﻿CATALYSIS. 131 



It is therefore evident that the relative amounts of uranium salt only slightly 

 affect the speed of the reaction. 



Experiment 4. — Two cubic centimeters of concentrated nitric acid added to 

 (&). Quantities in cubic centimeters. 



(a) 



(6) 



32 



27 



16 



11.5 



Experiment 5. — Two quantities of solution (a) were compared with a solution 

 containing 5 grams of oxalic acid and 2 grams of pitchblende, dissolved in the 

 smallest possible quantity of nitric acid. The solution containing pitchblende (b) 

 decomposed the oxalic acid at one half the rate of (a) . 



Experiment 6. — 



(a) 5 grams oxalic acid. 



100 cubic centimeters water. 



(b) 5 grams oxalic acid. 



2 grams thorium nitrate. 

 100 cubic centimeters water. 



In one hour and thirty minutes in sunlight, each gave 0.5 cubic centimeter gas. 

 The thorium nitrate was but slightly dissolved and the solution was very milky 

 in appearance. 



Experiment 7. — To each of solutions (a) and (b) from experiment 6, 5 cubic 

 centimeters of concentrated nitric acid was added partially to dissolve the salt 

 of thorium, the time in sunlight being two hours. Quantities in cubic centimeters. 



(a) (b) 



1.2 14 



As the thorium salt is only slightly dissolved, this fact may have rendered 

 the reaction in (6) slower than it otherwise would be, but nevertheless it is 

 interesting to note that the radio-active thorium salts catalyze a solution of oxalic 

 acid. 



Experiment 8. — It was thought that possibly the increased rate of reaction 

 observed in (b) , experiment 7, might be ascribed to the action of finely divided 

 particles of thorium nitrate as catalyzers. Hence, two flasks were prepared each 

 containing 5 grams of oxalic acid dissolved in 100 cubic centimeters of water. To 

 one of these freshly precipitated barium sulphate was added; to the. other, finely 

 ground silica, but no gas was obtained in either flask, even in the sunlight. 



Experiment 9. — October 22, p. m. 



(a) 4.31 grams pitchblende from Joachimsthal, containing 1.126 

 grams uranium dissolved in 5 cubic centimeters of con- 

 centrated nitric acid. 

 5 grams oxalic acid. 

 100 cubic centimeters water. 

 (&) 2 grams uranium acetate containing 1.126 grams uranium. 

 5 cubic centimeters concentrated nitric acid. 

 5 grams oxalic acid. 

 100 cubic centimeters water. 



Quantities in cubic centimeters. 



Time. 



(a) 



(b) 



3.25 to 3.40 



5.5 



0.5 



3.40 to 3.55 



19.0 



1.0 



