proceedings: chemical society 229 



temperatures were obtained by steam under pressure and the hydroly- 

 sis occurred without caramelizatibn. It is necessary to choose the 

 sugar and water with considerable care. A temperature of 124°C., cor- 

 responding to a pressure of 1.375 kg. above atmospheric, was found to 

 give the best results under the conditions of the experiment. (Author's 

 abstract.) 



Discussion. Phelps pointed out the possibility that the change 

 in the rate of hydrolysis might be due to the change in H ion concen- 

 tration. Hudson spoke of CO2 under pressure as an agent for_ the 

 inversion of sugar and the fact that it is generally regarded as a strictly 

 mechanical effect. Johnston pointed out that the effect of pressure 

 alone on reacting solid or Kquid systems is greatly overestimated, the 

 temperature and concentration being the important factors. Accord- 

 ing to Phelps, in these experiments,, pressure increase alone had no 

 effect on the rate of hydrolysis. Hudson spoke of the work of Spring 

 as showing the effect of pressure on heterogeneous systems containing 

 no gas phases. Johnston said that Spring's evidence was very poor 

 and that the strictly pressure effects were verj^ small in cases of true 

 equilibria. 



H. C. Gore, of the Bureau of Chemistry: The concentration of apple 

 juice by freezing. By freezing, centrifuging to remove the ice and 

 filtering through infusorial earth, apple cider was concentrated to 50 

 per cent total solids at a cost of 20 cents per gallon of concentrated 

 juice. This juice can be kept without adding preservative. Other 

 fruit juices have been concentrated in the same way. 



Discussion: Hudson inquired whether the juice was filtered before 

 or after concentration. Speaker stated that the filtration could be 

 carried on as easily after as before and was generally done in that way. 

 Berg inquired as to the use of centrifugal filters. Speaker stated that 

 these were found lacking because no suitable clarifier had been found 

 while infusorial earth was entirely satisfactory. 



The 245th meeting was held at the Cosmos Club on Thursday, Feb- 

 ruary 11, 1915. Dr. Johnston on behalf of the committee on com- 

 munications briefly announced a new policy in regard to the programs 

 for the meetings. The aim being to make the programs of wider 

 scope in their interest, the main material- is to be furnished on invi- 

 tation from the committee. In addition it is proposed to have short 

 informal communications, each limited to five minutes. As far as possi- 

 ble it is desired that these informal communications have some bearing 

 on the general topic under discussion. 



Carrying out the above policy the following papers were presented : 

 F. E. Wright, of the Geophysical Laboratory: The petrographic micro- 

 scope in analysis. Attention was directed to the fundamental differ- 

 ence between a petrographic microscope and an ordinary microscope. 

 The latter is essentially a magnifier and serves to render visible minute 

 objects and details which are then recognized by their shape, size, 

 and color. In the case of bacteria the differences in behavior with 



