The Histochemical Detection of Beryllium

DURING an investigation of the toxic action of beryllium salts on experimental animals a histochemical test was developed to provide information on the distribution and site of action of beryllium. The technique is reported as an example of the application of chemical methods to histological problems. The reactions of beryllium salts with dyes of the triarylmethane series have been studied by Aldridge and Liddell (unpublished) in the course of developing a more satisfactory method for the chemical determination of beryllium in biological material. From this work it appeared probable that the coloured lakes formed by beryllium and dyes of the naphthochrome series would be suitable for the detection of the element in histological sections. A small number of naphthochrome dyes were tested for laking properties with concentrations of beryllium varying from i to 10 fig. per ml. in phosphate buffers ranging from pH 4-5 to 9-0. The dyestuff naphthochrome green B at pH 5 forms with beryllium an apple-green lake that contrasts with the blue-black colour of the dyestuff. Iron and aluminium share with beryllium the property of forming lakes with naphthochrome green B, but these lakes differ in colour. The ferric lake is dark blue-green and the aluminium lake is yellowish-green in colour. Further, the optimum pH for lake formation differs for the three elements. The colour reaction between beryllium and naphthochrome green B is maximal at pH 5 but iron and aluminium at this pH produce very slight colour changes, and these only at relatively high concentrations. In this way by selecting the dyestuff and pH range, it is possible to find conditions which permit a characteristic colour change with beryllium, but inhibit any reaction with other elements such as iron and aluminium. Napththochrome green B (C.A.C.) has Schultz Number 851 and is the sodium salt of pheno-oxy-dinaphtho-fuchsondicarboxylic acid. Its structural formula is