BROMCRESOL GREEN-METHYL RED INDICATOR POWDER PILLOWS May cause eye, skin and
respiratory tract irritation. Do not ingest, inhale, or allow contact with skin or eyes. In case of
contact, immediately flush eyes and skin with water for 15 minutes. In case of ingestion,
immediately give large quantities of water. In case of inhalation, remove victim to fresh air. Call
medic in all cases.
Add the contents of one bromcresol green-methyl red indicator powder pillow(2) to the water sample in the
mixing bottle(5). Swirl to mix.
If the water turns either gray-blue, blue, or green the free acidity is zero. Then the test is complete. If the
water turns pink go to step (4).
SODIUM HYDROXIDE STANDARD SOLUTION Causes burns. Harmful if swallowed. Do not
ingest or allow contact with skin or eyes. In case of contact, immediately flush eyes and skin
with water for 15 minutes. Remove contaminated clothing. In case of ingestion, DO NOT induce
vomiting. Give large quantities of water. Give at least one ounce of vinegar in an equal amount
of water. Call medic in all cases.
If the water turns pink during step (3), add standard sodium hydroxide solution(l) drop by drop until the
water just begins to turn gray-blue. Count the drops as they are added. Record the number of drops.
Constantly swirl the mixing bottle(5) while adding the sodium hydroxide(l).
Interpretation of Results:
If the water is gray-blue, blue or green at the end of step (3), the free acidity is zero.
If not zero, the free acidity (in mg/l of calcium carbonate equivalents) is equal to 20 times the number of
drops of sodium hydroxide standard solution used.
If the results show that the free acidity is less than 150 mg/l, more accurate results may be obtained by
performing the Free Acidity Test, Low Range (para 22.214.171.124) on another test sample.
126.96.36.199. Free Acidity Test. Low Range.
Purpose of Test: To determine the total acidity in a water sample in terms of the amount of calcium carbonate
required to neutralize the sample.
Range: From 0 to 150 mg/l of calcium carbonate equivalents
Equipment Used: Found in Acidity Test Kit, para 2.6.3, fig. 2-7
Standard sodium hydroxide solution, (1), fig. 2-7
Bromcresol green-methyl red, (2), fig. 2-7
Test tube, (3), fig. 2-7
Mixing bottle, (5), fig. 2-7
General Techniques Used: Refer to paragraphs cited below as required by procedure.
Planning the Test, para 188.8.131.52
Cleaning Glassware, para 184.108.40.206
Handling and Storing Reagents, para 220.127.116.11
Collecting Water Samples, para 18.104.22.168
Mixing, para 22.214.171.124
Titrating, para 126.96.36.199
Collect water sample by filling the mixing bottle (5, fig. 2-7) up to the 23 ml mark with the water to be