596 



SCIENCE 



[N. S. Vol. XLVI. No. 1198 



Table V. contains the results of sucli a test 

 for air as the source of ions in a brass tube 

 of 2.95 cm. diameter and .300 mg. of radium 

 salt as the ionizing agent placed at a distance 

 27.Y cm. from the electroscope and approxi- 

 mately 1 cm. above the slit. 



Table VI. gives results obtained for X-rays 

 as ionizing agent, the slit being placed 27.7 

 cm. from the electroscope, with an air velocity 

 in the brass tube of 2.95 cm. diameter. Table 

 VII. records values for an X-ray ionizing 

 source at 125.3 cm. from the electroscope, 

 other experimental conditions remaining the 

 same. 



TABLE VII 



The lack of saturation in the electroscope 

 for large ionization currents would tend to 

 give too small a value for the recombination 

 constant, while diffusion effects at the smaller 



velocities through the tube would increase it. 

 Neither of these causes, under the experi- 

 mental conditions, would appear to be suffi- 

 cient to explain the larger values obtained 

 for the recombination constant for the more 

 penetrating radiations. 



I am indebted to the Providence Gas Co. for 

 the gas meter which was used, also for its care- 

 ful calibration before and after the experi- 

 ments. 



P. B. Perkins 



Brown XJNnfERSiTT, 

 June 28, 1917 



BOSTON MEETING OF THE AMERICAN 

 CHEMICAL SOCIETY. Ill 



DIVISION OP BIOLOGICAL CHEMISTRY 



C. L. Alsberg, Chairman 

 I. K. Phelps, Vice-cJiairman and Secretary 

 The relation of the dissociation of hydrogen to 

 enzymatic activity: Howard T. Graber and J. W. 

 M. Bunker. It was demonstrated that the enzyme 

 ' ' pepsin, ' ' in agreement with the other enzymes, 

 iuvertin and catalase, has an optimum at a definite 

 H. ion concentration and that the presence of 

 other ions exerts an influence which is not measur- 

 able, yet not negligible. It was shown that in the 

 ease of the weakly dissociated organic acids the 

 buffer effect of the protein added has a marked 

 effect upon the dissociation of the acids, but that 

 when 'the concentration of the H ions was made 

 equal to that of 3 per cent. HCl by considering 

 temperature and protein the organic acids are 

 equal to 3 per cent. HCl as activators for peptic 

 digestion. 



On the origin of the hiimin formed by the acid 

 hydrolysis of proteins III. Hydrolysis in the pres- 

 ence of aldehydes II. Hydrolyis in the presence 

 of formaldehyde: Koss Aiken Gortner and 

 George E. Holm. Hydrolysis in the presence of 

 formaldehyde completely alters the nitrogen distri- 

 bution obtained by Van Slyke's method. Black 

 insoluble humin is formed from tryptophane and 

 no other known amino acid is concerned in the re- 

 action. The primary reaction of black humin for- 

 mation involves only the indole nucleus and not the 

 a amino group of the aliphatic side chain of trypto- 

 phane. Formaldehyde forms a soluble humin with 

 tyrosine which is precipitated by Ca(0H)2. Hy- 

 drolysis in the presence of formaldehyde causes 

 enormous increases in the ammonia fraction, but 

 the increase is not due to ammonia, but to volatile 



