McLeod—The Walden Inversion—A Critical Review. 515 
edly be found as a result of most careful experiments to estab¬ 
lish the changes which actually occur in the action of various 
reagents on optically active bodies, all of which have been as 
sumed to take place as a result of a simple metalepsis. Scarcely 
any of these changes have been rigidly established. Almost 
without exception, 30 satisfactory figures for solubility, water 
of hydration and percentage of zinc have sufficed to prove the 
presence of lactic acid in the form of its zinc salt. When the 
reader weighs carefully the evidence presented in the experi¬ 
mental part of this paper, he will undoubtedly agree with me 
that the Walden inversion simply represents another case of 
some peculiar co-incident results which have often led scientists 
astray. 
Seme recent experimental results. 
This investigation was undertaken at the suggestion of Prof. 
J. U. Uef of the University of Chicago with the purpose of ob¬ 
taining independent experimental evidence to support his idea 
that the four valences of the carbon atom are not mutually equi¬ 
valent, but only in pairs. Acording to this idea we ought to be 
able to prepare two space isomeric diazo propionic esters resp. 
d and 1. 
C 
N— + COOR 
d body 
N- +CH 3 
C 
N+ ^Tcoor 
1 body 
The preparation of diazo fatty esters is no easy matter and 
besides it was necessary first to become thoroughly familiar 
with the properties of the optically active acids of the C 3 
series. 
Optically active alanin was prepared according to Fisher’s 
method by resolution of benzoyl alanin by means of brucin in 
so Wislicenus: Ann. 166, 6; Heintz: Ann. 156, 25; Ann. 157, 295; 
Wiehelhaus: Ann. 143, 1; Friedel & Machuca, Comptes Rendus, 13, 408; 
Buff: Ann. 140, 156; El Fisber; Ber. 40, 1051. 
30 e. Fisher & A. Skita: Zeit. fur physiol. Ch. [1901] Vol. 33, 190; 
E. Fisher & Zemplen: Ber. Dec. 1909, 42, 4878-4892; Beckurts & Otto: 
Ber. 18, 222-238. 
