TRANSACTIONS OF SECTION B. 685 
accumulation of the products of change unless we employ some means for removing 
them from the sphere of action as fast as they are formed. 
In the plant this removal is provided for by the living elements of the cell, by 
the chloroplast, assisted no doubt by the whole of the cytoplasm. We have here, 
in fact, the analogue of the ehemical sensitisers of a photographic plate, which act as 
halogen absorbers and so permit a sensible accumulation of effect on the silver salts, 
When we have succeeded in finding some simple chemical means of fixing the 
initial products of the reduction of carbon dioxide, then, and then only, may we 
hopefully look forward to reproducing in the laboratory the first stages of the great 
synthetic process of Nature on which the continuance of all life depends. 
The following Paper and Reports were read :— 
1. The Solidification of Hydrogen. By Professor J. Dewar, F.2.S. 
2. Report on a New Series of Wave-length Tables of the Spectra of the 
Elements. See Reports, p. 257. 
3. Interim Report on the Continuation of the Bibliography of Spectroscopy. 
See Reports, p. 256. 
FRIDAY, SEPTEMBER 15, 
The following Reports and Papers were read :— 
1. Report on the Relation between the Absorption Spectra and Chemical 
Constitution of Organic Bodies. See Reports, p. 316, 
2. Report on Isomeric Naphthalene Derivatives. See Reports, p. 362. 
3. A Discussion on the Laws of Substitution, especially in Benzenoid 
Compounds. Opened by Professor H. E. Anmstrone, £.2.8. 
1. In considering the formation of substitution derivatives from benzene and 
allied compounds, it is necessary to account for the very distinct behaviour of 
substances containing compound acid radicles (ze. radicles which in combination 
with OH form acids), which yield a large proportion of meta- derivative, whilst 
compounds containing other radicles yield ortho- and para-, and little if any 
meta- derivative. But no absolute distinction can be drawn, as much depends on 
the conditions under which the change takes place, a considerable proportion of 
meta- derivative being obtained, for example, from aniline by nitrating it in pre- 
sence of a large excess of sulphuric acid. 
2. In the case of an amino- compound, it is possible to trace the action through 
a series of stages. Thus in sulphonating aniline, the sulphate first undergoes 
conversion into sulphamic acid, and this is converted into either ortho- or para- 
sulphonic acid, according to the conditions under which it is placed. 
3. The process involved in the passage of sulphamic into sulphonic acid may 
be regarded as one of wsomeric change—t.e. it may be supposed that the SO,H 
group wanders from one part of the molecule to another, without leaving the 
system and temporarily entering into some other form of combination. 
In favour of this view is the fact that sulphonic acids are produced by 
the action of a sulphite on nitro- compounds under conditions which render the 
