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Mr. H. Wager. 



blue-green ring appears between the upper and lower liquids. Unfortunately 

 this test is not reliable, as dilute solutions of sugar and starch and various 

 other substances bring about the formation of a green or blue-green ring.. 

 This may be due to the fact that the sulphuric acid decomposes such 

 substances as starch and sugar, and that a transitory product of this, 

 decomposition may be formaldehyde. Consequently, although the reaction 

 is extremely useful for purposes of preliminary test, it cannot be relied upon 

 to prove the presence of formaldehyde. 



Rimini's test, as modified by Schryver, is extremely sensitive to form- 

 aldehyde and will easily detect 1/1,000,000. Here, however, the presence 

 of various substances in the crude chlorophyll seems to interfere with the 

 reaction, as shown by Schryver, and I have not been able to satisfy myself 

 that the colour reaction given by this test with solutions of bleached chloro- 

 phyll is due to formaldehyde. Colour reactions are obtained which seem to 

 indicate that formaldehyde is present in films exposed to light both in the- 

 presence and in the absence of carbon dioxide, but the reaction varies con- 

 siderably with certain limits. Sometimes a dirty orange colour is produced, 

 which is nothing like so distinct as the colour obtained with 1/1,000,000 of 

 formaldehyde, sometimes a deeper coloration which more nearly resembles 

 the formaldehyde coloration, but is more of an orange red or deep orange 

 than the bright, clear red of the formaldehyde reaction. In any case, none of 

 my experiments shows more than a very small quantity of formaldehyde in this 

 way, although the reaction given by Schiff s test in all cases indicated a much 

 larger amount of aldehyde. For example, a solution of bleached chlorophyll 

 showed a reaction for aldehyde with Schiffs solution equal to more than 

 1/25,000, but on testing the same solution with Rimini's test, the result 

 showed the presence of certainly not more than 1/1,000,000 of formaldehyde. 

 It appears to me from a large number of experiments that, although the 

 aldehyde in the bleached chlorophyll may contain a small quantity of 

 formaldehyde, the major part of it consists of some other aldehyde, the- 

 nature of which I have not been able to determine. 



The Oxidising Compound of Chlorophyll. 



The gaseous oxidising substance formed on exposure of chlorophyll to light 

 is soluble in water. The experiments of Usher and Priestley suggested the 

 possibility that it might be hydrogen peroxide. A solution was prepared 

 by exposing a film of chlorophyll on water to the light, which gave a strong 

 reaction with potassium iodide and starch, the iodine being liberated at 

 once and colouring the starch blue. Various well-known tests for hydrogen 



