III Chloride — Perchloric Acid Reagent

Dissolve 5 g iron(III) chloride hexahydrate in a mixture of 50 ml water and 50 ml perchloric acid (70%). 

The chromatogram is freed from mobile phase in a stream of warm air, immersed for 4 s in the dipping solution or sprayed evenly with the spray solution until just transparent, dried briefly in the air and then heated to 110—120 C for 20 — 60 min. 

Note Indoles, that are substituted with oxygen in position 2 or 3, do not react [11]. The reagent can be employed on silica gel, kieselguhr and Si 50 000 layers. Aluminium oxide layers are not suitable [3]. 

Danger warning Mists of perchloric acid can condense in the exhausts of fume cupboards and lead to uncontrolled explosions So dipping is to be preferred. 

Layer HPTLC plates Silica gel 60 (Merck). The layers were pre- 

---

Ironfim Chloride - Reaction Iron(III) Chloride — Perchloric Acid Reagent 315... 

In particular, sulphuric acid, molybdophosphoric acid, antimony(III)-chloride and fluorescence indicators and others quoted in Table 58 can be used for detection. Richter [142] has obtained blue colours with Zl - and zl -3j8-hydroxysterols in amounts down to 0.03 fig, using the naphthoquinonesulphonic acid-perchloric acid reagent. Reference may be made to Boliiger s chapter (K) for the vitamin D group to section XI on bile acids for bile alcohols (neutral C27-sterols) and to Mangohd s chapter (M) for separation of lipids, including cholesterol and its esters. 

Redox titrants (mainly in acetic acid) are bromine, iodine monochloride, chlorine dioxide, iodine (for Karl Fischer reagent based on a methanolic solution of iodine and S02 with pyridine, and the alternatives, methyl-Cellosolve instead of methanol, or sodium acetate instead of pyridine (see pp. 204-205), and other oxidants, mostly compounds of metals of high valency such as potassium permanganate, chromic acid, lead(IV) or mercury(II) acetate or cerium(IV) salts reductants include sodium dithionate, pyrocatechol and oxalic acid, and compounds of metals at low valency such as iron(II) perchlorate, tin(II) chloride, vanadyl acetate, arsenic(IV) or titanium(III) chloride and chromium(II) chloride. 

Fluorescamines Antimony (III) chloride (10% in chloroform) Benedict reagent Lead (IV) acetate (basic, 25%) p-Toluenesulfonic acid (20% in chloroform) Perchloric acid (70%)... 

Some of these effects are illustrated in the experimental curves of Figures 15-1 and 15-2. In the titration of Fe(II), before the end point the shapes are independent of the nature of the oxidant. The value of El is highest with perchloric acid, because hydrolysis of Fe(III) is largely suppressed and the perchlorate ion has little tendency to form complexes. With sulfuric acid and with Ce(IV) as titrant, the two effects of hydrolysis and complex formation tend to counteract each other. In the presence of phosphoric acid, complex formation predominates, and El is distinctly lower. The shape of the curve beyond the end point is determined primarily by the properties of the oxidant. For Ce(TV) in various media the value of El is different, and the potential varies correspondingly. The reasons for these effects are qualitatively the same as for the Fe(III)-Fe(II) couple. Note that three of the experimental curves with Ce(IV) in Figure 15-1 closely resemble the expected shapes the distortion of the curve for hydrochloric acid after the end point is due to the gradual oxidation of chloride by the excess Ce(IV). For further details see the discussion of Ce(TV) as a reagent (Chapter 18). 

Apart from acid-base titrations various addition-, substitution- and redox-reactions have been found to be of analytical interest. Iodine numbers of fats and essential oils may be determined i and bromine may be used to titrate organic compounds which can form bromoderivatives i. For the titration of phenol with bromine the addition of sodium acetate has been recommended. Redox reagents are in acetic acid chromium(VI) oxide, sodium permanganate, bromine, titanium(III) chloride and chromium(II) saltsi32,i33 xhe titrations are usually carried out in perchloric acid solutions and in an inert atmosphere but traces of water are tolerable. 

Evaluation reagents Col-1 ethanolic or methanolic sulfuric acid-l-UV254, Col-2 alkaline tetrazolium blue. Col 3 antimony/III/chloride, Col-4 perchloric acid, Col-5 p-toluene sulfonic acid, Col-6 chloramine T, Col-7 arzenomolybdate, Col-8 phosphomolibdic acid. 

---