Transcriber's Notes: Illustration has been moved so it does not break up the paragraph. As this was a hand-written thesis, the spelling, punctuation and hyphenation is very inconsistent. The original spelling, hyphenation and punctuation have been left unchanged. Subscripts appears as _{X} where X is an integer. Multi-line curly brackets have been replaced with multi-line square brackets. ON SULPHONFLUORESCEÏN AND SOME OF ITS DERIVATIVES. DISSERTATION Presented for the Degree of Doctor of Philosophy at the Johns Hopkins University by C. Willard Hayes, 1887. Contents. p. Introduction 3. I Ortho-sulpho-benzoic acid. Preparation from toluene and H_{2}SO_{4} 7. ” ” para-nitro-toluene and H_{2}SO_{4} 8. Oxidation of toluene-o-sodium sulphonate 12. Preparation of Sulphinide from ” ” 14. ” ” ” by chlorsulphonic acid. 17. Conversion of sulphinide into o-sulphobenzoic acid. 25. Analysis of and crystallography of ” ” ” 28. II Sulphonfluoresceïn--previous attempts 29. Preparation and purification of s-fluoresceïn 30. Analyses of ” 34. Properties of ” 35. Salts. Ba. and Ca. of ” 37. Acetyl derivative of ” 41. Br substitution products of ” 42. Action of H_{2}SO_{4} on ” 44. Action of HCl on ” 45. Reduction of ” 46. Conclusion. 47. On Sulphonfluoresceïn and some of its Derivatives. Introduction. The close analogy in composition and structure between phthalic acid and ortho-sulpho-benzoic acid suggests the possibility of obtaining from the latter, by its action on phenols, substances analogous to the phthaleïns. If such compounds could be made they would afford a favorable opportunity of studying the effects produced in the properties of a compound by the replacement of CO by SO_{2}. It was with a view to such study that the following discussed work was undertaken at the suggestion of Prof. Remsen and carried on under his constant guidance.