8 



EXPERIMENT 



68. DIRECT DYEING 74 



69. INDIRECT DYEING. MORDANTING 75 



70. TO DETECT THE PRESENCE OF FAT AND OlL IN FOODS . 76 



71. To DETECT ARTIFICIAL COLORING MATTER IN FOODS . 76 



72. To DETECT ARTIFICIAL COLORING MATTER IN FOODS . 77 



73. To DETECT ALUM IN MAKING POWDER . . ..- . 78 



74. To DETECT FORMALDEHYDE IN MILK .... 78 



75. To DETECT GELATIN IN MILK AND ICE CREAM . . 78 



76. TO DETECT BORIC ACID AND SULPHIDES IN MEAT . . 79 



77. To DETECT COTTONSEED OIL ... . . .79 



78. CHEMICALS AS PRESERVATIVES . . . . . .80 



79. THE EFFECT OF HEAT ON BACTERIA . . . .81 



SOUND 



80. SOUND DUE TO VIBRATION . ... . . .82 



81. THE REFLECTION OF SOUND .V. . 83 



82. RESONANCE < .. . 84 



83. A TEST FOR HEARING . * . . . . . 84 



ELECTRICITY 



84. SOME EFFECTS OF ELECTRICITY .... . . . . . 86 



85. ELECTRICITY AS A SOURCE OF HEAT . .- .. . . 88 



86. ELECTRICITY AS A MAGNET . . . . . . 89 



87. THE ELECTRIC BELL 90 



88. MAGNETS AND THEIR ACTION ON IRON FILINGS . . 91 



89. THE ACTION OF MAGNETS ON EACH OTHER . * . 92 



90. OTHER RESPECTS IN WHICH AN ELECTRIC CURRENT is LIKE 



A MAGNET . . . . 93 



91. THE PRINCIPLE OF THE MOTOR 94 



92. THE PRINCIPLE OF THE DYNAMO AND THE TELEPHONE . 95 



