]\lAci.KOi). — l^afe of Oxidation of Acet aldehyde to Acetic Acid . 39 



The following are some results obtained by using this sample. There 

 can be no doubt that there was the pressure of aldehyde in the pure form 

 there, as the para form, boiling at 124° C, could not give a very great 

 pressure at 21 G., but the presence of the para form is small quantities 

 hindered the action. 



The value of h' is not calculated, as it is obviously worthless. 



These experiments show that there has been little action going on. At 

 first the aldehyde was not suspected ; but when the oxygen had been used 

 undried, and dried over calcium-chloride and sulphuric acid, and when the 

 temperature had been raised to 25° C, and still the action did not proceed 

 at a satisfactory speed, it was thought that the fault was due to the alde- 

 hyde. 



A second sample of aldehyde was prepared from the original sample 

 by distilling it with dilute sulphuric acid, so as to break down the para 

 form present. 



Three distilling-flasks were used. The first contained the mixture of 

 dilute sulphuric acid and aldehyde, the second contained calcium-chloride 

 in fairly large quantities, and the third was empty. All the flasks and 

 connecting tubes were carefully washed and steamed out before being used, 

 so as to remove any trace of acid or base which might polymerize the alde- 

 hyde. The flasks were arranged in series. 



The second and third flasks were immersed in ice, while the bath con- 

 taining the first flask was gradually warmed until the water boiled. The 

 distillation was then stopped. The aldehyde distilled over very readily, 

 being so volatile that some of it passed the second flask, and only condensed 

 on reaching the third flask. Any water-vapour was condensed in the 

 second flask and absorbed by the calcium-chloride. When the water round 

 the first flask had boiled it was detached, and the aldehyde which had con- 

 densed in the second flask distilled into the third flask. The temperature 

 was kept down to 25° C, and the latter half of the liquid in the second flask 

 rejected. The purified aldehyde was then transferred into a well-stoppered 

 bottle protected from light, which had been carefully steamed out. This 

 sample held good throughout the series of experiments. 



