48 THE VITAMINS 



preparations were never in definite crystalline form, although some 

 of them showed under the microscope a mixture of crystalline frag- 

 ments and amorphous material. 



deCugnac used acetone as a precipitant of vitamin B. Smith (1930) 

 on the contrary prepared a concentrate of vitamin B from the super- 

 natant fluid decanted from the precipitate obtained when 1 volume 

 of vitamin-rich solution was poured into 9 volumes of acetone. His 

 method was as follows : After triturating dried brewers' yeast in a 

 mortar with 5 volumes of twenty-fifth normal acetic acid, and allowing 

 it to stand overnight, the extract was centrifuged, decanted, and poured 

 with stirring into 2 volumes of 95 per cent alcohol. The supernatant 

 liquid was concentrated to one-twentieth its volume, poured into 9 

 volumes of acetone, and again the supernatant solution decanted and 

 concentrated to one-twentieth its volume. After diluting 10 times with 

 water (pH 4) it was stirred with purified norite 3 times, the norite 

 filtered and washed with water. The combined norites were treated 3 

 times successively on a water bath with 5 volumes of twentieth-normal 

 hydrochloric acid in 50 per cent alcohol. The extract thus obtained 

 was concentrated to one-twentieth of its volume under reduced pres- 

 sure, and was found curative to polyneuritic rats in single doses of 

 0.5 to 1.0 milligram soHds. 



A comparison of the relative potencies of various vitamin B con- 

 centrates by this method and by the Seidell method showed a decided 

 lack of agreement. Referring to the confusion arising from using 

 different tests, Smith emphasizes a point which cannot fail to impress 

 any one who attempts to review the long and as yet unsuccessful at- 

 tempts to isolate the antineuritic vitamin and determine its chemical 

 nature. "Apart from the question as to which of the two methods rep- 

 resents a more accurate index of the antineuritic potency of the above 

 or any other concentrate, these results at least emphasize one point 

 clearly, and that is the impossibiUty of comparing the merits of the 

 various chemical procedures used by different men in the concentration 

 and purification of the antineuritic vitamin unless one biologic method 

 is adopted in common for testing of the potency of such concentrates." 



Suggestions as to the Chemical Nature of the Antineuritic 



Vitamin 



As has been noted, attempts have been made from time to time 

 to assign empirical formulas to the antineuritic vitamin on the basis 

 of analyses and reactions of the concentrates prepared, and also to 

 determine the chemical nature of the vitamin by testing definite com- 



