62 ALDEHYDES 



A solution of chlorophyll is made with carbon tetrachlor- 

 ide, and in it filter paper is soaked. The filter papers are 

 dried, moistened with water, and placed on the inner surface 

 of a glass bell-jar. The bell-jar is inverted over a dish of 

 water, sealed from the air, and exposed to sunlight. The 

 chlorophyll papers are gradually bleached ; when pale green 

 in colour the water in the dish gives a positive reaction for 

 aldehyde. The same result was obtained when the carbon 

 dioxide was excluded or increased to 10 per cent, which indi- 

 cates that the aldehyde is due to the colouring matter rather 

 than the carbon dioxide. Like results obtained when various 

 aniline dyes, notably methyl green and iodine green, were 

 used in place of the chlorophyll. 



