BACTERIAL CELLULAR SUBSTANCE 91 



valin as 298, corrected, when heated in a closed tube, 

 decomposition taking place at the same time. The valin 

 from the tubercle poison melted as high as 296.28, cor- 

 rected, but after continued recrystallizations the melting- 

 point dropped as low as 285, and was never reliable. 

 Whether this was due to a partial racemization on repeated 

 heating is not known. Heated in a closed tube the melting- 

 point of the final product was 275.8 to 278.2. As is well 

 known, valin closely resembles leucin in its properties, so 

 that it is very difficult to demonstrate the existence of one in 

 the presence of the other. On page 78, by another method, 

 the presence of leucin in the poison has been shown, but 

 by the Fischer method of ester distillation valin seems to be 

 the one obtained. The presence of leucin was further 

 demonstrated by the fact that from the final residue left 

 after the esters had been distilled, crystals of its decomposi- 

 tion product, leucinimide were obtained. This crystallized 

 from dilute alcohol in the form of needles and melted at 

 295.4. Cohn gives the melting-point of leucinimide as 295, 

 Frankel as 262. From fraction 5 of the tubercle poison a 

 qualitative test only was obtained for phenylalanin, the 

 quantity obtained being too small for complete purification. 

 After evaporation of the ethereal solution of the thick, 

 oily ester, according to the method, the ester is saponified 

 by twice evaporating with hydrochloric acid. It is then 

 evaporated with ammonia, dissolved in a small amount of 

 water, and poured into a large volume of absolute alcohol, 

 which precipitates the phenylalanin. From this precipitate 

 the qualitative test was obtained, according to Frankel, 

 by dissolving in dilute sulphuric acid and adding an excess 

 of potassium dichromate, producing the characteristic 

 odor of phenylacetaldehyde and showing thus the presence 

 of phenylalanin. From fraction 5, after removal of the 

 phenylalanin, upon saponification with barium hydrate, 

 there was obtained, after the barium had been removed, 

 rhombic hemihedral crystals which had a distinctly sour 

 taste. These, after purification, showed 9.54 per cent, of 

 nitrogen, the average of two Kjeldahl determinations, 



