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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    98. How 1T0 ASCERTAIN THE PRESENCE OR ABSENCE OF BACH OF THE THREE MEMBERS OF THIS GROUP IN A SOLU- TION WHICH CAN ONLY CONTAIN THESE THREE BASES.—As the presence of ammonia interferes, as before stated, with the detection of potash, we are always obliged, on this ac- count, to look for ammonia before we look for potash. And as the reagent we add for the detection of ammonia would inter- fere (A 2) with the detection of the two other members of the group, we are obliged, on this account, to look for the ammonia in a portion only of the solution under examination. For these reasons, then, we divide the solution into two parts, which we shall call A and B. 99. In A we examine for AMMONIA according to the method described in A 2 and paragraph 106. The method there described is the characteristic test for ammonia; in that way it can be distinguished from all other substances. As the absence or presence of ammonia regulates our mode of search for the two other members of the group, we must describe the mode of proceeding to be adopted when it is absent, as well as when it is present. 100. If wz is absent, the B portion of the solution is examined for soda and potash in the following way :— a clean (see Precautions, paragraph 103) platinum wire is dipped into the solution, and then exposed to the inner blowpipe flame: if the flame is coloured yellow, sopa is present ; if it is coloured violet, it proves the absence of soda (C 4) and the probable presence of porasu (B 4). Lf soda is present, examine for potash by Cartmell’s photo- chemical method (paragraph 112). The presence of potash may be confirmed by adding to the solution under exami- nation, which must be cold (B 8), a solution of tartaric acid or bitartrate of soda (see paragraph 110) in excess, and shaking the mixed liquid very violently, and then allowing