SECTION IX 



PREPARATION OF REAGENTS AND QUALITATIVE METHODS 

 OF ANALYSIS 



Pyrogallic Acid for Absorbing Oxygen. For every 100 

 c.c. of air space take i gram of pyrogallic acid and 10 

 c.c. of a 10 per cent, solution of sodium or potassium 

 hydroxid. 



Note. To Prepare an Anaerobic Jar. Cover the bottom of an anaerobic 

 jar with ^-inch layer of pyrogallic acid. Fit the cover tightly to the jar 

 with vaselin and draw out the air with a suction-pump, and when there is 

 a good vacuum, run in 75 to 100 c.c. alkali. 



(1) Phenolphthalein : 



Phenolphthalein 10 gm. 



Alcohol (86 per cent.) 1000 c.c. 



Dissolve the phenolphthalein in the alcohol and neu- 

 tralize with sodium hydroxid until faintly pink. 



(2) Methyl-orange: 



Methyl-orange 0.2 gm. 



Distilled water 1000.0 c.c. 



Dissolve the solid methyl-orange in hot water, allow to 

 cool, and if a deposit forms, filter. If the sodium salt is 

 used instead of the acid, take 0.22 gram to i liter of water. 

 Add 0.67 c.c. of normal hydrochloric acid, let stand, and 

 filter. 



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