Smith.] 



430 



[Nov. 18, 



characteristic red-brown precipitate of uranium ferrocyanide appeared. 

 Tliis suggested the possibility of obtaining a quantitative method for the 

 estimation of borii acid. I, therefore, dissolved 4.18 grams of uranium 

 nitrate in one litre of water, and 1.16 grs. of well- crystallized borax in 

 250 c.c. water. The uranium solution was then placed in a burette and 

 carefully added to definite portions of the borax solution until a drop of 

 the mixture, added by means of a thin glass rod, to a drop of a concen- 

 trated potassium ferrocyanide solution, on a porcelain plate, gave a red- 

 dish-brown color. The first distinct coloration was regarded as the final 

 reaction. The following results were obtained : 



1. 5 c.c. of the borax solution required 8.8 c.c. uranium nitrate. 



8.9 " 

 3. 

 4. 

 5. 



6. " •' " " 8.8 " 



7. 



10. 10 c.c. 

 11. 



^.8 " 



17.7 

 17.6 



A second uranium nitrate solution, containing 8.6267 grams nitrate in 

 500 c.c. of water, was standardized as above with a borax solution (con- 

 taining .9051 grams borax in 250 c.c. water). The results were as 

 follows : 



1. 5 c.c. borax solution required 1.85 c.c. uranium nitrate. 



2. " 

 3 ,. 



4. " 



5. " " " " " " 



From this we discover that 1 c.c. of uranium solution equaled .004917 

 grams B2O3. 



To test the accuracy of the method, I dissolved 1.1762 grams freshly 

 crystallized borax in 250 c.c. of water, and titrated portions of it with the 

 above standardized uranium solution: 



1. 10 c.c. of borax solution required 4.0 c.c. uranium solution. 



3.5 " 



3. " " " 3.4 " 



4. " " " 3.5 " 

 5. 

 6. 

 7. 



