1. What effect would addition of water to vinegar have upon its specific gravity? 2. What effect would addition of such material as sugar have upon specific gravity? 3. Why should the specific gravity of vinegar be fairly constant? 4. What would be the weight of 1000 cc. of vinegar calculated from the specific gravity?
Experiment No. 36
Acidity of Vinegar
Into a small beaker pour 6 cc. of vinegar and 10 cc. of water and a few drops of phenolphthalein indicator. Run in standard KOH solution from a burette until a faint pink tinge remains permanently. Note the number of cubic centimeters of KOH solution required to neutralize the acid. Divide this number by 10, which will give approximately the per cent of acetic acid.
1. How may the per cent of acidity of vinegar be determined? 2. Why was phenolphthalein used? 3. Why was KOH used? 4. What acids does vinegar contain? 5. What is the legal requirement in this state for acetic acid in vinegar? 6. How did the acidity you obtained compare with this legal requirement?
Experiment No. 37
Deportment of Vinegar with Reagents
To 10 cc. of vinegar in a test tube add 8 or 10 drops of lead sub-acetate and shake. Observe the precipitate. Lead sub-acetate precipitates mainly the malic acid which is always present in cider vinegar.
1. How may the presence of malic acid in a vinegar be detected? 2. Describe the precipitate. 3. What does malic acid in a vinegar indicate?