Testing Baking Powders for Ammonia
Dissolve ½ gm. of material in 10 cc. water; filter off any insoluble residue and to the filtrate add 2 or 3 cc. NaOH and apply heat. Test the gas given off with moistened turmeric paper. If NH3 is present, the paper will be colored brown. Do not allow the paper to come in contact with the liquid or sides of the test tube. (Perform the tests on two samples of baking powder.)
1. How do you test a baking powder for ammonia? 2. Why do you add NaOH? 3. Why must you be careful not to let the turmeric paper touch the sides of the test tube or the liquid?
Experiment No. 34
Vinegar Solids
Into a weighed aluminum or porcelain dish pour 10 cc. of vinegar. Weigh and then evaporate over boiling water. To drive off the last traces of moisture dry in the water oven for an hour. Cool and weigh. Calculate the per cent of solids. Observe the appearance of the solids. Test both samples and compare.
1. How may the per cent of solids in vinegar be determined? 2. Describe the appearance of the solids from the good and from the poor sample of vinegar. 3. What is the legal standard for vinegar solids in your state?
Experiment No. 35
Specific Gravity of Vinegar
Pour 170 cc. vinegar into 200 cc. cylinder. Place a hydrometer for heavy liquids (sp. gr. 1 to 1.1) in the cylinder. Note the depth to which it sinks and the point registered on the scale on the stem. Note temperature of vinegar. Record specific gravity of vinegar.