314 REPORTS ON THE STATE OF SCIENCE, ETC. 



forms ill solution an addition complex with carbonic acid. On exposure of this 

 solution to visible light formaldehyde is produced, the same result being 

 obtained with other coloured basic substances as photocatalysts (Baly, Heilbron, 

 and Barker, Trans. Chem. Soc, 119, 1025 (1921)). 



These two examples are suflicient to demonstrate the reality of photocatalysis 

 which was foretold from the phase theory. The formation of formaldehyde 

 from carbonic acid possesses an added interest because this reaction undoubtedly 

 constitutes the first step in the growth of living plants. As is well known, 

 sunlight contains no ultra-violet light of such short wave-length as 200/1/1, and 

 consequently the CO2 assimilated by the plant cannot be converted by sunlight 

 into formaldehyde without some assistance. Willstatter has shown that the 

 CO2 absorbed by the living leaf combines in the form of H2CO3 with the chloro- 

 phyll. The chlorophyll therefore acts as the photocatalyst, and on absorbing 

 visible light from the sun it radiates this energy again at its molecular frequency. 

 Owing to the identity of the molecular frequencies of the two components of 

 the complex this energy is reabsorbed by the carbonic-acid component, which 

 thereby becomes activated and reacts to form formaldehyde and oxygen. 



This photosynthetic production of formaldehyde has very important conse- 

 quences, since the molecules when freshly synthesised possess a very remarkable 

 reactivity. Formaldehyde exhibits an absorption band at the wave-length of 

 290 /i/i or the frequency of 1.0345x101°', and when it is exposed to light of this 

 frequency each molecule absorbs one phase quantum, and is thereby converted 

 into a phase of very high energy content. This phase is the same as that in 

 which the newly photo; ynthesised molecule exists, for the two give identical 

 reactions. One of these reactions is the combination with the potassium nitrite, 

 which is always present in the leaf, to give formhydroxamic acid. This substance 

 at once reacts with more activated fcrmaldehyde to give a-amino acids, pyridine, 

 piperidine, pyrrole, pyrrolidine, glyoxaline, quinoline, /.<o-quinoline. indole, and 

 derivatives of xanthine. These reactions have been observed in the laboratory 

 with both photosynthesised formaldehyde and photochemically activated form- 

 aldehyde. A second reaction of the activated formaldehyde is its polymeri- 

 sation to form hexoses, and this reaction has also been realised in the laboratory 

 with lioth photosynthesised and photochemically activated formaldehyde. 



According to the phase theory these various substances, a-amino acids, 

 nitrogen bases, and hexoses, are produced in highly reactive phases, and will, 

 therefore, possess reactivities new and strange to those who only know the 

 compounds in their normal and less active phases. The formation of substituted 

 a-amino acids, like histidine, and the condensation of these to form proteins, is, 

 therefore, not by any means extraordinary, nor is the condensation of hexose 

 molecules to form cane-sugar and then highly complex starches and carbo- 

 hydrates to be wondered at, for all these reactions are merely those characteristic 

 of phases with greater energy content than the phases known to the organic 

 chemist, ilany of these reactions have actually been realised in the laboratory 

 by the use of activated formaldehyde, and the following substances have been 

 photosynthesised : Several substituted a-amino acids including histidine, three 

 alkaloids including coniine, and a mixture of carbohydrates as yet not identified, 

 but probably of greater complexitv than cane-sugar (Balv, Heilbron, and Hudson, 

 Tia7is. Chem. Soc, 121, 1078 (1922)). 



The phenomenon of photocatalysis and its applications afford the strongest 

 evidence yet found for the theory of molecular phases. Although it may be 

 argued that it has little to do with absorption spectra, such argument can only 

 be inspired by misunderstanding, for it is entirely based on the frequencies 

 which characterise substances. Every molecular phase is characterised by its 

 own energy content, its own absorption frequency, and its own chemical re- 

 activity. Evidence for the reality of these phases is derived from energy 

 relationships, from absorption spectra, and from chemical reactions. The fact 

 that the chemical arguments, though based on the absorption of energy at the 

 characteristic frequencies of molecules, are not in every case completed by a 

 knowledge of the absorbing frequencies of all the phases that take part in a 

 reaction, does not detract from those arguments. When a molecule is converted 

 by the supply of energy into a phase which reacts, that phase has onlv a 

 transient existence, and there is as yet no means of identifying it by' its 



