July 7, 1923 
Acid Production in Decaying Sweet Potatoes 
11 
an agreeable odor suggestive of pineapple, indicating the presence of 
butyric acid. The barium salts that were insoluble in alcohol were taken 
up in water, filtered free from the small amount of insoluble carbonates 
and decomposed by an excess of sulphuric acid. The barium sulphate 
was removed by filtration and the volatile acids removed by distillation 
from the filtrate. Tests for the identification of the acids were made 
on this distillate or on the sodium or barium salts obtained from it. 
The reaction with ferric chlorid was positive for acetates and formates. 
With silver nitrate, a white crystalline precipitate, soluble in ammonia, 
was produced. On standing, or more promptly on heating, the pre¬ 
cipitate acquired a dark tint, but the separation of metallic silver causing 
it was always small. Mercurous nitrate produced a white crystalline 
precipitate which also took on a grayish tint on standing or on heating. 
Mercuric chlorid gave a white precipitate of mercurous chlorid on heat¬ 
ing, but its volume was very small for the amount of salt tested. Heated 
with sulphuric acid the salts gave off the odor of acetic and formic acid. 
Slight effervescence accompanied the reaction, yielding a gas which 
in carefully carried out tests could be ignited, burning for an instant 
with a blue flame. The ester obtained on heating the salt with sulphuric 
acid and alcohol suggested both methyl and ethyl acetates, in comparison 
with parallel tests on pure known salts alone and combined. The free 
acids were warmed at 45 0 C. with an excess of mercuric oxid, filtered, 
and the filtrate heated to boiling; a slight but distinct precipitate of me¬ 
tallic mercury was thrown down. White crystals of acetate of mercury 
appeared in the liquid on cooling. The sodium salt heated with para- 
toluidin and hydrochloric acid yielded an acid toluid which when purified 
and twice recrystallized melted at i45°-i46° C., uncorrected. Acet- 
p-toluid melts at 148.2°C., corrected. A portion of the barium salts 
was purified by twice redistilling from strong sulphuric acid and again 
obtained as the barium salt. After recrystallization the barium content 
of the dehydrated product determined gravimetrically by precipitation 
with sulphuric acid was 53.53 per cent. A synthetic sample prepared 
from pure glacial acetic acid and the barium hydrate used in the work 
also yielded an average of 53.53 per cent of barium. The theoretical 
figure for pure barium acetate is 53.79 per cent barium. 
From the foregoing tests it is evident that the volatile acid obtained 
was chiefly acetic but that a small amount of formic and a trace of butyric 
were also recovered. 
The ether extract was examined for nonvolatile acids. On standing 
fine needle crystals appeared in the sirupy matrix remaining after 
evaporation of the ether. Water was added and the resulting solution 
titrated against phenolphthalein with standard barium hydrate, 50 
to 60 cc. of N/10 solution being required. The resulting barium salts 
were evaporated to dryness, triturated with 10 to 12 cc. of water, 
filtered, washed with a few cubic centimeters of water, and the filtrate 
and wash water treated with strong alcohol till the concentration was 
90 per cent by volume. It was then placed in the ice box for a day or 
two, after which the precipitate was filtered off and washed with alcohol. 
The filtrate was evaporated to a small volume, diluted with 20 cc. of 
water and carefully treated with N/10 sulphuric acid, drop by drop, 
as long as calcium sulphate precipitated. The excess sulphuric acid 
added was removed by one or two drops of barium hydrate solution 
and the barium sulphate removed by filtration and washed. The 
filtrate and washings were evaporated on the water bath to a small 
