Sir: The determination of the oxirane ring in organic compounds has generallyinvolved reaction with excess hydrochloric acid in a variety of solvents.

CHEMISTRYgenerally applicable. It may also compensate for other possible interfering elements which were not studied in this paper. In addition, by reading the perchlorate blank separately one can obtain an indication of the presence of some unexpected element. COMPARISON WITHSTANDARD COLORIMETRIC METHODSThe sulfate procedures described lack the sensitivity of the thiocyanate method, so that the latter has an advantage in the determination of extremely small quantities of iron. The thiocyanate color lacks stability (8), however, which should make the sulfate method more suitable for accurate work in anything but the lowest concentration range. The interference of copper in the thiocyanate procedure (8) appears to lie greater than in the sulfate method.The o-phenatithroline procedure is subject to many difficulties (8) from which the sulfate method is free. The former cannot be used in extremely acid solutions, nor in the presence of appreciable amounts of perchlorates. The interference of many common metals is greater than in the sulfate method. An additional advantage of the sulfate method over others is that it requires no special reagents, so that the solutions can be recovered and tested for other elements if desired. OTHER METHODSThe procedures utilized above by no means exhaust the analytical possibilities present in ferric perchlorate and ferric sulfate solutions, if one is willing to isolate the iron. To illustrate this, NBS sample 161 (0.34% C, 1.29% Mn, 0.012% P, 0.005% S, 1.56% Si, 0.04% Cu. 64.3% Ni, 16.9% Cr, 0.03% V, 0.005% Mo, 0.47% Co, 15.0% Fe) was analyzed using sulfuric acid alone, the final concentration being 8 ml. per 100 ml. From a solution in which chromium was oxidized, iron was isolated by a double precipitation with ammonium hydroxide. The precipitate was redissolved, taken to sulfuric acid fumes, and the solution treated with a little hydrogen peroxide. Duplicate runs gave 15.0 and 15.1% iron.It is possible that the ferric sulfate complex can be used to determine larger amounts of iron accurately by differential or precision spectrophotometry. In this work, however, the temperature sensitivity would be a very important consideration.

No abstract

No abstract

No abstract