32 UNIVERSITY OF COLORADO 



SILVER DETERMINATION ON ANODE COPPER BY FIRE 



ASSAY. 



The silver is ppt. as AgCl, scorified and cupelled. 



Weigh 1 A.T. of the sample in duplicate, place in a large 

 beaker, add 200 cc. cold water + 130 cc. HN0 3 and let stand until 

 completely dissolved. Then add 175 cc. of cold water and 8 cc. 

 NaCl sol. (1 cc. equals 18.4 mgs.). Stir the solution well for a few 

 minutes and allow to stand for twelve hours, to allow AgCl to set- 

 tle. Filter and wash, add a couple of grams of litharge and set the 

 filter paper on a 2^-inch scorifier, place in a muffle and burn off the 

 filter paper at a very low temperature. Take the scorifier from the 

 muffle and add about 35 grams of lead with four grams of borax 

 for a cover. Place the scorifier in the muffle at a cherry red heat 

 and scorify at a low temperature. This gives about an 18-gr. 

 button. Cupel and weigh. 



BISMUTH IN METALLIC COPPER, 



Dissolve 10 to 50 grams of the copper in HN0 3 and H 2 0. If 

 much insoluble matter is present, filter off and fuse it with Na 2 C0 3 . 

 Dissolve the fusion in HN0 3 and add to main solution. To the so- 

 lution in HN0 3 add Na 2 C0 3 until a slight permanent precipitate 

 is formed. All the Bi will be included in this ppt. Filter it from 

 the main solution, dissolve the ppt. from the filter with warm di- 

 lute HC1. Evaporate the HC1 solution on a water bath till free 

 acid is driven off, then add five or six drops acid and 2 or 3 cc. of 

 water. The solution should be clear — if not, add a few drops HC1 

 to clarify, then pour into the solution a large volume of water (400 

 to 500 cc), and let the ppt. of BiOCl separate over night. Weigh 

 as BiOCl on Gooch crucible. 



ARSENIC AND ANTIMONY.* 



USED ON COPPER SMELTER FLUE DUSTS. j- 



To 1 gram of ore in a 3-inch casserole add 10 cc. HN0 3 and 

 warm. After the evolution of red fumes has nearly ceased, add 

 about 10 cc. H 2 S0 4 and run down to copious fumes of H 2 S0 4 . Do 



*By Lewis B. Skinner and R. H. Hawley, Colorado Springs, Colorado, 

 t But works equally well on ores, etc. 



