6 UNIVERSITY OF COLORADO 



In actual practice these solutions are made to read 1 cc.=.005, 

 so that the reading will be direct on £ gram of ore or slag. 



Impurities in the chemicals, even in the so-called C.P., as well 

 as dust and organic matter (sometimes in the water, obtained by 

 the condensation of boiler steam, and due to the use of organic 

 boiler compounds), generally affect the solutions more or less, 

 hence it is well to let them stand a few days before using. 



In actual practice these solutions are always made up in quan- 

 tities of not less than four litres, and in duplicate, one bottle being 

 in use while the other is standing. 



STANDARDIZING SOLUTIONS. 



1. Potassium Bichromate. — Weigh out on the analytical bal- 

 ance a piece of C.P. iron wire, approximately .200 gram; cut into 

 small pieces and place in a flat-bottomed flask; pour about 15 cc. 

 cone. C.P. HC1 and 15 cc. boiling distilled water on it, and heat on 

 the hot plate until dissolved. Dilute with 100 cc. H 2 0; boil, and 

 add 2 drops of stannous chloride solution, stirring vigorously. Re- 

 move from the heat, allow to cool, add 20 cc. of mercuric chloride 

 solution, stir well. The solution should now look white and silky, 

 from the presence of mercurous chloride, and is ready for titration. 



Fill the burette to the zero mark with the bichromate solution. 

 Place on a clean, dry spot-plate the solution of potassium ferro- 

 cyanide. Transfer the iron solution to the No. 2 beaker, washing 

 out with cold distilled water. Run in the bichromate from the 

 burette, slowly, testing from time to time a drop on the ferro- 

 cyanide solution. It will give a dark blue at first, shading off to 

 colorless, this being the end reaction. 



Read the number of cc.'s used, divide the weight of iron taken 

 by the number of cc.'s used, and the quotient will represent the 

 amount of iron in the ferrous condition which 1 cc. of the solution 

 is capable of oxidizing. 



This should be done in duplicate, and the results should check. 



2. Potassium Permanganate. — Three methods are in gen- 

 eral use — < 



(a) By iron wire. 



(b) By oxalic acid. 



(c) By ferrous ammonium sulphate. 



