1394 FOODS AND FOOD ADULTERANTS. 



from the first distillation, evaporate it to small volume on the water 

 bath, acidify with sulphuric acid, avoiding a great excess, and extract 

 with several portions of ether. Remove the ether from the extract 

 by means of distillation or evaporation and test the nonvolatile residue 

 with Millon's reagent. The formation of the red color, either in the 

 cold or on gentle warming, indicates the presence of aromatic oxyacids. 

 In applying the above method the following precautions must be 

 observed: First, it is.not practicable in the presence of aromatic pre- 

 servatives, such as salicylic acid; second, great care must be taken, 

 especially with fish, that no intestinal contents be present in the 

 sample under examination; third, in examining meat that is exposed 

 to the air the surface should be rejected, since it is possible that decom- 

 position may have begun at the surface without rendering the meat 

 unwholesome. 



DETECTION OF PTOMAINES." 



The material is divided as minutely as possible, placed in a large flask, and treated 

 with twice its volume of 90 per cent alcohol, and acidulated with tartaric acid in the 

 proportion of 0.5 gram to 100 cc of the mixture, taking care from time to time that 

 the reaction is permanently acid. The flask, which is connected with a reflux con- 

 denser, is now placed on the water bath and kept at the constant temperature of 70 

 for twenty-four hours. While yet warm the liquid is transferred to a special appa- 

 ratus for filtration by the aid of atmospheric pressure. The liquid is poured upon a 

 wet cloth, supported upon a perforated porcelain funnel, which is connected below 

 with a receiver exhausted by a vacuum pump. In this way rapid filtration is secured, 

 and by repeated washing the extraction is made thorough. The acid alcoholic liquid 

 is now transferred to a special distillation apparatus. 



A large tubulated retort of 10 liters capacity is connected by means of a cork to a 

 large tubulated receiver. The tubulure of the retort ie provided with a small per- 

 forated cork, which carries a glass tube finely drawn out and extending to the bot- 

 tom of the retort. The tubulure of the receiver is connected with Leibig's bulbs 

 containing dilute sulphuric acid (1 to 10), and the bulbs in turn are connected 

 with a vacuum pump. 



In order to prevent the passage of air through the corks they are covered with 

 animal membrane which has been freed from fat. By means of the aspirator a fine 

 current of air is drawn through the liquid and suffices to keep it constantly agitated. 

 The retort is kept on the water bath at a temperature of from 28 to 30. The 

 receiver is kept cold by a current of water. In this manner the distillation of the 

 alcohol goes on rapidly and conveniently. Moreover, decomposition is so far pre- 

 vented that volatile bases are never found in the bulbs. 



The aqueous residue, after the removal of the alcohol by distillation, is filtered and 

 extracted with ether as long as anything is dissolved. It is then mixed with powdered 

 glass and evaporated to dryness in vacuo. This residue is repeatedly extracted with 

 absolute alcohol. The alcohol is distilled again in the apparatus already described. 

 The residue is taken up with sodium bicarbonate and repeatedly extracted with 

 ether, benzin, and chloroform. 



In order to obtain the base from the solvent the greater part may be evaporated 

 on the water bath and the remainder allowed to evaporate spontaneously, or the 

 remainder may be treated with dilute hydrochloric acid and the evaporation con- 

 tinued on the water bath or in vacuo. 



a The Stas-Otto method modified by Selmi and Marino-Zuco; Vaughan and Novy, 

 Ptomaines, Leucomaines, etc., 3d edition, p. 265. 



