AbstractIn growing crystals by the new gel technique a principal difficulty may arise in that it may be difficult or at times impossible to choose two nutrients that may react to produce the desired crystals. With some crystals, the pair of nutrients that may appear practically most suitable, may not react at all or the rate of reaction may be exceedingly small. Further work on the new gel technique has now led to an improvement of the technique by which it is feasible to impart activity to nutrients which are normally non‐reactive or to enhance the reactivity of generally less reactive nutrients. Large needles of PbCl2and PbBr2have been grown in silica gel by this improvement of the new gel technique. The interesting phenomenon of transformation of needles of PbCl2and PbBr2into single crystals has been investigate and the various aspects of growth systematically studie