0. S. Pulman — Determination of Uranium. 229 



Art. XXI. — The Determination of Uranium and Uranyl 

 Phosjphate hy the Zinc JReductor ; by O. S. Pulman, Jr. 



[Contributions from the Kent Chemical Laboratory of Tale University — CXVIII.] 



E. F. Kern^ has recently proposed a method for determining 

 uranium in which the uranyl salt is reduced to the uranous 

 condition by allowing a warm solution of uranyl sulphate to 

 pass through a long Jones reductor, made by putting in the 

 bottom of a 50^"^^ burette, a layer of broken glass an inch thick, 

 and then placing on this an 18-inch column of 20-mesh amal- 

 gamated zinc. The sulphate solution, in volume from 100 to 

 150*^°"^, and containing free sulphuric acid (1-84) between the 

 ratios of 1 to 6 and 1 to 5 to the total solution, was poured 

 through the reductor and caught in a large Erlenmeyer flask, 

 the titration flask, which was closed by a small funnel and con- 

 tained about a gram of dry sodium carbonate. According to 

 Kern, the solution, which was quite acid, upon coming in con- 

 tact with the dry sodium carbonate liberated carbon dioxide, 

 which filled the flask and prevented the oxidation of the ura- 

 nous solutions. After all the solution had been emptied into 

 the reductor it was followed by about 250°""^ of distilled water. 

 The solution was then diluted to SOO^'"'^ and titrated with a 

 " O'Ol normal potassium permanganate solution," containing 

 3'16 grams of the salt per liter, to a faint red end-reaction. 



The time required for 100'"^' of uranyl solution and 250'^' 

 of water to pass through the reductor was about ten minutes ; 

 for 150^"^^ of uranyl solution and 250^°^^ of water, about twenty 

 minutes. 



From his experiments Kern concluded that the reduction 

 went exactly to the uranous stage of oxidation, the reduction 

 being in all cases complete and proceeding no further when the 

 solutions were twice passed through the column of zinc than 

 -when passed through once. The results obtained were concor- 

 dant with those obtained gravimetrically. In making some 

 tests of this process my experience has been somewhat differ- 

 ent from that of Kern. 



For carrying out the tests an uranium solution containing 

 about six grams of uranic oxide per liter was made from uranyl 

 nitrate which had been purified according to the directions of 

 Kichards and Merigold.f Twenty-five cubic centimeters of nitric 

 acid were added per liter to keep basic salts from separating 

 out. It was standardized in the usual gravimetric way by pre- 

 cipitating the uranium by ammonia and weighing it as UgOg. 



* Jour. Am. Chem. Soc, xxiii, 716. 



f Proe. Am. Acad., vol. xxxvii, JSIo. 14, p. 385. 



