IN ETHYL ALCOHOL. 71 



passed carbon dioxide into one of the solutions for a considerable time. 

 There was a small difference in the titration values. In both cases 

 the amount of carbon dioxide passed into the solutions was infinitely 

 more than would ordinarily be present in such solution as we were 

 titrating. 



It was at first thought advisable to use an alcoholic solution of 

 potassium hydroxide for titration purposes. There are, however, 

 several difficulties involved. An approximately tenth-normal solution 

 of potassium hydroxide in absolute alcohol was made up and allowed 

 to stand for a couple of days. The carbonate settled, leaving a clear 

 supernatant solution. But if the bottle was opened even for a very 

 short time the solution became cloudy, and when poured into a burette 

 became white with precipitated carbonate. 



A method of filtering the solution, being a modification of one pre- 

 viously used in this laboratory, was then adopted, together with an 

 arrangement for siphoning the solution out of the bottle into the 

 burette. Figure 23 shows the design of the filtering apparatus. The 

 tower T contains sticks of sodium hydroxide and T' is partly filled 

 with metallic sodium. The former acts as a protecting agent to 

 the latter, which serves both for removing the last traces of carbon 

 dioxide and for drying the air. B is a clean empty bottle which is 

 later interchanged with a bottle filled with an alcoholic solution 

 of potassium hydroxide prepared from freshly distilled alcohol. The 

 tube E is connected with suction, so that dried, purified air passes 

 through the whole system, including the Gooch funnel F, containing 

 asbestos previously washed with an alcoholic solution of potassium 

 hydroxide and then pure alcohol, and through the receiving bottle A. 

 When the system has been thoroughly cleansed with dry air free from 

 carbon dioxide, the stopcocks S are closed, and the bottle B is replaced 

 by the one containing alcoholic potash. The stopcocks are then 

 opened and suction again applied to E. When all the solution has 

 been filtered, A is removed, and, as quickly as possible, the stopper 

 arranged to connect it by a siphon with the burette (fig. 24). It was 

 found necessary to use 8 to 10 drops of the solution of coralline in alco- 

 hol for each titration. Even then the end-point is not quite as sharp 

 and distinct as with phenolphthalein. 



When calculating the concentration of the organic acid in the alco- 

 hol from the values obtained by titrating against ammonia, it was found 

 that a slightly different value for the concentration was obtained from 

 that found from the titrations against alcoholic caustic potash. We 

 decided, if possible, to find the cause of this and to apply any necessary 

 corrections. A known quantity of the standard sulphuric acid was 

 titrated against alcoholic potassium hydroxide, using phenolphthalein as 

 the indicator. Several titrations were made in every case, and then an 

 equal quantity of the acid was titrated against the base, using coralline. 



