12 H. A. SPOEHR 



for these investigations on account of the large per cent of clear 

 days and the exceedingly high light intensity. A great number 

 of experiments have been made with the object of reducing 

 carbon dioxide by means of light from various sources. 



In view of the contradictory results given by Usher and 

 Priestley, Berthelot and Gaudechon and Stoklasa and his co- 

 workers, it was thought important to try out the effect of ultra- 

 violet light on carbonic acid and its salts. It was found that 

 neither carbon dioxide as a gas with water vapor, nor CO2 dis- 

 solved in water, in various experiments, exposed from one to one 

 hundred and fifty hours, ever yielded tests for formaldehyde 

 which were sufficiently distinct to definitely establish the pres- 

 ence of that substance. The tests employed for formaldehyde 

 were: 



1. Diphenylamine in concentrated sulphuric acid.^^ 



2. 0.5% resorcin with concentrated sulphuric acid.^^ 



3. 40% NaOH plus 5% resorcin. 



4. Rosaniline in sulphurous acid plus hydrochloric acid.^° 

 Instead of using a metallic alloy to produce nascent hydrogen, 



as Stoklasa had done, this was prepared electrolytically. A 

 large quartz flask, partially filled with a KHCOj solution, and 

 bearing a three-hole stopper was used. Through one hole passed 

 a glass tube to the bottom of the flask for the supply of CO2, 

 this tube also carried the negative wire from a small electric gen- 

 erator, the wire was fastened to a platinum electrode from which 

 the hydrogen was evolved at the bottom of the flask. The sec- 

 ond hole was used for the electrolytic bridge : a glass tube, filled 

 with K2CO1 solution, connecting with the solution in the flask 

 and the other end with a dish of K2CO8 solution; in this dish was 

 placed the positive pole of the generator. Through the third 

 hole in the stopper passed a tube to carry off the gases from the 

 flask to the cooled absorbing vessels. Thus, nascent hydrogen 



2« Grafe, V., Ost. bot. Zeitschr. 64: 289-91, 1906. 



^' Abderhalden, E., Handbuch d. Biochem. Arbeitsmethoden. II, 15. Lebbin, 

 Zum Nachweis d. Formaldehyds. Pharm. Ztg. 42 : 18, 1897. 



'" Fincke, H., Nachweis von Formaldehyd in den Pflanzen. Biochem. Zeit- 

 schr. 52:219, 1913. 



