228 Dr. S. B. Schryver. The Photochemical [Nov. 13, 



cyanide solution and acid be then added, the full colour due to the combined 

 formaldehyde will develop ; the hexamethylenetetramine in the presence of 

 water undergoes slight hydrolysis into ammonia and formaldehyde, and as 

 the latter, can be removed from the sphere of action in the presence of 

 phenylhydrazine, the reaction in the presence of this reagent can proceed 

 to completion, and the total combined formaldehyde can be thereby 

 estimated. This reaction will be discussed in greater detail below, when 

 considering the mechanism of the formaldehyde formation of chlorophyll. 



In the presence of other pigments, the method of carrying out the reaction 

 can be conveniently modified, especially when the quantities of formaldehyde 

 present are only small. The reaction mixture, after addition of the reagents 

 (phenylhydrazine and ferricyanide reagents and hydrochloric acid), is diluted 

 with water in a small separating funnel, and ether is added. After shaking 

 up, the hydrochloride of the chromatogenic base is dissociated, and the free 

 base passes into the ethereal solution ; the latter is separated off from the 

 underlying aqueous layer. On addition of concentrated hydrochloric acid 

 to the ethereal solution, the base readily passes into the acid, in the form 

 of the coloured hydrochloride. By using only a small quantity of acid, the 

 sensitiveness of the test is largely increased, as the colour can be finally 

 contained in only 1 or 2 c.c. of solution, instead of 18 c.c. as required in the 

 original test. The test in this form has been applied in investigating the 

 synthesis of formaldehyde by chlorophyll. 



The test appears to be characteristic for formaldehyde. Commercial 

 solutions of acetaldehyde yield a very faint pink colour, when in relatively 

 strong solutions (1 to 2 in 1000), but this is due to contaminations with 

 small quantity of formaldehyde, derived from methyl alcohol. Furfur- 

 aldehyde, which can certainly be obtained from plants, gives a characteristic 

 reaction when present in sufficient concentration. On addition of phenyl- 

 hydrazine and ferricyanide reagents to furfuraldehyde solution (1 in 1000) 

 an apricot yellow colour is formed, which turns a dirty-green colour on 

 addition of concentrated hydrochloric acid ; this, however, is only transient, 

 and rapidly disappears. If, shortly after addition of tlie acid, and before the 

 disappearance of tlie green colour, the reaction mixture be diluted and 

 extracted with ether, and the ethereal solution be then extracted by acid, 

 the latter takes np a green pigment. This reaction, liowover, is only 

 obtained, if the dilution and extraction with ether be made very shortly 

 after addition of the acid, and in this respect (as also in colour) it differs 

 from the forinaldehydc pignunit, which is fairly stable. Furfuraldehyde, 

 furthermore, gives no reaction with the reagents employed in the form- 

 aldehyde test when the diluticm reaches 1 in 100,000. The reaction, to be 



