APPENDIX 



DIRECTIONS FOR MAKING UP QUANTITATIVE 

 OR SPECIAL REAGENTS 



Ammonium Thiocyanate, Standard, for Chlorides. 



One c.c. is equivalent to 1 c.c. standard AgN0 3 . 



This solution is made of such a strength that 1 c.c. of it 

 is equal to 1 c.c. of the standard silver nitrate solution men- 

 tioned below. To prepare the solution dissolve 12.9 grams 

 of ammonium thiocyanate, NH 4 SCN, in a little less than a 

 liter of water. In a small flask place 20 c.c. of the standard 

 silver nitrate solution, 5 c.c. of a cold saturated solution of 

 ferric alum and 4 c.c. of nitric acid (sp. gr. 1.2), add water 

 to make the total volume 100 c.c., and thoroughly mix the 

 contents of the flask. Now run in the ammonium thiocyanate 

 solution from a burette until a permanent red-brown tinge 

 is produced. This is the end-reaction and indicates that the 

 last trace of silver nitrate has been precipitated. Take the 

 burette reading and calculate the amount of water neces- 

 sary to use in diluting the ammonium thiocyanate in order 

 that 10 c.c. of this solution may be exactly equal to 10 c.c. 

 of the silver nitrate solution. Make the dilution and titrate 

 again to be certain that the solution is of the proper strength. 



Barfoed's Solution. 



Dissolve 4.5 grams of neutral, crystallized copper acetate 

 in 100 c.c. of water and add 1.2 c.c. of 50% acetic acid. 



Barium Chloride for Sulphate Determination. 



Thirty and five-tenths grams BaCl 2 . 2H 2 made up to 1 liter 

 with distilled water. 



One c.c. corresponds to 0.01 grams S0 3 . 



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