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Mr. H. Wager. 



same way with the formation of an oxidising substance capable of bringing 

 about the liberation of iodine from potassium iodide. Thus, if strips of 

 paper are soaked in solutions of the following dyes — methyl violet, methyl 

 green, eosin, fuchsin, and fluorescein, and are then exposed to light and 

 afterwards treated with a 10-per-cent. solution of potassium iodide, the 

 iodine is liberated and the starch contained in the paper is coloured blue or 

 reddish blue, a strong reaction being obtained in all cases. Cyanin, on the 

 other hand, although readily bleached by the light, does not give this 

 reaction. 



Experiments made with narrow glass tubes lined with a thin layer of 

 methyl violet and eosin show, on exposure to light, that, during the process 

 of bleaching, oxygen is used up, but this is not the case with cyanin, which 

 becomes completely bleached without any appreciable rise of water in the 

 tube. In the case of methyl green and eosin, the absorption of oxygen 

 does not take place as rapidly and is not so pronounced as in the case of 

 chlorophyll. 



The Photo-decomposition of Chlorophyll in a Brown Sea>weed — Laminaria. 



In order to make experiments on the chlorophyll contained in the brown 

 sea-weeds, I collected pieces of fresh fronds of laminaria on the sea-shore and 

 brought them home wrapped in pieces of ordinary white paper. On removing 

 the paper, I found a blue coloration here and there where the paper had been 

 in close contact with the fronds. It was obviously the blue starch coloration 

 due to iodine. I at first thought that it might be due to chlorine,* possibly 

 contained in the paper, acting upon an iodine compound in the sea-weed and 

 causing the liberation of iodine. A statement in Pfeffer's ' Physiology,' however, 

 led me to suspect that the coloration might be due to free iodine given off 

 by the laminaria itself. To test this, I took some .fresh pieces of a frond of 

 laminaria and placed them in a dilute starch solution free from chlorine. The 

 solution became coloured blue, showing quite clearly the presence of free iodine. 

 The colour disappeared again* in a very short time, much more rapidly, so it 

 appeared to me, than it would have done in a starch solution coloured by an 

 ordinary solution of iodine. I accordingly tried the experiment again, and 

 found on comparing ib with a starch solution coloured with iodine to the 

 same depth of colour, that the laminaria solution lost its colour several hours 

 before the other. This indicated that the iodine was taken up again by 

 the laminaria from the starch solution, and it occurred to me that this might 

 be due to the slime which is secreted by the laminaria and which was found 



* Chlorine is used in the bleaching of paper. 



