imagine 

 that it was i)ractically a question of a photochemical splitting of 

 trichloroacetic acid, in which the i'Vion would exercise its wellknown 

 photocatalytic action. It is, therefore, obvious to also compare this 

 splitting of the CCl^ . CT/^-complex with the thermochemical and 

 its electrolytic decomposition. 



The thermochemical decomiwsition has l)een thoroughly studied ; 

 6'^>., and C'// 6'/, ^ii"e always the main products in the desintegration 

 of the trichloroacetic acid molecule. This happens, for instance, on 

 boiling the solution of the alkali, barium, ihallous and of the ferric 



24 



Procteiiiugi Royal Acad. Amsteidaiu. Vol. XIV. 



