GENERAL METHODS 



Special Tests for Free HC1. Perform the following tests on the 

 solutions as outlined above and tabulate the results. 



1. Gunzberg's Reagent. 1 Place 1 to 2 drops of the reagent in a 

 small porcelain evaporating dish and carefully evaporate to dryness 

 over a low flame. Insert a glass stirring rod into the mixture to be 

 tested and draw the moist end of the rod through the dried reagent. 

 Warm again gently and note the production of a purplish-red color 

 in the presence of free hydrochloric acid. 



2. Boas' Reagent. 2 Perform this test in the same manner as 1, 

 above. Free hydrochloric acid is indicated by the production of a 

 rose-red color which becomes less pronounced on cooling. 



3. Tropaeolin OO. 3 



(C 6 H 5 )NH - C 6 H 4 - N = N - 



- SO 3 Na. 



Place 2 drops of the solution to be tested and 1 drop of the indi- 

 cator in an evaporating dish and evaporate to dryness over a low 

 flame. The formation of a reddish-violet color indicates free 

 hydrochloric acid. 



This test may also be conducted in the same manner as 1, above. 



1 Giinzberg's reagent is prepared by dissolving 2 gms. of phloroplucinol 

 and 1 gm. of vanillin in 100 c.c. of 95 per cent alcohol. 



J Boas' reagent is prepared by dissolving 5 gms. of resorcinol and 3 gms. 

 of sucrose in 100 c.c. of 50 per cent alcohol. 



3 Prepared by dissolving 0.05 gm. of tropaeolin 00 in 100 c.c. of 50 per 

 cent alcohol. 



