60 UNIVERSITY OF COLORADO 



HN0 3 , boil a few minutes, and then ppt. with ammonia and filter 

 to separate most of the zinc, dissolve the ppt. in hot HN0 3 and ppt. 

 the phosphorus with molybdate solution. The yellow ppt. may be 

 weighed or titrated. 



BEARING METALS. 



If the sample is high in tin and low in lead, proceed as outlined 

 for bronzes; but if the sample is high in lead and contains anti- 

 mony, proceed as suggested by Mr. George Hopkins, chemist to the 

 Carrie Furnaces of the Homestead Steel Works, he having found 

 that the addition of an excess of pure tin will insure the complete 

 separation of the antimony with the oxide of tin. Weigh 0.5 gram 

 of the sample and £ gram of pure tin into a tall No. 2 beaker, 

 cover with a watch-glass, add 20 cc. HN0 3 (Sp. Gr. 1.33) and boil 

 down to a pastiness, add 40 cc. hot H 2 and boil a few minutes, 

 filter and wash with a 2$ HN0 3 , burn and weigh as Sn0 2 +Sb 2 4 . 

 The filtrate is made strongly alkaline with caustic potash and the 

 lead oxidized by adding about 10 grams ammonium persulphate. 

 The rest of the analysis is carried out as outlined for bronzes. 



To determine the antimony, weigh 1 gram of the sample and 

 1 gram KI into a No. 2 beaker, add 80 cc. HC1 (Sp. Gr. 1.10) and 

 boil gently for one hour, filter on a weighed paper or Gooch cru- 

 cible and wash with dilute HC1, and then with hot H 2 until free 

 from chlorides. Wash once with alcohol, dry for one hour at 100° 

 C. and weigh. The increase in weight is metallic antimony. Cal- 

 culate this to Sb 2 4 and subtract from the weight of the mixed 

 oxides; calculate the tin from the weight of the stannic oxide 

 found and subtract the tin which was added. 



Arsenic is determined in a separate portion by any of the well- 

 known distillation methods. 



Bismuth, if present, would be found with the copper sulphide, 

 and can be determined by dissolving the copper sulphides in HN0 3 , 

 and ppting. the bismuth with ammonia. 



