JANUABY 27, 1911] 



SCIENCE 



13f 



with a 1.5 per cent, solution of uranium 

 acetate. When the experiment was carried 

 out in the sunlight there was obtained a 

 precipitate of the hydroxides of uranium 

 together with a small amount of peroxide. 

 The results are explained on the sup- 

 position that the carbonic acid is resolved 

 into formaldehyde and a percarbonic acid, 

 H2CO4, in accordance with the following 

 equation: SH^COs = CH^O + 2H2CO,. 

 The percarbonic acid as fast as formed 

 breaks down into hydrogen peroxide and 

 carbon dioxide. To support this interpre- 

 tation of the course of the reaction, Bach 

 refers to the work of Wurster,^' who 

 claimed to have demonstrated the presence 

 of hydrogen peroxide in plants, although 

 Wurster's results had been strongly chal- 

 lenged by Bokorny." In 1898 Bach^° 

 again returned to the problem, this time 

 using palladium as a catalyzer. Carbon 

 dioxide was passed through water contain- 

 ing palladium held in suspension. In the 

 clear liquid obtained by filtering off the 

 palladium Bach claims to have established 

 the presence of formaldehyde. 



While the experiments of Bach are in- 

 geniously conceived and are of great in- 

 terest, his interpretation of the results do 

 not appeal to one as at all conclusive. The 

 most that can be said is that the generation 

 of formaldehyde and hydrogen peroxide 

 under the conditions of the experiments is 

 probable. Their presence must be regarded 

 as inferred rather than proved. It is not 

 strange therefore that his results have 

 been criticized. In 1904 Euler-" repeated 

 the work and concluded that the carbon 

 dioxide in Bach's experiments did not 

 enter into the reaction at all since exactly 

 the same results are obtained if one sub- 



" Ber. d. chem. Gesell., 19, p. 3195. 



^"Ber. d. chem. Gesell., 21, p. 1100. 



^° Compt. rend., 126, p. 479. 



™Ber. d. chem. Gesell., 37, p. 3411. 



stitutes a current of hydrogen or nitrogen 

 for the carbon dioxide. 



On the other hand, Usher and Priestley-^ 

 in 1906 reported that "the experiments of 

 Bach have been repeated and confirmed, 

 both as to the production of peroxide and 

 formaldehyde." Oddly enough, however, 

 they gave no account as to their manner 

 of confirming these results, and since Bach 

 himself rather inferred than proved the 

 presence of these two compounds the state- 

 ment of Usher and Priestley is not wholly 

 satisfactory. In order to meet the criti- 

 cism that the production of formaldehyde 

 in Bach's experiments may have resulted 

 from the reduction of the acetic acid 

 which would undoubtedly be formed by 

 the hydrolysis of the uranium acetate 

 used. Usher and Priestley"- in a later ar- 

 ticle described a series of experiments in 

 which uranium sulphate was substituted, 

 for the uranium acetate. In these experi-^ 

 ments no formaldehyde could be detected., 

 although the authors report that "a study- 

 of the reactions involved favors the view- 

 that it is formed as a transitory intermedi- 

 ate product." In their original work 

 Usher and Priestley were led to conclude 

 from experiments on plants {Elodea were 

 used) that the generation of formaldehyde 

 in the plant from carbon dioxide and 

 water is not a vital process at all since 

 small plants of Elodea in which all life 

 had been destroyed by immersion in boil- 

 ing water accumulated perceptible amounts 

 of formaldehyde when exposed to sun- 

 light in a moist atmosphere of carbon di- 

 oxide. The tests for formaldehyde were 

 made directly xipon the leaves as well as 

 upon the distillate from the leaves. The 

 principal tests employed were (a) the de- 

 velopment of color in Schiff's reagent, (&) 

 the formation of methyleneaniline with 



'^Proc. Royal Soc, B, 77, p. 370. 

 '^'Proo. Royal Soc, B, 78, p. 318. 



