Exercises in quantitative chemical analysis : with a short treatise on gas analysis / by W. Dittmar.

  • Dittmar, Wilhelm, 1833-1892.
Date:
1887
Catalogue details

Licence: Public Domain Mark

Credit: Exercises in quantitative chemical analysis : with a short treatise on gas analysis / by W. Dittmar. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    32/340 (page 16)
    EXERCISES IN ANALYTICAL METHODS. Ex. 11.—Determination of Filter Ashes. In quantitative analysis, it is best to make a rule of using only Swedish paper, .as this gives less ash per square unit than any other filter paper in commerce (except the ash-free filters lately introduced by Schleicher and Schiill). But, in any case, before using a filter paper, the exact amount of ash which it contains must be determined as follows:— Cut out a stock of filters of the several sizes required in analysis. We are in the habit of naming the sizes by the length of their radii in centimetres, and speak of a No. 2, 3, 4, 4|,. 5 filter when we mean a filter of 2, 3, 4, 4J, or 5 centimetres radius respectively. Take, say, three No. 8 filters, fold and roll them up tightly into a small parcel, and, after having wound the end of a platinum wire round it, kindle it, and let it burn itself out completely, over a porcelain plate placed beneath it to catch any particles. Put the ash into a small, clean, platinum crucible, burn off the charcoal completely, allow to cool, weigh the whole, remove the ash (by means of a feather if necessary), and weigh the empty crucible. The difference gives the weight of the ash. Supposing it amounts to n mgs., we have, for the ash yielded by a filter of r centimetres radius, the formula— Ash in mgrs. = ^^Ajt x = Calculate k ^ 3x8^ Multiply h successively by the squares of the radii of the several sizes, and enter the results in a table. As treatment with acids removes a large proportion of the ash of a paper, repeat the determination with three No. 8 filters which have been previously