362 



PROCEEDINGS OF SECTION B. 



m. Nitrohenzoic Acid Method. 



A modified combination of the methods of (/) Neish and of {g) Kolb 

 and Ahrle was used. The almost neutral nitrates were taken up in water 

 and any eerie salts reduced by passing H.,S through for 30 minutes. The 

 HjS was boiled off and the solution filtered into a large beaker and 

 diluted to 500-lOOOc.c. A hot solution of analine m. nitrobenzoate was 

 added till a permanent precipitate formed. Excess of m. nitrohenzoic 

 acid (•5-2-0 gram, according to the amount of TbO^) was then added in 

 boiling solution, and about one-fourth this weight of aniline m. nitro- 

 benzoate to neutralise any free mineral acid. As the amounts of ThOa 

 present were approximately known, the amounts of the precipitant 

 necessary could easily be calculated. The amounts correspond in general 

 to four or more times the quantity theoretically necessary. The solution 

 was allowed to settle out on a hot plate, then filtered and washed. The 

 washed precipitate was retransferred to the beaker and treated with 

 excess of dilute KOH solution ; warming for about an hour. It was 

 then filtered off, washed, dissolved in SEHNO,, ; the nitrates evaporated 

 to dryness and the precipitation repeated. The precipitate was partially 

 dried, then ignited in the filter paper and weighed as ThOa. The oxide 

 was perfectly white (generally better than the Na2S203 T)recipitate), and 

 the results seem a little lower than those given by the NajS^Og method. 



As a comparison of the two methods is of interest, I have given the 

 results of the two separately in the table of analytical results. The 

 analyses represent duplicates in all cases. 



Analytical Results. 



Radio-active Measurements. 

 The apparatus is figured in the sketch. The mineral in solution 

 was placed in the horizontal glass tube A, and the emanation escaping 

 from it carried through B, a drying tube. This tube was filled for about 



(/) Neish : " Journal of American Chemical Society," xxvi., No. 7. 

 {g) Kolb and Ahrle: "Zeitschrift fur Augewandte Chemie," 18 (1905), 92-93. 



