184 BACTERIAL POISONS. 



blue, violet, then green with Frohde's reagent ; yellow 

 when evaporated with concentrated sulphuric acid, then 

 treated with hydrochloric acid and decomposed with sodium 

 bicarbonate. The ptomaines reduce ferric chloride, but not 

 iodic acid. "With sugar and concentrated sulphuric acid, 

 they give a yellow coloration. 



Mixtures of the ptomaines and morphine give absolutely 

 characteristic reactions for morphine with sugar and sul- 

 phuric acid, the violet coloration appearing distinctly ; and 

 by evaporation on the water-bath with sulphuric acid, addi- 

 tion of hydrochloric acid and decomposition with sodium 

 bicarbonate, the violet color appearing. Iodic acid is re- 

 duced by morphine in the presence of ptomaines, only 

 when the ptomaines are present in minute quantity. 



The other reactions for morphine are not applicable in 

 the presence of ptomaines. 



Strychnine. — The characteristic color reaction for this 

 alkaloid, with potassium bichromate and sulphuric acid, is 

 not aifected by the presence of ptomaines.^ 



Brucine. — The nitric acid reaction for brucine is not 

 affected by ptomaines. On the other hand, the reaction 

 with sulphuric and nitric acids, in which a red coloration 

 is obtained, is scarcely visible in the presence of ptomaines. 

 The action of mercuric nitrate and heat on brucine, by which 

 a violet coloration is produced, is not destroyed by the 

 presence of ptomaines. 



Veratrine. — The characteristic coloration of veratrine 

 by concentrated sulphuric acid is not influenced by pto- 

 maines. The same is true of the cherry-red coloration with 

 concentrated hydrochloric acid. On the contrary, the action 

 of sugar and sulphuric acid on veratrine is without result 

 in the presence of ptomaines. 



Atropine. — The deep violet coloration produced by 

 fuming nitric acid, subsequent concentration, and the addi- 



1 In contradiction to this, see page 178. 



