﻿")*2cS Dr. T. Ewan on the Rate of Oxidation 



through FH until it is full of oxygen. The tap H is then 

 quickly opened, to admit the oxygen, closed again, and 

 the pressure read off. Further readings are then made 

 from time to time until the reaction is ended. The gases 

 take some time to diffuse into each other, so that the velocity 

 of the reaction was frequently rather small at the beginning. 



The calculation of the experiments required a knowledge 

 of the composition of the gas which remained in the apparatus 

 at the end of the experiment. As soon as the last reading of 

 the pressure had been made, therefore, a very dilute solution 

 of caustic potash was allowed to flow into the apparatus from a 

 weighed flask. The difference between the volume of the 

 apparatus (determined by weighing it full of water) and the 

 volume of the caustic-potash solution drawn into it, gave the 

 volume of oxygen and nitrogen contained in the residue. 

 Caustic potash was used in order to polymerize any aldehyde 

 left. 



The mixture of oxygen and nitrogen was then transferred 

 to a graduated tube, and shaken with an alkaline solution of 

 pyrogallol. The part which was left unabsorbed was taken to 

 be nitrogen. The transference of the residual gas from the 

 bulb A to the graduated tube was effected by running water 

 in through the capillary tube K after breaking off its sealed 

 end. 



In many of the earlier experiments a comparatively large 

 quantity of gas remained which was not absorbed by the 

 solution of pyrogallol and caustic potash. It was noticed, 

 however, finally that this gas was inflammable, and that its 

 formation was accompanied by some action of the mixture of 

 aldehyde and oxygen on the mercury in the manometer, a 

 white substance, which was insoluble in water, being formed. 



On protecting the mercury by placing a very small quantity 

 of bromnaphthalene over its surface, no formation of the 

 white substance occurred, and the gas which remained unacted 

 upon by the pyrogallol was much smaller in quantity than 

 formerly, and no longer inflammable. It is probable also that 

 the reaction is accelerated by light. The following experi- 

 ment may be quoted in support of this view. The temperature 

 was 19°-98 to 20°*07. 



The constant K was calculated by means of equation (5), 

 which was found to apply to this reaction. The value of the 

 constant appears to be influenced by the brightness of the 

 light. For this reason the experiments were finally made in 

 the dark. It appears also to be of some importance to keep 

 the apparatus as clean as possible. It was generally allowed 



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