McLeod—The Walden Inversion—A Critical Review ; . 517 
In accordance with the usual interpretation that nothing 
but lactic acid is obtained here as ultimate product, we have 
here in each of these three cases an inversion of optical activ¬ 
ity. These experiments serve to disprove Walden’s idea that 
the inversion takes place only with silver hydroxide, water, and 
analagous weak bases and never with bases or salts derived 
from such metals as sodium, potassium, etc., whose action on wa¬ 
ter gives rise to the strong bases. As a result, we see that the 
inversion may occur in any solvent, aqueous or non-aqueous, and 
is caused by comparable very slight concentrations of all bases, 
and of those salts which give bases by dissociation or hydrolysis. 
That an inversion of optical activity really takes place in any 
case, in the action of weak bases on halogen substituted fatty 
jicids, becomes decidedly open to question when we consider the 
folowing data obtained from experiments with dl (inactive) 
brompropionic acid. 
Space will not permit me to give, as I should like, a detailed 
description of all the experiments which I have carried out in 
order to determine the changes taking place in the action of sil¬ 
ver oxide and silver salts on d and dl brompropionic acid. I 
shall content myself with the following summary of results with 
dl mat.: 
In the action of silver acetate on d, 1 or dl brompropionic acid 
in absolute ether we should expect to get by double decomposi¬ 
tion, complete transformation to a acetyl hydroxy-propionic 
acid (acylated lactic) soluble in water of b. pt. 134° (15 mm.). 
CH 3 
HCBr-f AgOOCCHj 
COOH 
1 brompropionic 
CH 3 O 
I II 
HC-O-C-CH 3 + Ag Br 
COOH 
1 acetyl hydroxy propionic acid. 
We get, however, as main product a stiff gum insoluble in 
water. This gum by hydrolysis with water should give lactic 
acid of it consisted of oily lactid or poly lactyl lactic acid. By 
hydrolysis and distillation of the water at reduced pressure, I 
obtained, to my surprise, in place of mobile, syrupy lactic 
acid titrating over 90% in the cold, a gum, soluble in water, 
which had but very little mobility and which, with H/10 po¬ 
tassium hydroxide, titrated only 50% as a free acid. This 
