Public Health Papers and Reports Volume 30, PT. 2 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1905 Excerpt: ...phenolphthalein as the indicator, using the glass stirrer and observing the same precautions as in the Sehler method for the determination of free carbonic acid. Owing to the effect of temperature upon the solubility of calcium oxide, it has been found to be necessary to make a blank determination with distilled water and lime water. It is clear that in this blank determination the procedure must be identical with that used for the water, and that great care must be exercised to avoid carbonation of the lime water through exposure to the air. Twice the difference between the number of c.c. of jy sulphuric acid required to neutralize 100 c.c. of the lime water blank, and the number of c.c. of 0 sulphuric acid required to neutralize the excess of lime in 100 c.c. of the sample, is an expression, in terms of sulphuric acid, for the amount of magnesium present in 100 c.c. of the water under examination. The following formula is convenient for calculating the amount of magnesium in parts per million. Let S = Number of c.c. of H, S04 required to neutralize 100 c.c. of the lime water blank. Let N = Number of c.c. of j H, S04 required to neutralize the excess of calcium oxide in 100 c.c. of the mixture of lime water and of hard water. Then Magnesium (Mg) Parts per million = 2.4 (2S-2N). The method gives very satisfactory results provided that the precautions mentioned above are rigidly observed. The change in the strength of the lime water during the heating involved in this method is illustrated by the following example of an analysis: Strength of Lime Water (Available CaO). Parts per million. Lime Water Blank. Before Heating After Heating 974 896 Analysis. Formula: Mg = 2.4 (2S-2N). = 2.4 (40i-8) therefore S = 20 N = 9 =53 parts per million. A gravimetric a...