Direct Black 38 (Chlorazol Black E) is a black azo dye that absorbs various colors of light and is commonly used in the textile industry.Direct Black 38 is genotoxic and induces unplanned DNA synthesis in rat liver and bone marrow micronuclei.

Instructions
I. Solution preparation
1. Recommended concentration: 1–5% (mass/volume). Dissolve in deionized water and dilute as needed.
Storage conditions: The stock solution is stable under refrigerated conditions at 4°C. Avoid prolonged exposure to strong light or high temperatures to prevent degradation.
II. Operation steps
1. Textile dyeing
1). Prepare the dye bath: Heat the dye solution in the range of 60–90°C and maintain uniform mixing. Adjust the dye concentration according to the material and the expected color depth.
2) Immerse the material in the dye bath, usually for 30–60 minutes.
3) Fix and wash: Use an appropriate amount of salt or alkaline substances (such as sodium carbonate) as an auxiliary agent to enhance binding.
4) Wash after dyeing to remove excess dye.
2. Biological experiments
1) Cell or tissue staining: Dilute the stock solution (working concentration is 0.1–1%).
2) Directly apply or immerse in the sample, the staining time can be optimized to 5–30 minutes.
3) After staining, rinse with appropriate buffer (such as PBS) to remove unbound dye.
4) Microscope observation: Usually observed under bright field microscope, choose appropriate light source and filter to improve contrast.