Manual of qualitative analysis / by Robert Galloway.

  • Galloway, Robert.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: Manual of qualitative analysis / by Robert Galloway. Source: Wellcome Collection.

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    which we have detected, no other substance can be present, we must know not only the behaviour of the different sub- stances we are to look for with the reagents we shall employ, but we must know also the order and succession in which the reagents are to be applied. 84. It would be very difficult, if not impossible, to examine a solution for all the bases, if we were obliged to precipitate them singly from the solution, because it would be impossible to meet with, for each base, a reagent that would only precipitate that base and no other. For this and other reasons we divide the bases into families or groups; the acids are also divided into groups, but their division is more imperfect than that of the bases. The separation into groups is effected by observing some pro- perty common to several substances and peculiar to them, by which means a group is formed possessing distinctive characteristics, which distinguish its members from the lower groups. Most important advantages are gained by a distribution of this kind, as it would be impossible to analyse complex substances accurately without some such division ; for as many of the reagents precipitate more than one sub- stance, it would be difficult to decide in such cases what the particular substances. were which had been precipitated, and whether they had all been detected. Another impor- tant advantage arising from this arrangement is, that it is as easy to discover a group as an individual substance ; and the absence of a group being proved, it is unnecessary to examine further for any member contained in it. 85. We have divided the bases into the following six groups :—