QUALITATIVE AND QUANTITATIVE ANALYSIS 57 



Thomas' Reagent for Ammonia 



Prepare a 5 per cent solution of phenol and a sodium hypochlo- 

 rite solution containing 1 per cent available chlorine: 1 cubic 

 centimeter of the NaOCl solution will neutraHze 2.86 cubic 

 centimeters of O.IN sodium thiosulphate. 



Dilute the culture, 0.2 to 1.0 cubic centimeter with 8 cubic 

 centimeters of water and add 1 cubic centimeter of phenol and 

 1 cubic centimeter of hypochlorite. Let stand for J^ hour. A 

 blue color indicates ammonia or amines. 



Trommsdorf's Reagent for Nitrites 



1. Add slowly, with constant stirring, a boiling solution of 20 

 grams of zinc chloride in 100 cubic centimeters of distilled water 

 to a mixture of 4 grams of starch in water. Continue heating 

 until the starch is dissolved as much as possible, and the solution 

 is nearly clear. 



2. Then dilute with water and add 2 grams zinc iodide. 



3. Dilute to 1 Hter and filter. 



4. Store in well-stoppered bottles in the dark. 



Test for Nitrites. — Place 3 drops of Trommsdorf's reagent 

 in depression on test plate. Add 1 drop of dilute sulphuric acid 

 (1:3). Remove a loopful of the solution to be tested and touch 

 to surface of reagent. A blue color indicates the presence of 

 nitrites. 



Reagents for Nitrate, Nitrite, and Hydroxylamine 



(a) Dissolve 10.5 grams sulfanilic acid and 6.8 grams sodium 

 acetate in 1,000 cubic centimeters of 30 per cent (by volume) 

 acetic acid, by heating on water bath. Boil for 3 minutes and 

 make up to 1,000 cc. 



(b) Boil 5 grams a-naphthylamine in 700 cubic centimeters of 

 water for 5 minutes, then filter and add 5 cc. of concentrated 

 HCl, cool and make up to 1,000 cc. 



Solutions (a) and (h) are always kept separate. 



(c) Dissolve 1.3 grams iodine in 100 cubic centimeters of glacial 

 acetic acid. 



{d) Dissolve 2.5 grams Na2S203-5H20 in 100 cubic centi- 

 meters of water. 



