APPENDIX. 423 



Spiegler's Reagent. 1 This reagent has the following composi- 

 tion : 



% 



Tartaric acid 20 grams. 



Mercuric chloride 40 grams. 



Glycerol 100 grams. 



Distilled water 1000 grams. 



Standard Ammonium Thiocyanate Solution. 2 This solu- 

 tion is made of such a strength that I c.c. of it is equal to I c.c. of 

 the standard argentic nitrate solution mentioned below. To pre- 

 pare 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 argentic 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 thor- 

 oughly mix the contents of the flask. Now run in the ammonium 

 thiocyanate solution from a burette until a permanent brozvn 

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

 last trace of argentic nitrate has been precipitated. Take the burette 

 reading and calculate the amount of water necessary to use in dilut- 

 ing the ammonium thiocyanate in order that 10 c.c. of this solu- 

 tion may be exactly equal to 10 c.c. of the argentic nitrate solution. 

 Make the dilution and titrate again to be certain that the solution 

 is of the proper strength. 



Standard Argentic Nitrate Solution. 3 Dissolve 29.06 grams of 

 argentic nitrate in i liter of distilled water. Each cubic centimeter 

 of this solution is equivalent to o.oi gram of sodium, chloride or 

 to 0.006 gram of chlorine. 



Standard Uranium Acetate Solution. 4 Dissolve 35.461 grams 

 of uranium acetate in I liter of water. One c.c. of such a solution 

 should be equivalent to 0.005 g ram of P 2 O 5 , phosphoric anhydride. 



This solution may be standardized as follows : To 50 c.c. of a 

 standard solution of disodium hydrogen phosphate, of such a 

 strength that the 50 c.c. contains o.i gram of P 2 O 5 , add 5 c.c. of the 

 sodium acetate solution mentioned on p. 422 and titrate with the 

 uranium solution to the correct end-reaction as indicated in the 



1 Spiegler's ring test, pages 98 and 316. 



2 Volhard-Arnold method, page 396, and Clark's modification of Dehn's 

 method, page 394. 



s Volhard-Arnold method, page 396, Mohr's method, page 395, and Clark's 

 modification of Dehn's method, page 394. 

 4 Uranium acetate method, page 389. 



