Ammonium hydroxide was treated with concentrated sulphuric acid for the preparation of ammonium alum. In this reaction the mole ratios of Al/SO4 were adjusted to 1:2 to 2.4.
Instead of using aluminium chlorohydrate or aluminium zirconium to block pores and prevent sweating the natural deodorants may contain a crystal form or aluminium, known as ammonium alum.
The sections were subsequently stained with various alcoholic dilutions of the dye in acidic, alkaline and neutral media, with the use of 1% acetic acid, potassium ammonium alum and ethanol, respectively.