Complementary study on the use of the potassium Reinecke's salt as a chemical actinometer

Abstract

Aqueous solutions of K[Cr(NH3)2(SCN)4].H20 (the potassium Reinecke's salt) can be used as a photochemical reference system for radiations in the visible region. The results of complementary studies o n the improvement of analytical procedures, the direct synthesis of the salt and its thermal reactivity are reported. The possibilities of the application of the system are also discussed.

A revised experimental protocol for implementing the actinometry method with the Reinecke’s salt

“…In this short note, the classical experimental protocol to determine the incident photon flux density by actinometry with the Reinecke'salt was revised. As the use of the acid perchloric could cause serious damages to the environment and injuries to experimenters, the proposed method consisted in substituting the perchloric acid by a less hazardous a thermal pathway [17]. The applied dilution factor θ and the final pH were then equal to 24 and 1.2 for all the samples, respectively.…”

“…It is important to note that the absorption of the by-product, [Cr(NH 3 ) 2 (NCS) 3 (H 2 O)], is of the same order of magnitude than the one of the actinometer, thus implying that its absorption should be taken account in the modelling [16]. Furthermore, as described by Szychlinski et al [17], under acidic condition, the by-product could react with water according to Eq. 2 were negligible at 450 nm.…”

4,4′-Dimethylazobenzene as a chemical actinometer

“…eters commonly used nowadays are not commercial and require synthetic efforts or purification procedures: Aberchrome is no longer commercially available and must be synthesized; potassium ferrioxalate and Reinecke's salt must be recrystallized to obtain a suitable purity [25,27]; azobenzene is commercially available, but known to be carcinogenic and its use should be discouraged. • Experimental procedure: E-DMAB isomer does not undergo thermal reactions or degradations, thus a blank is not required (as for Reinecke's salt [26] and ferrioxalate [7]).…”

“…• Experimental procedure: E-DMAB isomer does not undergo thermal reactions or degradations, thus a blank is not required (as for Reinecke's salt [26] and ferrioxalate [7]). The absorbance recording does not need any dilution (as for Reinecke's salt) [25,27] or addition of reactants (as o-phenanthroline for ferrioxalate or Fe(NO 3 ) 3 for Reinecke's salt). Therefore, the manual errors arising from the procedure are largely minimized using DMAB.…”

“…Among the numerous actinometers reported so far, the most employed ones are the potassium ferrioxalate-or Hatchard-Parker actinometer (250-500 nm) [6][7][8][9][10][11][12][13], the Aberchrome 540 (310-375 nm and 435-535 nm) [14][15][16][17][18][19][20][21][22][23][24], and the potassium reineckate-or Reinecke's salt (316-750 nm) [4,[25][26][27][28]. However, despite their well consolidated and good performances, none of these fulfills all the abovementioned requirements.…”