4. A 10 per cent. solution of barium chloride. Preparation: 100 grams of barium chloride are dissolved in one liter of distilled water and filtered. The neutrality of the solution should be proven as it must be neutral.
5. α naphtholphthalein indicator according to Sorenson. Preparation: 0.1 gram of α naphtholphthalein is dissolved in 150 cubic centimeters of alcohol and 100 cubic centimeters of water. For every 10 cubic centimeters of liquid use at least 12 drops of indicator.
6. Phenolphthalein solution 1 gram to 100 cubic centimeter 96 per cent. alcohol.
7. Solvent, 50 per cent. alcohol neutralized.
MANIPULATION.
First—Determine the strength of the N/10 alcoholic sodium hydroxide in terms of N/10 hydrochloric acid and calculate the factor, e. g.:
| 10 c.c. N/10 alcoholic NaOH | = 9.95 N/10 HCl} | 9.96 |
| 10 c.c. N/10 alcoholic NaOH | = 9.96 N/10 HCl} |
The alcoholic N/10 NaOH has a factor of 0.996.
Second—Control the N/40 stearic acid with the above alkali to obtain its factor, e. g.:
| 40 c.c. N/40 alcoholic stearic acid = | 10.18 c.c. N/10 NaOH } | } 10.2 |
| 40 c.c. N/40 alcoholic stearic acid = | 10.22 c.c. N/10 NaOH } |