A systematic handbook of volumetric analysis, or, The quantitative estimation of chemical substances by measure, applied to liquids, solids, and gases : adapted to the requirements of pure chemical research, pathological chemistry, pharmacy, metallurgy, manufacturing chemistry, photography, etc., and for the valuation of substances used in commerce, agriculture and the arts / by Francis Sutton.

  • Sutton, Francis, 1831-1917.
Date:
1882
Catalogue details

Licence: Public Domain Mark

Credit: A systematic handbook of volumetric analysis, or, The quantitative estimation of chemical substances by measure, applied to liquids, solids, and gases : adapted to the requirements of pure chemical research, pathological chemistry, pharmacy, metallurgy, manufacturing chemistry, photography, etc., and for the valuation of substances used in commerce, agriculture and the arts / by Francis Sutton. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

    63/508 (page 47)
    TECHNICAL EXAMINATION OF COMMERCIAL ALKALINE COMPOUNDS. 6. Soda Ash, Black Ash, Mother-liciuors, &c. In refined alkali, moisture is determined by heating 5 or 10 gra. to dull redness for ten minutes, in a small crucible of platinum/silver, iron, or porce- lain, and allowing it to cool under a bell glass in the presence of sulphuric acid or calcic chloride: the difference between the first and second weighings is the accidental moisture in the sample. The contents of the crucible are then dissolved in about 150 c.c. of warm distilled water, and any insoluble matter filtered off by a small filter, washed on the latter a few times with hot water, then, if necessary, dried, ignited, and weighed as insoluble matter. It is important that tbis insoluble matter be removed before titration, otherwise the lime and other constituents in it will consume a portion of the normal acid, and so register a higher percentage of alkali than is really present. The total quantity of alkali is determined in a measured portion of the filtrate and washings, previously diluted to i or 1 liter, by normal sulphuric, nitric, or oxalic acid, as in § 16.1.* The quantity of caustic alkali present in any sample is determined as in § 16. 2. A custom prevails in the soda trade of calculating the atomic weight of sodium as 24 instead of 2.3, thus representing more real soda present in a sample of alkali than actually exists; this practi- cally leads to an error of from 1 to 2 per cent, in a 50-per-cent. ash, according to the method of calculation. This anomaly ought to he got rid of, and one uniform standard adopted. The presence of sulphides is ascertained b}^ the smell of sulphuretted hydrogen when the alkali is saturated with an acid, or by dipping paper steeped in sodic nitro-prusside into the solution; if the paper turns blue or violet, sulphide is present. The quantity of sulphide and hyposulphite may be determined by saturat- ing a dilute solution of the alkali with a slight excess of acetic acid, adding starch liquor, and titrating with decinormal iodine solution till the blue colour appears. The quantity of iodine required is the measure of the sulphiiretted hydrogen and hyposulphurous acid present. The quantity of each may be known by adding a solution of sulphate of zinc to a like quantity of the alkali, and filtering so as to remove the free carbonated and sulphur- etted alkali, by which means the hyposulphurous acid alone remains, which may be estimated with iodine and starch as before; the quantity of iodine solution so required is to be deducted from the total, and the calculation for both sulphide and hyposulphite of sodium may then be made, 1 c.c. iodine is equal to 0'0248 gm. hyposulphite, or 0'0039 gm. sodic sulphide; good English alkali is seldom contaminated with these substances to any extent. Sodic chloride (common salt) may be determined by neuti-alizing 0585 gm. or 5'85 gm. of the alkali with nitric acid, and titrating with decinormal * This gives a slight error, owing to traces of alvimiuato of soda and lime, which consume acid.