296 CARNEGIE INSTITUTION OF WASHINGTON. 



difficulties seem now to have been mastered and it is hoped that Mr, Anderson 

 in a few months next winter may be able to complete the investigation. 



9. The Electrode Potential of Iron under Varying Conditions. 



Mr. William T. Richards studied the effect of hydrogen-ion concentration 

 and of powerful magnetic fields upon the electrode potential of metallic iron, 

 both in the pure state and when saturated with occluded hydrogen. The 

 investigation is completed and the results are almost ready for publication. 



10. Theoretical Considerations. 



Much time has been spent upon the study of the internal pressures of solids 

 based upon the recent results concerning compressibihties. The outcome 

 shows that in highly compact substances the volume-pressure relation is 

 essentially hyperbolic and that the pressures existing in such substances are 

 of a very high order of magnitude. The outcome had been used to calculate 

 actual changes of volume which occur in atoms during chemical combination. 

 Some of the results of these theoretical considerations have been correlated in 

 a paper presented to the Royal Swedish Academy in Stockholm in December. 

 An exhaustive discussion of the present status of atomic weights was presented 

 for publication in the volume commemorating the dedication of the new 

 Sterling Laboratory at Yale University. These papers have not yet appeared 

 in print; but four other papers have been published since the last report. 



Sherman, H. C, Columbia University, New York, N. Y, Chemical investi- 

 gation of the amylases and related enzymes. (For previous reports see 

 Year Books Nos. 11-21.) 



During the year four papers, dealing with different aspects of our investi- 

 gation of these enzymes, have been published in the Journal of the American 

 Chemical Society. A fifth paper of more general scope, summarizing the evi- 

 dence which we had obtained up to November 1922 in those phases of our 

 work which bear directly upon the problem of the chemical nature of these 

 enzymes, was read at the autumn meeting of the National Academy of Sci- 

 ences and has since been published in its Proceedings. 



The laboratory work of the year has been chiefly devoted to a further 

 development of the experimental evidence that enzymic activity is influenced 

 by amino acids in such a manner as to indicate that the enzyme is of protein 

 nature or contains protein as an essential constituent, and to the verification 

 of the hypothesis offered in last year's report to explain the differences shown 

 by representative amino-acids of different types. To this end the inactiva- 

 tion of pancreatic amylase in water solution has been investigated more 

 critically than hitherto and the two typical amino-acids, glycine and trypto- 

 phane, have been studied further with reference to their influence upon the 

 enzyme, both in the absence and in the presence of the substance upon 

 which it exerts its characteristic action. 



When the enzyme (pancreatic amylase) in the form of high-grade com- 

 mercial pancreatin was dissolved in pure water and held at a temperature 

 of 10° C, it lost about one-sixth of its activity in 4 hours and about half in 24 

 hours. At 25° C, it lost nearly half of its activity in 2 hours and about two- 

 thirds in 4 hours. At 40° C. the activity was entirely lost within an hour. 

 When the same enzyme preparation was dissolved in water to which had been 

 added sodium chloride and disodium phosphate in the proportions which we 



