Experiments with preservatives 22 Sodium benzoate 22 Salt 23 Sugar 23 Spices 24 Water infusions 24 Acetic acid extracts 25 Oil extracts 25 Vinegar and acetic acid 26 Oil 27 Study of Penicillium in ketchup 28 Development 29 Reproduction 29 Growth in ketchup 30 Temperature tests 31 Histological structure of ketchup 33 Microscopical examination of some commercial brands 34 Summary 35 ILLUSTRATIONS. PLATES. Page. PLATE I. Penicillium. Fig. 1.--Conidia, normal growth and in various stages of germination, some with branching hyphæ. Fig. 2.--Conidiophore, showing unusually large development of conidia; from culture in moist chamber 28 II. Cultures from ketchup preserved with sodium benzoate. Fig. 1.--Conidia and hyphæ from culture in experimental ketchup containing one-sixteenth of 1 per cent of sodium benzoate. Fig. 2.--Conidia and hyphæ from culture in experimental ketchup containing one-tenth of 1 per cent of sodium benzoate 28 TEXT FIGURES. Fig. 1. A model receiving platform 8 2. Large receiving room showing the sorting belt 9 3. A section of a kitchen showing the copper cookers 10 4. An example of factory practice 12 5. Another factory interior 14 EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP. INTRODUCTION.