378 PROFESSOR A. CRUM BROWN AND DR JAMES WALKER ON THE 



ethers, potassium-hydrogen carbonate. We were thus led to suspect that the success of 

 the method in the case of oxalic ether depended on its well-known decomposability by 

 water. We were inclined to suppose that this was what took place : The water attacked 

 the ether forming alcohol and oxalovinic acid C 2 H 5 0*CO'COOH, and this, being a stronger 

 acid than acetic acid, decomposed the potassium acetate, giving ethyl-potassium oxalate 

 and acetic acid. A simple experiment showed that this explanation is unsound, for 

 Claisen's reaction takes place as well in the absence as in the presence of water. 80 

 grammes of oxalic ether were mixed with the calculated quantity (53 grammes) of 

 potassium acetate and 160 grammes of alcohol, and boiled, with an inverted condenser, 

 on the water-bath. After half an hour a white precipitate began to form. The boiling 

 was then continued for another half hour, when the liquid was cooled and filtered. The 

 weight of the precipitate, after drying in vacuo, was 60 grammes. The filtrate on being 

 boiled for a further half hour on the water-bath, deposited 5 grammes of precipitate. 

 The filtrate was then evaporated, when an additional quantity of salt crystallised out. 

 The salt was pure ethyl-potassium oxalate. 



0'3024 gramme of the salt gave 02014 gramme of potassium sulphate. 



Calculated for KC 4 H 5 4 . Found. 



K 250 249 



A perfectly satisfactory yield can therefore be obtained by working with alcoholic 

 solution. 



In order to see if the reaction would go further, we heated ethyl-potassium oxalate 

 and potassium acetate, in molecular proportion, with enough alcohol to keep everything 

 in solution at the boiling-point. After two hours' boiling, the liquid was cooled, and the 

 salt which had crystallised out separated by filtration. A potassium determination of 

 the dried salt gave 26 '9 per cent, potassium. Potassium oxalate contains 47 per cent, 

 potassium. The ethyl-potassium oxalate is therefore scarcely at all attacked by potassium 

 acetate in alcoholic solution. 



As oxalic acid is usually regarded as the first term in the malonic acid series, it 

 seemed of interest to see how its ethyl-potassium salt would behave on electrolysis, because, 

 as in this case R" = 0, the ether produced should be oxalic ether itself. 



We subjected a solution of 25 grammes of ethyl-potassium oxalate in 15 grammes of 

 water to electrolysis. The solution remained colourless, but no ether was formed. 

 Analysis of gas given off at the electrodes showed that the anion was oxidised to carbonic 

 acid, water, and ethylene. No other products were contained in the gas given off at the 

 anode. The presence of ethylene was confirmed by the formation of ethylene bromide. 



2C 2 H 6 OCOCOO- +0 = 2C 2 H 4 + H 2 + 4C0 2 , or perhaps 

 2C 2 H 5 OCOCOO- = C 2 H 4 + 2C0 2 + C 2 H 5 OCOCOOH. 



Experiments were also made with methyl-potassium oxalate. This salt can be easily 

 prepared by the same method as was used for the preparation of the corresponding ethyl 

 compound. Potassium acetate, dissolved in methyl alcohol, and methyl oxalate were 



