McLeod—The Walden Inversion—A Critical Review. 507 
the free acid. That the inversion took place with the free acid 
rather than with the ester, Fisher decided from the fact that 
esters were less inclined to optical reversals than the correspond¬ 
ing acids. Having established as above that the action of phos¬ 
phorus pentachloride or pentabromide resp. was normal, it 
followed that the subsequent action of potassium hydroxide on 
the brom acid, thus formed from lactic, was normal, while that 
of moist silver carbonate on the same brom acid was abnormal 
just as Walden finally decided. The correctness of the above 
reasoning Fisher also established as follows by direct experi¬ 
ment. 
d brompropionic acid •+ KOH-^ d lactic acid (— Zn salt) 
d brompropionic acid + Ag 2 0 - > 1 lactic acid (+ Zn salt) 
d brompropionyl glycin + Ag 2 0- > d lactic ester (Free acid obt. by 
hydrolysis gave negative zinc s£lt). 
The actions of ammonia and of nitrous acid (nitrous fumes) 
were held to be normal from a consideration of the following re¬ 
actions : 
d brompropionic acid -f- NH 3 ->- d alanin (dextrorotatory) 
d brompropionic ethyl ester -f- NH 3 -d alanin ethyl ester (dextro¬ 
rotatory) 
d alanin + N 2 0 3 ->- d lactic acid (Negative zinc salt) 
d alanin ethyl ester + N 2 0 3 - > d lactic ethyl ester (Free acid obt. by 
hydrolysis gave negative zinc salt). 
Walden had tried the action of ammonia on chlorsuccinic 
acid but failed to get asparaginic acid. Fisher, by repeating 
Walden’s experiment later, 7 was able to isolate a small amount 
of the amino acid in. this wav. This fact is quite significant 
since it serves to bring out another important point. The for¬ 
mation of mon amino acid, by the action of concentrated aqueous 
ammonia on the halogen substituted acids, never takes place 
alone as most writers seem to imply. We sometimes have di 
and triamino acids formed in this action (vide Heintz) 8 and 
since ammonia acts also as a weak base, as well as an amino 
compound, we ought to have a large or small amount of hydroxy- 
7 Fisher and Raske: Ber. 40, 1051-7. 
s Heintz: Ann. 156, 25; Ann. 136, 213-223. 
