McLeod—The Walden Inversion—A Critical Review. 513 
suits/ 6 obtained with, optically active phenyl chloracetic acid, 
which were entirely out of harmony with Fisher’s results ob¬ 
tained in the lactic acid series, as well as those of Walden in the 
malic acid series. McKenzie quickly seized upon Fisher’s 
double inversion idea as a means of explaining some of his ap¬ 
parently anomalous results (i. e. anomalous in the sense of not 
harmonizing with Fisher’s conception of the Walden inversion 
as proposed in 1907). He found that optically active mandelic 
acid, treated with phosphorous pentachloride and then with 
potassium hydroxide, yielded its antipode while successive 
treatment with phosphorous pentachloride and oxide of silver 
gave back the same optically active mandelic acid as was used 
at the start. To obtain a harmonious explanation of these re¬ 
sults, McKenzie, in his second article, 27 held that the action of 
phosphorous pentachloride might be considered as abnormal in 
this case; the action of potassium hydroxide would then be nor¬ 
mal and that of silver oxide abnormal just as Fisher and Wal¬ 
den found in other series. But this assumption (that phosphor- 
our pentachloride may act abnormally) did not harmonize with 
the following observations by the same author. 
d mandelic + PC1 5 -^ laevorotatory d phenyl chloracetic 
ethyl d mandelate + PC1 6 ->- laevorotatory d phenyl chloracetic ethyl 
ester. 
He was forced to interpret, therefore, that silver carbonate 
acted normally, just as it may in Fisher’s experiment with opti¬ 
cally active valin, and that the action of potassium hydroxide was 
abnormal. These results- are exactly the opposite of those ob¬ 
tained by Fisher and Walden in the lactic and malic acid series 
respectively. McKenzie found also that the action of water 
was abnormal comparable to the action of strong bases on halo¬ 
gen acids of this series while Walden found that the action of 
water was similar to that of silver oxide and other weak bases. 
When phenylamino acetic acid was treated with nitrosyl bro¬ 
mide and the resulting brom acid treated with ammonia, the 
original amino acid was recovered. McKenzie explained this 
26 J. L. Ch. Soc. [May 1908] Vol. 93, p. 81. 
27 J. L. Ch. Soc., May 1909, p. 777. 
