Alizarin Red S, buffered pH 4.0, is an aqueous solution of Alizarin Red S (C.I.: 58005) and contains sodium acetate and acetic acid. This solution finds application in various fields, such as histology, textile industry and food industry.

In histology, Alizarin Red S, buffered pH 4.0, is used especially for calcium detection in tissue sections. Due to the specific binding of Alizarin Red S to calcium ions in mineralized tissues, such as bones or teeth, these areas can be selectively stained and visualized under the microscope. The use of Alizarin Red S at a buffered pH of 4.0 has the advantage that the solution remains stable in an acidic environment, increasing the selectivity and sensitivity of calcium binding.

The chemical functionality of Alizarin Red S is based on its ability to act as a pH indicator and to be used as a complexing agent for metal ions, especially calcium ions. The buffer components sodium acetate and acetic acid stabilize the pH at 4.0, which improves the specificity for calcium ions in histological applications.

The special suitability of Alizarin Red S, buffered pH 4.0, lies in its high sensitivity and accuracy in pH determination and in its ability to accurately and reliably visualize calcium deposits in tissue sections.