﻿1 30 BACON. 



decomposes pure oxalic acid so slowly, as compared with the speed of the 

 reaction with uranium salts, that the autodecomposition may he alto- 

 gether neglected in the present series of experiments. 



This result is in accord with those obtained by Richardson 2 who found that 

 oxalic acid is only slowly decomposed by sunlight even at 0°, to form carbon mo- 

 noxide, carbon dioxide, and hydrogen peroxide. The reaction does not take place 

 under the red rays of the spectrum alone; sterilization has no effect, so that micro- 

 organisms take no part in it, although it is known that certain microorganisms 

 decompose oxalic acid under proper conditions, to give carbon monoxide, carbon 

 dioxide and water. No hydrogen peroxide is formed in the dark, even if oxygen 

 is present. Dilute sulphuric acid does not decompose oxalic acid in the absence 

 of light, as was proved by drawing air for seven days through a solution of the 

 acid and into one of barium hydroxide, the oxalic acid being kept at 70° to 80°. 

 Dilute sulphuric acid accelerates the decomposition of oxalic acid in the sunlight, 

 for, in seven days, 0.06 gram of carbon dioxide was obtained from 5 grams of 

 oxalic acid. 



The reactions catalyzed by uranium salts are in the great majority of 

 cases well known, taking place with extreme slowness when no catalyzer 

 is present. 



Experiment 1. — August 22. Direct sun from 2 to 2.45 p. m- To determine 

 the effect of varying quantities of uranium salts on the speed of the reaction. 

 Quantities in cubic centimeters. 



(a) 5 grams oxalic acid. 



2.2245 grams crystallized uranium acetate (Kahlbaum). 

 100 cubic centimeters water. 



( b ) 5 grams oxalic acid. 



1.1386 grams uranium acetate. 

 100 cubic centimeters water. 



(a) (b) 



45 40 



When placed in diffused light in the laboratory ( a ) gave no more gas ( b ) 

 gave 2 cubic centimeters. 



Experiment 2. — August 30. Both flasks (a) and (b) were left in partial 

 sunlight for fifteen minutes. One cubic centimeter of gas had collected in each 

 one. On placing the flasks in the diffused light of the laboratory, gas continued 

 to be formed for two hours, the amount being 12 cubic centimeters and 7 cubic 

 centimeters, respectively, for (a) and (b) . After placing a solution in the 

 sunlight it takes some time for the reaction to attain its maximum rate, a fact 

 which has often been noted concerning it. An oxalic acid solution containing 

 uranium salts gives no gas, even at 100°, if it is kept in the dark. 



Experiment 3. — The solutions (a) and (b) were the same; the number of 

 cubic centimeters of gas obtained from the two solutions in the same length of 

 time and under the same conditions of sunlight were: 



(a) 



(6) 



33 



28 



10 



11 



17 



12 



13 



10.5 



33 



28 



'J. Chem. Soc. (1894) 65, 451. 



