[311] ‹Cf.› p. 136, concerning precautions used to prevent precipitates from assuming the ‹colloidal› state.
[312] Fresenius, ‹Quantitative Analysis›, I, 355 (1904).
[314] Official Methods of Analysis, Bulletin 107, p. 11, U. S. Dept. of Agriculture.
[315] The excess of chloroplatinic acid is first washed out of the precipitate primarily to avoid subsequent precipitation of ammonium chloroplatinate, but its removal also avoids the error discussed in the text.
[317] Mulder. See Sutton's ‹Volumetric Analysis›, p. 304 (1904).
[319] A table of exact solubilities is given at the end of the Lab. Manual, ‹q.v.›
[320] In the most exact quantitative work, as demanded in the determinations of atomic weights, every known loss must, as far as possible, be measured and taken into account. Beautiful instances of such work are found in T. W. Richards' classic determinations of atomic weights. See, for instance, Richards, ‹Carnegie Institution Publications›, No. 125 (1910), Determinations of the Atomic Weights of Silver, Lithium and Chlorine («Stud.»).
[321] ‹Z. Elektrochem.›, «11», 797 (1905).
[322] ‹Ibid.›, «11», 936 (1905), and «12», 725 (1906).
[323] ‹Z. phys. Chem.›, «55», 707 (1906), and «61», 638 (1907).
[324] If ‹n› is the number of moles of solute dissolved in ‹N› moles of solute, the concentration of the solute may be expressed as ‹n› / (‹n› + ‹N›), which is called its "mole fraction." This form of expressing concentrations is in many particulars preferable to the mole / liter form. For very dilute solutions (‹n› is very small compared with ‹N›) the two forms become practically identical, but they are not so for more concentrated solutions, and the ‹mole-fraction› expression is then easier to treat rigorously.
[325] See Walden, ‹loc cit.›, for more extended data.
«SYSTEMATIC ANALYSIS AND THE APPLICATION OF FUNDAMENTAL PRINCIPLES»
«SYSTEMATIC ANALYSIS FOR THE COMMON METAL IONS. THE IONS OF THE ALKALIES AND OF THE ALKALINE EARTHS. ORDER OF PRECIPITATION OF DIFFICULTLY SOLUBLE SALTS WITH A COMMON ION»
In systematic analysis it is most convenient to make separate examinations for the metal and for the acid ions. The examination for metal ions usually precedes that for the acid ions, and the scheme of analysis for the former will be considered first.