VITAMIN D 311 



not seem to be due to the production of ultra-violet light. (Compare 

 Bills and Brickwedde, 1928.) 



Using ergosterol ( [aji" = -132° in CHCU), Bills and Honeywell 

 (1928) and Bills, Honeywell and Cox (1928) studied the effect 

 upon the antirachitic potency of the product of irradiating for 

 different periods of time. Irradiation was conducted on a 1 per cent 

 solution (in 95 per cent alcohol) in a completely filled cell 2 centimeters 

 deep, placed in contact with the window of a Kromayer lamp, for 

 intervals of 7.5, 15, 22.5, 30, 45 minutes, and 1, 2, 3, 4, 5, 7.5, 10 and 

 15 hours. 



In the original ergosterol very well-defined absorption bands ap- 

 peared at 270 and 282 ///i with a less defined band at 293.5 fx,u, and no 

 antirachitic potency was evident. During the first 22.5 minutes, they 

 found that the antirachitic potency rapidly increased until it became 

 about 250,000 times as great as that of a good grade of cod-Hver oil, 

 with but a slight lowering of the maxima of both of the absorption 

 bands and with a broadening of the 270 /nfi band. With longer irradia- 

 tion, the antirachitic potency steadily declined ; the band at 282 dis- 

 appeared, and the band at 270 /nju shifted until a new band appeared 

 with a maximum at 248 jufi, accompanied by almost complete disappear- 

 ance of antirachitic potency. They conclude, therefore, that the photo- 

 chemical reaction product which exhibits the absorption bands at 248 fifi 

 is not vitamin D, as some investigators had thought, but is a by-product 

 of the vitamin. The wave-lengths which vitamin D itself absorbs and by 

 which it is destroyed, apparently lie within the same spectral region as 

 the wave-lengths which activate ergosterol. Clearly the spectroscope 

 cannot replace the feeding method of studying the formation of 

 vitamin D. 



Oxidation appeared to be involved in the destruction but not in the 

 formation of vitamin D. 



These authors suggested that the substance having the absorption 

 band at 248 ,m/i is iso-ergosterol. This same suggestion has been made 

 by Van Wijk and Reerink (1928). 



Windaus and coworkers (1929) reported that the effect of the 

 solvent on the antirachitic potency of irradiated ergosterol is small, 

 provided the solvent allows the ultra-violet light to pass through it. 

 Cyclohexane, ether and benzene were used as solvents by these inves- 

 tigators. 



Bills, Honeywell, Cox and Wirick (1929) found, however, that 

 the solvent had a very great influence on the potency of the prod- 

 uct of irradiation. Alcohol, ether and cyclohexane were used. 



