610 Dr. B. B. Boltwood on 



of Herzf eld & Korn *. A paper by Barker f states that 

 several "competent chemists," to whom samples from North 

 Carolina were submitted for analysis, reported that no 

 uranium was present. Zerban J has offered further data on 

 the composition of this mineral, in a paper in which the 

 chemical method employed for the analysis is described. He 

 was able to separate O038 per cent, of U 3 8 from North 

 Carolina monazite, and O040 per cent, of U 3 8 from the 

 Brazilian material. 



The analytical method used by Zerban was criticised by the 

 late Clemens Winkler § ; and the experience of the writer has 

 further confirmed the doubt as to its suitability for the 

 determination in question. It was found, for example, that 

 the addition of 0*4 per cent, of uranium to the original 

 material failed to seriously affect the quantity of uranium 

 ultimately separated when the analytical process involved 

 the preliminary removal of the rare earths by precipitation 

 with oxalic acid. The quantities of uranium obtained by 

 this method varied from mere traces to amounts corresponding 

 to several hundredths of a per cent, of the original mineral, 

 and were to some extent dependent on the quantities of free 

 sulphuric acid contained in the solutions from which the 

 oxalates were precipitated. It seems probable that the 

 greater part of the uranium is precipitated with the oxalates, 

 since a relatively large amount of free mineral acid is 

 required to retain uranium in solution in the presence of 

 considerable quantities of phosphoric acid. 



The results given in this paper were obtained by the use 

 of the general method of analysis already described (p. 605), 

 using only 1 gram of the sample ; and the identity of the 

 uranium separated was fully established by the well-known 

 reactions with potassium ferrocyanide and hydrogen peroxide. 

 A control analysis conducted with 10 grams of the North 

 Carolina material demonstrated that the final uranium 

 phosphate precipitate did not contain appreciable quantities 

 of elements precipitated by oxalic acid and ammonium 

 oxalate (thorium, zirconium, &c.), and gave uranium equivalent 

 to 0'399 per cent, (corresponding to the ratio 221). 



In determining the activity of the emanation it is possible 

 to measure the leak of the electroscope with a fair degree of 

 accuracy to the second place of decimals. When five grams 

 of monazite (North Carolina) were used, the leak observed 

 in two duplicate experiments was equal to 4*40 divisions per 



* Chemie d. selt. Erden. 



t Am. Journ. of Science, xvi. p. 161 (1903). 



X lierichte d. D. Chem. Gesell. xxxvi. p. 3911 (1903). 



§ Ibid, xxxvii. p. 1655 (1904). 



