OXALIC ACID AND URANIUM SALTS AS A PHOTOMETER. 289 



Table X. 



[Manila, January 11, 1910, 10.15 a. rn. to 1.30 p. m. Sky hazy, 10 per cent oxalic acid, 

 1 per cent uranyl acetate. All solutions made up to 20 cubic centimeters.] 



Number. 



Oxalic 

 acid. 



Uranyl 

 solu- 

 tion. 



Remarks. 



Amount 

 oxalic 

 acid 

 decom- 

 posed. 



1 



2 



cc. 

 5 

 5 

 5 

 5 

 5 

 5 

 5 



cc. 



10 



Control. _ _„.. _. . 



Gram. 

 0. 262 

 0. 02S4 

 0. 0284 

 0.003 

 0.008 

 0.004 





3 



4 





Added 2 drops concentrated sulphuric acid 

 Added 2 drops aniline 



5 



Added 2 drops phenol . 



G 



Colored with malachite green 





Colored with methyl violet 



0.001 







Table XL 



[Manila, November 20, 1909, 10.40 a. m. to 2 p. m. Sun only part of the time. Ten 

 per cent oxalic acid solution. One per cent uranyl acetate solution. All made up 

 to a volume of 20 cubic centimeters.] 



Number. 



1. 

 2 

 3 

 4 

 5 

 6 

 7 

 8 





Uran- 



Oxalic 



ium ! 



acid so- 



acetate 



t lution. 



solu- 





tion. 



cc. 



cc. 



5 



10 



5 



10 



5 



10 



5 



10 



5 



10 



5 



10 



5 



10 



5 



10 



i 



Added. 



Decom- 

 position 

 of oxalic 

 acid. 



Control 



0.05 gram quinine 



0.01 gram cinchonine . 



0.01 gram strychnine 



0.01 gram brucine 



0.01 gram atropine 



0.01 gram morphine 



0. o gram copper sulphate 



Per c< hi. 

 25 

 It) 

 10 

 12 

 22 



:i 



19 



Tables VI, VII, and VIII, show that a certain proportion of hydrogen ions, as 

 measured by phenolphthalein, are necessary for this reaction. This is probably to 

 be interpreted in the sense that the reaction takes place as long as uranyl salt is 

 present. The hydrogen ions per ,ie probably have no effect, as increasing their 

 number very markedly did not accelerate the reaction, as shown in Table IV. 



Table IX, in which the same series of measurements was repeated three times, 

 demonstrates that increasing the surface of the solution increases the rate of 

 reaction; and also that diluting the solution (No. 6) increases its rate. The 

 two observations, Table V, Nos. 8 and 0, which seem to contradict this statement, 

 are probably abnormal because of the fact that the solutions became concentrated 

 through evaporation. In the experiments given in Table IX, the volumes were 

 kept constant to avoid the disturbing factor of change of concentration. In Table 

 IX, No. 7, fluorescein was added in the hope that, as it was known to absorb light 

 energy, it would assist the uranyl salt in decomposing the oxalic acid, although 



