Part 11

Table 8.—RELATIONS BETWEEN ALKALINITY TO PHENOLPHTHALEIN AND THAT TO METHYL ORANGE, ERYTHROSINE, OR LACMOID, IN PRESENCE OF BICARBONATE, CARBONATE, AND HYDROXIDE.

─────────────────┬───────────────────────────────────────────────────── Result of │ Value of radicle expressed in terms of calcium titration. │ carbonate. ─────────────────┼─────────────────┬─────────────────┬───────────────── │ Bicarbonate. │ Carbonate. │ Hydroxide. ─────────────────┼─────────────────┼─────────────────┼───────────────── P = 0 │ T │ 0 │ 0 P < 1/2T │ T − 2P │ 2P │ 0 P = 1/2T │ 0 │ 2P │ 0 P > 1/2T │ 0 │ 2(T − P) │ 2P − T P = T │ 0 │ 0 │ T ─────────────────┴─────────────────┴─────────────────┴─────────────────

Footnote C:

T = Total alkalinity in presence of methyl orange, erythrosine, or lacmoid. P = Alkalinity in presence of phenolphthalein.

Reagents.—1. Sulfuric acid or potassium bisulfate. A N/50 solution.

2. Phenolphthalein indicator. Dissolve 5 grams of a good quality of phenolphthalein in 1 liter of 50 per cent alcohol. Neutralize with N/10 potassium hydroxide. The alcohol should be diluted with boiled distilled water.

3. Methyl orange indicator. Dissolve 0.5 gram of a good grade of methyl orange in 1 liter of distilled water. Keep the solution in the dark.

4. Lacmoid indicator. Dissolve 2.0 grams of lacmoid in 1 liter of 50 per cent alcohol. Dilute the alcohol with freshly boiled distilled water.

5. Erythrosine indicator. Dissolve 0.5 gram of erythrosine (the sodium salt) in 1 liter of freshly boiled distilled water.

PROCEDURE WITH PHENOLPHTHALEIN.

Add 4 drops of phenolphthalein indicator to 50 or 100 cc. of the sample in a white porcelain casserole or an Erlenmeyer flask over a white surface. If the solution becomes colored, hydroxide or normal carbonate is present. Add N/50 sulfuric acid from a burette until the coloration disappears.

The phenolphthalein alkalinity in parts per million of calcium carbonate is equal to the number of cubic centimeters of N/50 sulfuric acid used multiplied by 20 if 50 cc. of the sample was used, or by 10 if 100 cc. was used.

PROCEDURE WITH METHYL ORANGE.

Add 2 drops of methyl orange indicator to 50 or 100 cc. of the sample, or to the solution to which phenolphthalein has been added, in a white porcelain casserole or an Erlenmeyer flask over a white surface. If the solution becomes yellow, hydroxide, normal carbonate, or bicarbonate is present. Add N/50 sulfuric acid from a burette until the faintest pink coloration appears. The methyl orange alkalinity in parts per million of calcium carbonate is equal to the total number of cubic centimeters of N/50 sulfuric acid used multiplied by 20 if 50 cc. of the sample was used, or by 10 if 100 cc. was used.

PROCEDURE WITH LACMOID.

Add 4 drops of lacmoid indicator to 50 or 100 cc. of the sample in a porcelain casserole or an Erlenmeyer flask. Add N/50 sulfuric acid from a burette until within 1 or 2 cc. of the amount necessary for neutralization has been added. Heat the solution until bubbles of steam begin to break at the surface. Remove the dish from the source of heat and continue the titration until a drop of the acid striking the surface of the liquid and sinking to the bottom of the vessel produces no change in the uniform reddish or purple color of the solution. The calculation is the same as for phenolphthalein alkalinity.

PROCEDURE WITH ERYTHROSINE.

Add 5 cc. of neutral chloroform and 1 cc. of erythrosine indicator to 50 or 100 cc. of the sample in a 250 cc. clear glass-stoppered bottle. If the chloroform becomes rose colored on shaking, hydroxide, bicarbonate, or normal carbonate is present. Add N/50 sulfuric acid from a burette until the chloroform becomes colorless. A white surface behind the bottle facilitates detection of a trace of color as the end-point is approached. The calculation is the same as with phenolphthalein alkalinity.

BICARBONATE.

Bicarbonate is present if the alkalinity to phenolphthalein is less than one-half the alkalinity to methyl orange, erythrosine, or lacmoid. The alkalinity to methyl orange, erythrosine, or lacmoid is due entirely to bicarbonate if there is no phenolphthalein alkalinity. If there is phenolphthalein alkalinity the bicarbonate, in terms of calcium carbonate, is equal to the methyl orange, erythrosine, or lacmoid alkalinity minus twice the phenolphthalein alkalinity. Bicarbonate, carbon dioxide as bicarbonate, and half-bound carbon dioxide can be calculated as follows:

Bicarbonate (HCO_{3}) = 1.22 times the bicarbonate expressed in terms of calcium carbonate.

Carbon dioxide (CO_{2}) as bicarbonate = 0.88 times the bicarbonate expressed in terms of calcium carbonate.

Half-bound carbon dioxide (CO_{2}) = 0.44 times the bicarbonate expressed in terms of calcium carbonate.

NORMAL CARBONATE.

Normal carbonate is present if the alkalinity to phenolphthalein is greater than zero but less than the alkalinity to methyl orange, erythrosine, or lacmoid. If the phenolphthalein alkalinity is exactly equal to one-half the methyl orange, erythrosine, or lacmoid alkalinity the alkalinity is due entirely to normal carbonate. If the phenolphthalein alkalinity is less than one-half the methyl orange, erythrosine, or lacmoid alkalinity normal carbonate expressed in terms of calcium carbonate is equal to twice the phenolphthalein alkalinity. If the phenolphthalein alkalinity is greater than one-half the methyl orange, erythrosine, or lacmoid alkalinity the normal carbonate is equal to twice the difference between the methyl orange, erythrosine, or lacmoid alkalinity and the phenolphthalein alkalinity. The carbonate, carbon dioxide as carbonate, and bound carbon dioxide can be calculated as follows:

Carbonate (CO_{3}) = 0.6 times the normal carbonate expressed in terms of calcium carbonate.

Carbon dioxide as carbonate (CO_{2}) = 0.44 times the normal carbonate expressed in terms of calcium carbonate.

Bound carbon dioxide (CO_{2}) is the sum of the carbon dioxide as carbonate and one-half that as bicarbonate.