EVOLUTION OF GASES FROM HOMOGENEOUS LIQUIDS. 



281 



collected over water ; the whole process waa therefore continuous, with the exception 

 of the interval during which the gas filled up the vacuum, or was pumped out while 

 the pressure was being reduced. 



A. mixture was made up as follows : 



Sulphuric acid . . . . = 175 c.c. 



Water = 58 



Solution of sodium formate = 75 



containing 10 grams of the salt in solution, which corresponds to 330 observations 

 of 10 c.c. each ; thus, the difference between successive observations caused by 

 diminution of mass and dilution of the sulphuric acid by the water formed in the 

 reaction is inappreciable. 

 Temperature 69-69 0> 2. 



The results set forth in the above table are practically continuous ; when it was 

 judged that the maximum and constant rate in Series I. was attained, the pressure 

 was suddenly increased by temporarily taking out the cork of the flask containing 

 the acid mixture, and the observations in Series IT. commenced ; the interval of time 

 between the last observation of I. and the first of II. was 12 minutes, but during this 

 time little, if any, gas was given off. Again, when in Series II. the maximum and 

 constant rate was reached, the pressure was reduced as rapidly as possible to the 

 former point by working the SPRENGEL, a process requiring about 8'*5, during which 

 the pumped-out gas was allowed to escape. The results show that at the reduced 

 pressure there is the usual period of initial acceleration ; on increasing the pressure 

 there is a retardation followed by an acceleration, but on again decreasing the 

 pressure the phenomenon is reversed, i.e., there is a period of initial retardation. The 

 intervals of time in the period of maximum rate of Series I. are slightly less than those 

 in Series IL, but these latter are equal to those in Series III., thus showing that 

 variations of pressure produce but little variation in the rate of evolution of gases 

 from liquids. It is also to be noted that, as regards the initial acceleration, the effect 

 of a sudden increase of pressure is precisely the same as that of a temporary lowering 

 of temperature. 



MDCCCLXXXVIII. A. 2 O 



