Summary.— An investigation of photocontact dermatitis occurring in a dye manufacturing process is described. Sixteen employees were studied by photopatch testing to the complete anthraquinone‐based dye: Disperse Blue 35 and to chromatographically separated bands. By irradiation of the skin with visible light between 400 and 700 nm evidence was obtained to show that the complete dye produced photo‐contact dermatitis in individuals, whether they had previously been exposed to it or not. Using the same technique, only 4 of the 10 constituent hands produced a similar photocontact reaction.

The rate of reduction of acetatopenta-amminecobalt(iii) by iron(\\) is greatly enhanced by the presence of Nmethylirninodiacetic acid (H,L). In glycine buffer medium the effective reducing agent is FeIIL, and the reaction is of the second order: -d[CoIII]/dt = ~,[CO~~~(NH,),OAC~+][F~~~L] with k, = (1.52 f 0.12) x 10-3 dm3 rnol-l s-l at 25 "C, ionic strength 1 -OM (NaCIO,) ; AH2$ = (21 -7 f 1.1) kcal mol-l.As part of a of the energetics of electrontransfer reactions in solution we have determined kinetic parameters for the reduction (1) of acetatopenta-amminecobalt(II1) by iron(I1) in the presence of N-methyliminodiacetic acid. In equation (1) and throughout thepaper L2-= MeN(CH2C02),2-. EXPERIMENTALMaterials.-Aquopenta-amminecobalt(Ir1) perchlorate was prepared from carbonatopenta-amminecobalt (111) nitrate 6 and repeatedly recrystallised from dilute perchloric acid.Acetaiopenta-amminecobaZt(I1I) pevchlorate. Following Linhard and Weigel,6 the aquopenta-ammine perchlorate (8.0 g) and AnalaR anhydrous sodium acetate (4.0 g) were dissolved in water (30 cm3), treated with AnalaR glacial acetic acid (0.4 cm3), and evaporated to dryness a t 60 "C. The solid was redissolved in hot water (90 cm3), treated with saturated NaC10, solution (10 cm3), filtered hot, and allowed to crystallise. The product was recrystallised twice from water containing a few drops of acetic acid; yield 2.2 g. Cobalt content was determined by the method of Gould and Taube [Found: Co, 14.3 f 0.3, 14-9 f 0.3 (two determinations). Calc. for Co(NH3),0Ac(C10,),: Co, 14.68%]. Visible spectrum: Lx. 503 nm, E: = 77.8 dm3 mol-l cni-l; 352 nm, E = 65-0 dm3 mol-l cm-1. Linhard and Weigel6 found the same Amax. but lower extinction coefficients, 66.0 and 50.1 dm3 mol-1 cm-1 respectively. Other samples of the complex were prepared following Linhard and Ram8 With different samples, rates of the reaction under investigation agreed within Glycine. The commercial product (B.D.H. reagent grade) was recrystallised from water.N-Methyliminodiucetic acid. The commercial product (Aldrich) was recrystallised from water and had m.p.

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