High-quality dark blue cobalt glass filter is used in sodium and potassium salt flame tests. When a flame is viewed through this filter, the color orange is blocked so that a violet-colored flame is visible. Sold as packs of 6. Additional Info: High-quality dark blue cobalt glass filter is used in sodium and potassium salt flame tests. When a flame is viewed through this filter, the color orange is blocked so that a violet-colored flame is visible. Sold as packs of 6. Package Size(L x W x H): 4.5 X 4.5 X 1 (IN) Categories: Glass Plates, Cobalt HTS Code: 7017.90.5000 UNSPSC: 4.11218e+007 Country Of Origin: INDIA