Potassium Dichromate

Chemical Description

Leather Tanning

• Potassium dichromate is used mainly as a precursor to potassium chrome alum in leather tanning.

Cleaning

• It has been used to make "chromic acid" for cleaning glassware and etching materials, but due to safety concerns with hexavalent chromium, this use is declining.

Construction

• It's an ingredient in cement that delays setting, improves density and texture, but can cause contact dermatitis.

Photography and Printing

• Used for hardening organic colloids like gelatin, making them insoluble and forming a relief image after washing away unhardened areas.
• Employed as photoresists in making metal printing plates.

Film Processing

• Potassium dichromate, mixed with hydrochloric acid, is used for chromium intensification to strengthen weak negatives in black and white photography.
• Can produce a positive transparency from a negative film when mixed with sulfuric acid.

Screen-Printing

• Used in photographic screen-printing, where it hardens a colloid on silk screens in light, creating a mask for printing.