CHEMISTRY. 351 



requires several months, and measurements made in infected ceils 

 are not regarded as reliable. An interesting phenomenon observed 

 in connection with infected cells whose membranes have not yet 

 become "leaky" is the development of abnormally high pressures. 

 In fact, the development of too high pressures is one of the earliest 

 symptoms of infection. The explanation is, of course, that the 

 products of PeniciUium activity serve to increase the concentration 

 of the solutions. 



It was stated in the report of last year that it had always appeared 

 important to the writer and to those associated with him to extend 

 the scope of their work so as to include a simultaneous determination 

 of the vapor-tension of the solutions under investigation; also that 

 Doctors Frazer and Lovelace had succeeded in developing a practi- 

 cable method of great precision for this purpose. Preliminary accounts 

 of their method have been published in the Journal of the American 

 Cheinical Society. During the past year, assisted by Messrs. Sease 

 and Rodgers, they have investigated the vapor-tension of the following 

 solutions: (a) of mannite from 0.1 to 1.0 weight normal; (6) of sodium 

 chloride from 0.1 to 3.0 weight-normal concentration. 



The most striking development of the year has been the success 

 attained by Dr. Frazer, assisted by INlr. Myrick, in the measurement 

 of very high osmotic pressures. The method in the form in which it 

 has been employed hitherto is satisfactory up to perhaps 60 atmos- 

 pheres. Under greater pressures the cells frequently burst. In 

 order to overcome this difficulty Dr. Frazer has reversed the method 

 of formation in such a manner as to deposit the membrane on the 

 exterior instead of the interior surface of the cell-wall. The cell is 

 placed within a bronze container of the necessary strength. The 

 solution occupies the space between the two, while the porous cell is 

 filled with water which is in communication with a supply of water 

 under atmospheric pressure. The manometer is attached to the bronze 

 container. With such an arrangement pressures up to 125 atmos- 

 pheres have been measured satisfactorily. 



For pressures above 125 atmospheres, glass manometers no longer 

 suffice, and for such Dr. Frazer has constructed a device for measuring 

 osmotic pressure by means of the effect of pressure upon the conduc- 

 tivity of certain alloys. It consists, essentially, of a combination of 

 the Johnston modification of the Bridgman resistance-gage with the 

 Corey-Foster bridge and high-sensitivity galvanometer for the 

 measurement of resistance changes. This equipment, over a range of 50 

 atmospheres, is sensitive to about 0.02 atmosphere, and over a range 

 of 500 atmospheres the one in use has a sensitivity of about 0.05 

 atmosphere. The gage-readings are thought to be correct to about 

 0.2 atmosphere. With the arrangement in question Dr. Frazer and 

 Mr. Myrick have measured osmotic pressures up to 270 atmospheres. 



