THE ANALYSIS OF BRONZES AND 

 BEARING METALS* 



Bv H. E. Walters and 0. I Affelder. 



Bronzes. — Weigh 1 gram of the sample (^ gram if the lead 

 is over 15$ into a No. 2 beaker, cover with a watch-glass, add 10 

 cc. nitric acid (Sp. Gr. 1.42) and warm until all is dissolved. When 

 in solution, add 40 cc. hot water and boil five minutes, filter, wash 

 with a 2$ nitric acid solution, burn and weigh as Sn0 2 . To the 

 filtrate add 25 cc. strong ammonia and heat to boiling, then add 

 about 5 grams ammonium persulphate and boil from 5 to 10 min- 

 utes. Make acid with sulphuric acid, filter and wash with hot 

 water. The lead will remain on the filter as lead peroxide. Trans- 

 fer the precipitate and lead to a beaker in which the precipitation 

 was made, add water and stir well to disintegrate the filter paper. 

 Dilute to 600 to 700 cc. with cold water, add about 3 grams potas- 

 sium iodide and some starch solution. When all the iodide is dis- 

 solved, add 10 cc. hydrochloric acid, stir well and titrate with 

 1/20 normal solution sodium thio-sulphate until the solution 

 changes from the dirty and dark yellow solution to a bright lemon 

 yellow; or an excess of sodium thio-sulphate may be added and the 

 excess titrated with 1/20 normal iodide solution until the color 

 changes from the bright yellow of the lead iodide present to the 

 dirty and dark yellow. The number of cc. of sodium thio-sulphate 

 used, multiplied by 0.5175, will give the percentage of lead. Where 

 speed is not desirable the lead may be determined by adding sul- 

 phuric acid to the filtrate from the oxide of tin, or the lead and cop- 

 per may be deposited with the electric current. 



Dilute the filtrate from the lead peroxide to 500 cc, heat to 

 boiling and add 50 cc. of a 20$ sodium thio-sulphate solution, boil 

 five minutes, filter, wash with hot water, burn and weigh as CuO. 



Copper may also be determined as in the following method. 



♦Journal American Chemical Society. June. 1903. 



