October 14, 1921] 



SCIENCE 



359 



following: whether rickets is due to lack of 

 Fat Soluble A, whether there is an antiscor- 

 butic vitamine (Water Soluble C), and in 

 what sense pellagra may be rated as a defi- 

 ciency disease. All the material is handled 

 in a cautious and modest way with the result 

 that no encouragement is given to faddists 

 of any kind. 



Percy G. Stiles 



EXPERIMENTS ON THE RECORDING 

 AND REPRODUCTION OF CAR- 

 DIAC AND RESPIRATORY 

 SOUNDS 



We have recently conducted experiments 

 at the Bureau of Standards in which perma- 

 nent records of cardiac and respiratory sounds 

 have been made and reproduced by the use of 

 a telegraphone. The records have also been 

 made audible throughout the room with the 

 aid of audion amplifiers and a loud-speaking 

 telephone. 



A carbon telephone transmitter of ordinary 

 type with a rubber adapter substituted for the 

 mouthpiece was used for the stethoscope. 

 The currents from the telephone transmitter 

 were amplified by means of a five-stage audion 

 amplifier which was connected to the record- 

 ing element of a steel wire telegraphone. The 

 magnetic records of the cardiac and respira- 

 tory sounds thus obtained were made audible 

 by connecting telephone receivers to the 

 telegraphone in the usual manner. The tele- 

 graphone currents were also amplified by 

 means of a three-stage audion amplifier 

 which was connected to a loud speaking tele- 

 phone. In this way the sounds were made 

 audible throughout the room. 



This method of obtaining permanent rec- 

 ords of cardiac and respiratory sounds and 

 of reproducing them offers interesting pos- 

 sibilities in the study of normal and patholog- 

 ical conditions of the heart and lungs and 

 their demonstration to an audience for pur- 

 pose of instruction. 



Franklin L. Hunt 



Bureau of Standards 



Magnus J. Myres 

 Medical Corps, XJ. S. A. 



SPECIAL ARTICLES 



THE SEPARATION OF THE ELEMENTS CHLO- 

 RINE AND MERCURY INTO ISOTOPES 



In Science of March, 1920, Harkins and 

 Broeker reported that they had obtained a 

 separation of chlorine into isotopes by dif- 

 fusing hydrogen choride gas. The separation 

 at that time amounted to an increase of 

 atomic weight equal to 0.055 unit, or a 

 change of density amounting to 1,550 parts 

 per million. This separation has been defin- 

 itely confirmed by Dr. Anson Hayes and the 

 writer, who have secured an increase of 0.04 

 unit of atomic weight in a larger quantity 

 of material. Elaborate purifications have been 

 resorted to, and definite evidence has been 

 secured to show that the increase in density 

 found is actual, and not due to impurities. 

 The details of this work were supposed to 

 have been printed in the August number of 

 the Journal of the American Chemical So- 

 ciety. However, since the date of publication 

 of this number is doubtful on account of the 

 printers' strike, it seemed advisable to answer 

 here the considerable number of inquiries as 

 to whether we have secured definite evidence 

 of the separation. 



About six months after our notice of the 

 separation of chlorine into isotopes had been 

 published, Bronsted and von Hevesy pub- 

 lished a notice in Nature indicating that they 

 had separated mercury into isotopes. How- 

 ever, since the extent of the density change 

 reported by them was only about one thirtieth 

 of that previously obtained by us in the case 

 of chlorine, it seemed to us that the evidence 

 for this separation of mercury was incon- 

 clusive, since a change of 50 parts per million 

 in density might be due to minute amounts of 

 impurities. In order to see if they could con- 

 firm these results. Dr. E. S. Mulliken and the 

 writer have vaporized mercury at low pres- 

 sures. The mercury was carefully purified 

 by five fractional distillations in air at low 

 pressures, and one in a high vacuum, after 

 initial purifications with nitric acid. The 

 increase in density obtained amounts to 69 

 parts, and the decrease to 64 parts or a total 



