Effect of Sodium Sulfite Purity on Color of Bodian Silver Staining of Insect Central Nervous Systems

Abstract

A low-contrast mauve color, different from the clear reds, purples and blue previously given by the Bodian Protargol (silver-protein) method with insect central nerve ganglia, was found to be caused by an impurity in the analytical grade sodium sulfite used in the hydroquinone silver developer. Impurities having the same effect were present in about half the samples of sulfite tested and appeared to be more complex sodium sulfoxy compounds. Recrystallization of the sulfites from hot water readily removed the impurity from every sample and restored the ability of the stain to give the desired colors.