ANAEROBIC RESPIRATION 77 



percentage by weight is calculated on the basis of the specific 

 gravity of alcohol. 

 2. Oxidation with Permanganate in Alkaline Solution.^— 



This determination of alcohol is based on the following reaction : 



i2KMn04 + 12KOH + CH3— CH2OH = i2K2Mn04 + 



9H2O + 2CO2. 



Alcohol is thereby burned to carbon dioxide and water. The 

 following solutions are prepared: 



(a) A solution of 39 g. KMn04 in 4 liters of water. 



(b) A solution of 80 g. oxalic acid in 4 liters of water. 



(c) A solution of 150 g. NaOH in i liter of water. 



(d) A solution of 2 vols. cone. H2SO4 in 5 vols. dist. water. 



(e) A solution of 3. 182 g. purest KMn04 (Kahlbaum preparation " Zur Analyse mit 

 Garantieschein," or ordinary preparations twice recrystallized) in i liter of water. 

 I cc. of this solution yields 0.8 mg. of oxygen. 



The alcoholic content of the solution to be tested must not 

 exceed 0.2%. The determination is carried out as follows. 

 100 cc. of solution a and 40 cc. of solution c are placed in a 700 

 cc. flask. The mixture is heated to boiling and then exactly 

 5 cc. of the alcohol solution are poured in. The whole is boiled 

 I minute and then 100 cc. of solution h and 40 cc. of solution d 

 are added to the hot liquid. This causes an immediate colora- 

 tion of the liquid. The mixture is titrated with solution e and 

 the amount A of cubic centimeters of permanganate solution 

 used is noted. 



The whole operation is now repeated with a 0.4% sugar solu- 

 tion substituted for the solution of alcohol. 5 cc. of this solu- 

 tion should theoretically use up 28.05 cc. of solution e. In 

 practice a larger quantity of permanganate is used on account of 

 its decomposition in boiling with sodium hydroxide. The 

 oxidation of the sugar is for the purpose of determining the 

 correction B — 28.05 which must also be considered in the deter- 

 mination of the alcohol. The desired amount of alcohol is A — 

 (B — 28.05) ■ 0-384 mg. It is obvious that the control analysis 

 needs to be carried out only once for a given solution. 



The chemical as well as the physical methods of determination 

 of alcohol depend upon the assumption that only pure ethyl 

 alcohol is contained in the distillate. Actually the basic, as^^;^-— 77-. 



1 Barendrecht, H. P. Z. f. analyt. Chem. 52: 167. 1913- / v V' - ' C 



Lj i L I B R A R 



