Letter from Howard Walter Florey to F Roffey, The Distillers Company Ltd, St James's Square, London Says that Galxo and Company claim to have produced a penicillin containing 10% K and 90% G - says that there is no essential difference between F, X and G in treatment of syphilis - says War Office has asked his advice about getting a new specification - thinks he shall draw it up in terms of exclusion of K - gives references to papers on factors which interfere with the activity of streptomycin. 19 February 1948