RECENT WORK IX AGRICULTURAL SCII'XCE. 



AGRICULTURAL CHEMISTRY— AGROTECHNY. 



The chemical nature of the " vitamins." — I, Antineuritic properties of the 

 hydroxypyridines, R. H. Wji.liams {Jour. Biol. Chem., 25 (1916), No. 3, pp. 

 JfSy-Jf.'io). — The author has prepared the following pyridine derivatives and 

 tested their therapeutic action on polyneuritic pigeons by intramuscular in- 

 jection of doses of from 1 to 10 mg. : Nicotinic, cinchomeric, quinolinic, 6- 

 hydroxynicotluic and citrazinic acids, a-hydroxypyridine, glutazin, 2-, 4-, 6-tri- 

 liydroxypyridine and its anhydrid, and 2-, 3-, 4-trihydroxypyridine and the so- 

 called tetrahydroxypyridine. 



Of these substances definite evidence of curative power was noted only In 

 the case of a-hydroxy-, 2-, 4-, 6-trihydroxy-, and 2-, 3-, 4-trihydroxypyridine. 

 The remainder of the series showed no effect whatever, although it is deemed 

 that such negative evidence in the case of any hydroxy derivatives can not be 

 regarded as conclusive. It was noted that all the cures obtained were of those 

 pigeons which were treated with freshly prepared materials, while those 

 treated with the same preparations a few days or weeks later invariably re- 

 ceived no benefit. The substances were evidently changed in some manner so 

 as to lose their curative power, although no deterioration was evident. The 

 existence of a tautomerism in the hydroxypyridines suggested itself as being 

 of some interest in this connection. 



Following this suggestion it was found that a granular and a crystalline 

 needle form of o-hydroxjrpyridine could be prepared, both of which melted 

 sharply at from 106 to 107° C. After proper purification by remelting, keeping 

 well above the melting-point temperature for some time, and then allowing to 

 cool slowly, the mass was found to consist largely of needles. By recrystalliza- 

 tion from benzene with ligroin it was sometimes possible to obtain the needles 

 free from any granular crystals. On allowing the solid needle form to stand 

 for a few days in an open vessel or cork-stoppered bottle it was observed that 

 the crystals had undergone a change. The original clear and sharply defined 

 needles were marked by tran.sver.se lines of cleavage. The rate of the change 

 was variable but apparently depended on the amount of moisture in the atmos- 

 phere surrounding the crystals. Neither of these forms was found to absorb 

 appreciable amounts of bromin instantaneou.sly when titrated in the cold with 

 alcoholic bromin, so that neither form could have been the hydroxy or enol 

 form. On dissolving either form in an excess of alcoholic NaOH of known 

 strength an in.stantaneous absorption of bromin in excess of that require<l by 

 the alkali occurred. 



" It appears that there exist not two but three isomeric forms of o-hydroxy- 

 pyridine. ... By simple means we may cause any desired form to predomi- 

 nate and may pass through the cycle repeatedly. Each exists in equilibrium 

 with at least one other in relative quantities depending on condition.s. We shall 

 understand their relationships fully only after finding a method for determin- 

 ing each of the three forms quantitatively under varying conditions. At pres- 

 ent we can measure only the amount of enol." 



711 



