PUTREFACTION PRODUCTS OF PROTEIDS. 167 



REMARKS. The oily residue remaining after distilling 

 the ether extract (F), which contains volatile acids, oxyacids, 

 skatol-carbonic acid, and succinic acid, is placed in a flask 

 and distilled in a rapid current of superheated steam. The 

 steam is superheated by passing it through a gently heated 

 copper spiral. 1 This should not be heated too strongly, as 

 the skatol-carbonic acid will then be resinified to a considera- 

 ble extent. This resinification cannot be entirely avoided, 

 however, in any case. The vapors are conducted directly 

 into sodium hydroxide solution, which, of course, becomes 

 quite hot. 



It is well not to have the current of steam too strong at 

 first, as then too much of the acid escapes unabsorbed. The 

 previous treatment of the distillation residue gives sufficient 

 data to estimate the quantity of sodium hydroxide solution 

 to be placed in the receiver; use about the quantity which 

 was needed to make the first acid ether extract alkaline. To 

 drive over the volatile acids completely requires considerable 

 time, twenty-four to thirty-six hours. As a criterion we 

 make use of the conduct of a very weak alkaline fluid (con- 

 taining 1 to 2 cc. one- tenth normal sodium hydroxide), 

 placed in a receiver: if this fluid still remains alkaline after 

 an hour, the distillation is to be regarded as completed. 



The entire alkaline solution is evaporated on the water- 

 bath and, after it is cold, strongly acidified 2 with hydro- 

 chloric acid and extracted with ether. The residue left after 

 distilling the ether extract is distilled from a flask provided 

 with a thermometer. The volatile fatty acids distil first. 

 The receiver is changed when the temperature has risen to 

 about 260 and the distillation is continued until only a very 



1 Zeitschr, f. physiol. Chemie, 9. 493 



2 To detect the presence of free hydrochloric acid test the reaction of 

 a few drops of the fluid, after the first extraction with ether, with methyl 

 violet. 



