4. For what two purposes are melting points routinely used? a. b. 5. Three test tubes contain white crystalline organic solids A, B and C, each of which melts at 149-150°C. A 50-50 mixture of A and B melts at 130-139°C. A 50-50 mixture of A and C melts at 149-150°C. In what range would a 50-50 mixture of B and C probably melt? What can you say about the identities of A, B and C?