Identification of Group V cations

17 IDENTIFICATION OF GROUP V CATIONS The Group V cations (Mg2+, Na+, K+, and NH4) can be identified one by one without preliminary 

If the residue dissolves completely (or almost completely) in water, dilute the resulting solution (after filtration, if necessary) to about 6 ml and divide it into three approximately equal parts (i) Use the major portion to test for Mg with the prepared oxine solution confirm Mg by applying the mageson test to 3-4 drops of the solution (ii) and (iii) Test for Na and K, respectively, as described below. 

Dissolve in a few drops of dilute HC1 and add 2-3 ml water. Divide the solution into two unequal parts. 

Confirm by flame test persistent yellow flame. 

Confirm by flame test and view through two thicknesses of cobalt glass red colouration (usually transient). 

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Table V.28 Identification of Group V cations Treat the dry residue from Group IV with 4 ml water, stir, warm for 1 minute and filter (1).

VI.16 IDENTIFICATION OF GROUP V CATIONS ON THE SEMIMICRO SCALE Apart from a partial separation of magnesium, it is not possible to separate the Group V cations from one another it is however simple to carry out individual tests for each of them. As we have used ammonia and ammonium salts in the previous separations, we cannot test for ammonium ions in the... 

Table VI.19 Identification of Group V cations on the semimicro scale Treat the dry residue (contained in a small crucible) with 1 ml water, stir for 1 minute, and transfer with the aid of a further 05 ml water to a semimicro centrifuge tube. Centrifuge. (1)...

Table V.13 Separation and identification of Group I cations (silver group) The ppt. may contain PbCl2, AgCl, and Hg2Cl3. Wash the ppt. on the filter first with 2 ml of 2m HC1, then 2-3 times with 1 ml portions of cold water and reject the washings with water. Transfer the ppt. to a small beaker or to a boiling tube, and boil with 5-10 ml water. Filter hot. (1)...

VL11 SEPARATION OF GROUPS IIA AND IIB AND SEPARATION AND IDENTIFICATION OF GROUP IIA CATIONS When describing these separations in macro scale, two alternative methods have been suggested (see Section V.10), one being based on the use of ammonium polysulphide (see Table V.14) and the other on potassium hydroxide (Table V.15). In semimicro scale the potassium hydroxide method is more suitable and this will be presented here. This does not mean however that the ammonium polysulphide... 

VI.12 SEPARATION AND IDENTIFICATION OF GROUP IIB CATIONS ON THE SEMIMICRO SCALE For this separation the centrifugate from Group IIA is used. The separation scheme outlined in Table VI. 14 is therefore linked directly to Table VI in Section VI.11. If the ammonium polysulphide method has been adopted for the separation of Groups IIA and IIB, the student should scale down the scheme given in Table V.18 (Section V.12) to semimicro scale. 

VI.14 SEPARATION AND IDENTIFICATION OF GROUP IIIB CATIONS ON THE SEMIMICRO SCALE The separation scheme outlined in Table VI. 16 commences with the sulphide precipitates obtained according to the prescriptions of the general separation table (Table VI. 11 in Section VI.9). It is a semimicro adaptation of the hydrochloric acid-hydrogen peroxide method, described in Table V.24 (Section V.15). 

For further explanations consult the notes to Table V.14 in Section V.10. For the separation and identification of Group IIA cations, follow Table VII.3. ... 

The uncertainty concerning the identification of the stabilization mechanism on polar ZnO surfaces is partly due to the lack of atomically resolved STM images. Such images are possible for the nonpolar (1010) and (1120) surfaces [40,41] but have, to our knowledge, not been reported for polar surfaces. The polar cation terminated (111) surface of zincblende compounds typically displays a 2 x 2 reconstruction associated with removal of every fourth surface cation [43,50-52]. This structure is ideally suited to match the charging condition for surface stabilization for this particular surface orientation. The 2x2 reconstruction and the missing surface atoms can directly be observed by STM [52]. In contrast to literature [53], a 2 x 2 reconstruction is also frequently observed in our group for the (0001) surface of wurtzite CdS.4 The reconstruction on the anion terminated (III) surfaces of III—V and II-VI zincblende compounds are considerably more complex. These surfaces... 

V.9 SEPARATION AND IDENTIFICATION OF THE GROUP I CATIONS (SILVER GROUP) The residue after filtering off the precipitate obtained with dilute hydrochloric acid (cf. Table V.12 in Section V.8) may contain lead, silver, and mercury ions. Their separation and identification can be carried out according to the scheme shown in Table V. 13. 

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