Nov. 24,1923 
Studies on Rancidity 
327 
hydrochloric acid reagent, since these tests are probably the two most 
dependable and widely used criteria of the rancid condition. No rigorous 
purification of these compounds was attempted, on the principle that 
the presence of an impurity, even in appreciable amounts, would be 
more apt to add to, than to detract from, the odor and reactivity of the 
substance under examination. In each case the tests were made both 
on the substance itself and on a perfectly sweet fat to which the sub¬ 
stance had been added. 
The Kreis test for rancidity was performed as follows : 
Five cc. of fresh fat to which the compound to be examined had 
been added, or a few drops of a dilute ethereal or aqueous solution of 
the compound itself, were shaken with 5 cc. of concentrated hydro¬ 
chloric acid. The mixture was then shaken with 5 cc. of a 1 per cent 
ethereal solution of phloroglucin. The development of a typical red 
color in the hydrochloric acid was regarded as constituting a positive 
reaction. 
While it was not anticipated that the fatty acids would respond to 
the Kreis test, the test was carried out as a routine procedure in all 
cases. 
Hydroxystearic acid. —Hydroxystearic acid was prepared by the 
method of Saytzeff (55). Considerable difficulty was experienced in 
purifying the crude product, but by holding its ethereal solution at a 
temperature below o° C. for several days a separation of impure crystals 
was obtained, after which the product was further purified by recrystalli¬ 
zation, once from ether, twice from alcohol, and twice again from ether. 
The material thus obtained was in the form of small, white, somewhat 
lustrous crystals, melting at 79 0 C. as compared with the reported melt¬ 
ing point of from 83° to 85° C. for pure hydroxystearic acid. The sub¬ 
stance proved to be odorless and failed to respond to the Kreis test, 
whether tested by itself or in the presence of a nonrancid fat. 
Dihydroxystearic acid. —Dihydroxystearic acid was prepared by the 
method of Saytzeff (34). The raw product was recrystallized from hot 
alcohol several times, whereby a white crystalline material was obtained 
which melted at 129.8° C., as compared with the melting point of 136.5° C. 
reported for the completely pure substance. Dihydroxystearic acid 
proved to be odorless, and failed to respond to the Kreis test, as did also 
a nonrancid lard to which it had been added. 
Ketoxystearic acid. —Holde and Marcusson (18) were able to recover 
a small amount of ketoxystearic acid from the products formed when 
oleic acid is oxidized with potassium permanganate in presence of a 
single equivalent of alkali instead of the large excess of alkali employed 
m the preparation of dihydroxystearic acid. An attempt to prepare 
this substance in the manner described by Holde and Marcusson was not 
successful. 
While in view of its ketone group, this compound was among those 
originally thought of as being responsible for the behavior of rancid fats 
in the Kreis test and as contributing toward the rancid odor, no further 
attempt was made to prepare ketoxystearic acid, since the negative 
result^ obtained meanwhile with the closely related diketostearic acid, in 
comparison with which the ketoxystearic acid should be less odorous 
and less reactive, seemed to indicate that the latter product also must be 
odorless, and negative in its reaction with the Kreis reagent. 
Diketostearic acid. —The preparation of diketostearic acid was first 
attempted by the method of Overbeck {28), but as satisfactory results 
