466 SECTIONAL TRANSACTIONS.—B. 
simplest form with a divalent metal or with hydrogen in the manner : 
(C,H,N,),H2 or (CsH,N2),.metal. The mode of synthesis and the re- 
actions of these compounds indicate that they contain a system of iso-indole 
rings linked by nitrogen atoms and forming a large ring with the metal held 
in the centre by primary and secondary valencies. 
The phthalocyanines exhibit two features of special interest. First, their 
fundamental unit resembles that of porphin, which is the basis of the 
naturally occurring pigments of the chlorophyll and hemin group. The 
structural unit of the natural pigments differs in containing no benzene 
ring and in having methine (— CH =) links in place of nitrogen. 
C—N= CGH 
; 4\/\ CH/\ 
Phthalocyanine Pwd IN Porphin Unit | oN 
Unit \ fo P CEN in 
| | 
Secondly, the phthalocyanines are among the most stable of complex 
organic compounds. For example, the copper compound sublimes un- 
changed at 600°; dissolves in strong sulphuric acid without decomposition 
or loss of metal ; and resists the action of molten caustic potash. Other 
compounds of the group show a similar stability. 
Dr. N. V. Srpewick, F.R.S. 
The plane arrangement which these formule require us to ascribe to 
the covalencies of the metals they contain is of great interest. According 
to the theory, a plane distribution of four covalencies of an atom is possible 
(1) for four of the six covalencies of a 6-covalent atom, (2) for a 4-covalent 
atom of one of the later transitional elements, such as nickel and perhaps iron. 
The iron compounds described would then come under (2), and the 
magnesium complexes could only exist under (1) if the atom was 6-covalent, 
which would explain why these compounds have two molecules of water. 
An interesting test would be to examine the beryllium complexes of these 
substances. On the theory, beryllium cannot form more than four covalen- 
cies, and these cannot lie in a plane, but must be tetrahedral. It should, 
therefore, be incapable of forming links with four nitrogen atoms in a plane. 
On the other hand, beryllium co-ordinates with such energy that it will form 
the complexes if it can; and we could thus discover whether the steric 
conditions permit of their formation. 
Friday, September 8. 
Discuss1on on Hormones (10.0) :-— 
Prof. Dr. F. KocL.—Plant growth hormones (Auxin a and Auxin b). 
(Ordered by the General Committee to be printed im extenso. See p. 600.) 
Mr. G. A. D. HasLewoop.—Earlier chemical work on estrin. 
From 1903 onwards, many extracts of ovarian tissue were prepared which 
could produce cestrus in normal and ovariectomised animals. In 1923, 
vaginal cornification was adopted by Allen’and Doisy as a method of assay. 
